Atlas of neurosurgical anatomy the pterional perspective springer verlag new york

Atlas of Neurosurgical Anatomy

John L. Fox

Atlas of Neurosurgical Anatomy The Pterional Perspective With a Contribution by Bengt Ljunggren Illustrated by David M. Klemm

With 171 Illustrations in 329 Parts, 133 in Full Color

Springer-Verlag New York Berlin Heidelberg London Paris Tokyo

JNtN L. Fox, M.D. Clinical Professor of Surgery. Division of Neurosurgery, Uni"ersity of Nebraska Medical Center, Omaha, NE68105, USA H ENGT LJUNGGREN, M.D.

Professor. Department of Neurosurgery, Uni,'e rsity Hospital, Uni,'c rsity of Lund, 22185 Lund,Sweden

Illttilmtor D AV ID M.

K L EMM

Medical lIIustralOr. Ed ucational l\ledia Production and Services. GeorgelOwn University Medical Center, Washington, DC 20007, USA Portions of the wor k on this atlas were carried OUI by Dr. J. L. Fox at the following institutions: Universi ty of Zurich, Zurich, Swiuerland (1973-1974); West Virginia University Med· ical Center. Morgantown. West Virginia (1975-1982); King Faisal Specialist Hospital and Research Centre, Ri yadh, Saud i Arabia (1983-1985); Georgetown Unil'ersity Medical Center, Washington. D.C. (1985-1987); and University of Nebras ka 1-.ledica l Center. Omaha, Nebraska (1987 -1988). The senior author is grateful for their support in this academic en· d eavor.

On IM/TQnl coveT: Fig. 7. 13/p. 138. Library of Congress Cataloging-in-Publication Data Fox, J ohn L., 1934Atlas of neurosurgical anatomy: the plerional perspective f J ohn L. Fox with a contribution by Hengl Ljunggren ; illustrated by David M. Klemm. p. cm. Includ es bibliographies and index. \. Brain-Anatomy-Atlases. 2. Brain-Surgery- Atlases. [. Ljunggren, SengI. II. Title. [DNLM: !. Nervous Syslem-anatomy & histology-atlases. 2. Nen'ous System-surgery-atlases. WL 17 F792aJ QM455. F65 1989 61 1.8-dcl9 DNLMIDLC 88·39319 Printed on add·free paper o3:l 1989 by Springer-Verlag New \orlo: Inc. Softcovcr repri nt oTlllc hardcover 1st edition 1989 All rights reserved. This work may not be trans lated or copied in wbole or in pan without the writlen permission or the publisher (Springer-Verlag, 175 Fifth A"enue, New York, NY 100 [0. USA), except for brief excerpts in connection with reviews or scholarly analysis. Use in connection with any form of information storage and retrieval, electronic adaptation, computer software, or by similar or d issimilar methodology now known or hereafte r de· "e1oped is forbidden. The use of general descriptive names, trade names, trademarks, etc. in this publication, even if the former are not especiaJl ~' identified, is not to be taken as a sign that such names, as understood by the Trade Marks and Merchandise Marks Act, may accordingly be used freely by anyone. While the advice and information in this book are believed to be trueand accurate althe date of going to press, neilher the authors nor the editors nor the publisher can acce pt any legal responsibility for any errors or omissions that may be made. The publisher makes no ,,'ar· ranty, express or implied. wi th respect to the material contained herein.

Typeset, printed, and bound by Universitatsdruckerei H. Sturtz AG. Wunburg, Federal Republic of Germany.

9 8 765 4 3 2 1 e-[SBN-1 3: 978-1-4613-8823-4 lSBN- 13: 978-1-4613-8825-8 00[: 10. 1007/978-1-46 13-8823·4

Dedicated to James Winston Watts, M.D., Professor Emeritus, Department of Neurological Surgery, George Washington University Medical Cente'r, Washington, D.C.

Foreword

During the past 15 years, several publications on neurosurgical techniques, often with special emphasis on surgical anatomy. have appeared in the literature. Howevel; this book by J ohn L. Fox goes far beyond an ordinary effort. This extraordinary work, Allas of Neurosurgical Anat011o/: The Pte1'ional Perspective, has its or igins in the author's many years of devotion, exhaustive labors, and experience as a teacher in the operating theater (to wh ich his many residents will attest). This surgeon, born in Billings, Montana, in the ycar of 1934, authored one of his first publications as a senior resident in 1964. The tide, " Differentiation of Aneurysm from Infundibulum of the Posterior Communicating Artery," presaged his future recognition as an intracran ial aneu rysm surgeon. Now Professor Fox is known throug hout the world not only for h is many publications on su bjects in neuroscience and clinical neurosurgery, but also for his teaching methods, which utilize both television demonstrations a nd color slides of live neurosurgical anatomy in realistic depth and clarity. Such talents as a teacher have led J ohn Fox to be called forth as an instructor and lecturer in many neurosurgical seminars and courses both here and abroad, East a nd West. His presentations with color photographs showi ng true visual images now are captured with perfection in this atlas. Such photographs, with accompanying instructions and descriptions on approaches to aneurysms and tumors, have left a prominent and lasting impression on everyone who has had the opportunity to attend his lectures. This book gives us images in livin g color, images curremly unsurpassed by any other work and well illustrated as the su rgeon actually sees them. The excellent accompanying and instructive drawings help carry the reader and observer step by step through the intricacies of cisternal anatomy and pathways of intracranial surgery. This publication is divided into e ight chapters, starti ng with the history of the pterional approach in neurosurgery. The inclusion of this interesting and instructive chapter gives us an added evolutionary insight. It is co-authored by Professor Bengt Ljunggren, whose interest and expertise in neurosurgical history and aneurysm surgery are well known. Professor Ljunggren, from the University Hospital of Lund in Sweden, fascinates the reader with his accounts of the early evolution of techniques for turning the cranial fl ap. The next three chaplers by Dr. Fox carry us through in strumentation and positioning, photographic technique, and cranial anatomy. His final four chapters take us from the sylvian fissure into and thro ugh

VIII

Foreword

the carotid, chiasmatic, and inter pedu ncu lar cisterns and their en virons. Such anatomy could never be so well illustrated before the days of the operating microscope. I have followed the career of john Fox for nearly 30 years, includ ing the time since his days as a student and resident at the George Washington Un iversity Medical Cen ter through his appointment as Professor of Neurological Surgery at the same institution in Washington, D.C., on Ju ly I, 1974. Subseque nt yea rs have shown that Professor Fox not only is singularly and eminently qualified and gifted as an author of such an atlas, but also continues to have the energy and drive to give future students, anatomists, neurologists, and neu rosu rgeons such a lasting work on intracranial surgery via the pterional perspecti ve. L UDW IG

G. K EMPE, M.D.

Professor of Neurological Su rgery and Research Professor of Anatomy University of South Carolina Charleston , South Carolina

Preface

After completing a three-volume book entitled inlmcranial Aneurysms published by Springer-Verlag in 1983, this authorcomin ued to compile a set of surgical photographic slides that served well for teaching anatomy at neurosurgical rounds, meetings, and workshops. But preservation of these images for futu re sLUden ls required their publication in a more permanent form. The plerional approach to cenain imracranial problems is being used with increasing frequency, and the photographs presented here give us the plerionai, or frontolatera l, perspective - a perspective that is turned upside-down and obliqued in comparison with most standard anatomical illustrations. Yet, th is is the vlew as seen by the neurosurgeon. For ease of comparison, all photOgraphs are oriemed as if a right-sided operation is being performed. In one sense, this atlas becomes "volume 4" of Intracmnial Aneurysms. However, em phasis is on live anatomy and its variations rather than on pathology. h is for this reason that this author omitted cases with basal tumors, for such masses often distort and compress the vessels and cranial nerves beyond dear recogni tion . The earthly finality of death is mitigated by the deeds one does during his or her life. One then leaves behind the results of interaction with others. As physicians we hope to have mostly benefined our patients. Sometimes we fail. This atlas nOl only is in memory of those failures. but also is a photographic epitaph of some of those very patiems, however few in number. For the many patients who survive the neurosurgeon's hand and return home to family, the surgeon can gain more than any ephemeral fame, fonune , or feeling of "well done." The neurosurgeon, more importantly, can be both a catalyst inspiring younger surgeons to greater heights and a teacher leaving behind works upon which others can build. The author, the con tributor to the chapter on history, and the artist hope that this atlas will serve such lasting purposes. J owe a debt of gratitude to my friend and colleague Professor Bengt Ljunggren at the Departmem of Neurosurgery of the University Hospital, The University of Lund, Sweden. Begin ning with the 1889 work of the German surgeon Wilhelm Wagner. Professor Ljunggren contributes a vital perspective to the history in Chapter 1. Special credit is due to David M. Klemm , medical ill ustraLOr at the Georgetown University Medical Cemer in Washington , D.C., where I carried out part of the work on this book. He drew and labeled all the illustrations that accompany the color photographs. JOHN

L. Fox

Contents

Foreword by LUDWIG C. KEMPE. Preface . . . . . . . . .

VII

H istory of the Pterional Approach and JOHN L. Fox

BENGT LJUNCGREN

Instrumentation and Positioning

Photographic Technique . . .

Cranial Anatomy and the Cranial Flap

5 The S),lvian Fissure

6 The Carotid Cistern and Environs.

7 The Chiasmatic Cistern and Environs

123

8 The Ambient and I nterpeduncular Cisterns

165

Ind ex

20 1

1 History of the Pterional Approach BENGT LJUNGGREN

Introduction Many surgical a pproaches have been proposed in order to facilitate exposure of lesions in the skull-base region wi th a minimum of brain retraction [I, 3, 12, 15, 18, 19,24,29,32-34,37, 39, 40, 49]. The pterional a pproach [0 th e circle of Willis and its environs is routinely used by many surgeons. A pterional approach implies that a small skull flap is raised with the pterion (Creek pterion, wing [ II ]) - the craniometric point located undern eath the tcmporalis muscle and form ed by the junction of the fronta l, parietal , and te mporal bones with the g reat sphe noid wi ng bone - in the center of the base of the flap (Fig. 1.1 ). Additional drillin g down of the sphe noid ridge allows a low basal exposure along the skull base. Equipped with

Fig. 1.1. Close-u p view of left

side of dry skull with sutures between the frontal (F), parietal (P), temporal (1),

sphenoidal (S), and zygomatic (l) bones outlined by black ink.

and JOH N L. Fox

today's microsurgical instrume nts, the ne u rosu rgeon finds that the pterional approach to skull-base lesions is a more natural and easier procedure than earl ier-day operations. Yet, there is a fascinating hiSlOrica l background over the last 100 years, that form s the basis o f the present-day pterional approach. There are several pioneers who made mo numental contributions to the development of this access to deep-seated cran ial-base lesions.

Wilhelm Wagner and His Osteoplastic Method followin g studies on human cadavers for several years, Wilhelm Wagner (1848 -1900) became the first su rgeon in the world to raise a

I. HislOry of the Pterional Ap proach

bone flap (temporal in site) out of the cranial vault in a living person , kee p it attached to the overlying soft tissue (perioste um, tempora l muscle, and scalp), a nd then replace the fla p (after evacuation of a la rge epidu ral hematoma) [4, 44]. Wagner used hammer and chisel to raise the bone flap. The patient, a 27year-old man with skull-base frac tures a nd the clinical picture of increasin g intracranial pressure, underwent su rgery on the second day fol lowing a seve re head injury. He was in a poor condition p rior to the ope ratio n. Following evacuation of the hematoma, it was appa rent thal the intracranial pressure had become normalized , bUl the patient did not recove r a nd d ied 24 hou rs after surger y. At a uto psy Wagne r fou nd no signs of di st urbed nutrition in the te mporal, omega-sha ped fl ap that he had raised to allow e vacuation of the now-absent hematoma. He concluded that his osteoplastic method was an excellen t procedu re that resulted in a good ex posure of lace rations of the middle me ningeal artery in the middle cranial fossa. He also suggested that his osteoplastic method could be used to ex plore and resect other intracra nial lesions such as brain abscesses, e pile ptic scars, a nd brai n tumors [44]. Two years later (1891 ) Wagne r rightly claimed priority for the introduction of the use of the above-described , intraoperative osteoplastic bone flap to ex plore intracran ial lesions. He e mphasized that such fl aps appea red to heal quickly and withou t compl ications when attachme nt to the soft tissue was retained during surgery [45]: "The osteoplastic method of trepanation is no morc difficult or da nge r. ous than an explorative laparotomy. " In 1895 Wagner publi shed two cases of success ful evacuation of e pidural hematomas throu gh his then innovative osteoplastic procedure. In this paper [46) he again e mphasi;r.ed th e adva ntages associated with tempora ry resect ion of a large bone fl ap for cx ploration of the middle meningeal bra nches. In 1909 Ha rvey Cushing [5] described Wagne r's original procedure to explore and decompress cerebral lll mors, which otherwise proved to be inoperable, using" the usua l osteoplastic method of exploration ." He summarized [5]: '~ n osteoplastic resection, whatever tools may be e mployed , has doubtless come to be made, in the hands of all , unde r

some form of tourniquet, with the omegasha ped fl ap broken off across the thin squamous wing of the temporal bone." Wagner was a self-educated surgeon who, like his great conte mporary colleague from Berlin , Ernst von Bergman n ( 1 836 ~ 1907), had been in volved in the Fra nco- Prussion War in 1870. He devo ted his life to working in the local hospi tal of Kon igshoue, a small tow n in a mining d istrict in Upper Silesia, which in 1880 cou nted 27,600 in habitan ts. Silesia at this time was incorporated into the newly founded German Re ich. In this small place Wagner became a n absolute master surgeon, and like von Be rgmann he ex hibited a pa rticula r interest in cran ial and spina l surgery. While von Bergmann strongly objected to the use of o pening the skull with chisel a nd mallet. this was the technique superbly practiced by Wagner. T he lattcr also publ ished important contributions concerning the operative management of complicated skull fractlll"es [4 3] a nd on fracture di slocations in the cervical spine [47]. His re port on the cli nical diagnosis a nd o perative evacuation of e pidural he ma tomas is a masterpiece [46] . The same ca n be said of the remarkable volume, " Die Verletzu ngen der Wirbelsaule und des Rockenma rks" [47] whic h he published in collaboration with his colleague Stolpe r from nearby Bresla u (Wroclav). Despi te a heavy clinical dail), practice, he not only kept abreast with the surgical litera tu re of the lim e but also followed the litera tu re in general med ici ne and other related bra nches . Wagner was beloved by his patie nts, for he rad iated secu rity a nd goodness and was widely recognized in the whole of Silesia not onl y for his supreme skill but also for his vast medical knowledge and his good reo sui ts in the treatment of nonsurgical d iseases.

Crania] Saws In 1891 Professor (" professeur a la Facuitc libre") J ean Toison from Lille in France repon ed on his use of a chain saw to divide the bone between burr holes from within outward to facilitate raising of osteoplastic skull fl aps [38]. This saw could replace ha mme r and chisels previously used in o pening the cranial va ult. I n his pape r Toison paid much attention to Wagner (already in his title) as the true

de Martel's Skull Trephine and Metal Gu ide

pionee r behind the revolutionizing method of Heidelberg, Cermany, Kocher from Bern, raising cranial flaps. He described Wagne r's Swi tzerla nd , Simpson from Edinburgh, Scot" historical con tribution which he first per- land , and Sklifassowsk i from SL Petersburg, formed on a li vin g human on October 1st Russia. In his pioneer pa per Oba linski gives 1889" and continu ed [38], .. Aussi la nou vell e credit to Karl Dahlgren (1864 - 1924), a methode opCraloire inauguree par W Wagne r Swed ish pioneer who, in 1896, had designed a (de Konigshuue) qu i permetde creer une vaste new bone-cutting forceps fo r making linear ouverture a la boite ossellse du crane et de re- cuts in the skull bone and which cut from the fermer, a la fin de I'ope ration, avec de I'os, inside out [6]. With the increasing interest in J'ouvertu re rendue tcmporaire de la trepana- cranial surgery in the first decade of this cention, constilUe-t-ci le un grand progres chirur- tury. the Cigli saw later became recognized also gical. Ce chirurgie n a donne a celle methode in the United States by Harvey Cushing, who operatoire Ie nOIll de rcseClion temporaire du adopted the use of this simplc instrument to dicrane . ., vide the skull bone betwee n two burr holes Toison's saw was fairl y cl umsy and was there- [36]. fore not much used [48]. T hree years later (1894) Leonardo Gigli from Florence, Italy, dede Martel's Skull Trephine and scribed his simple yet clever instrumem, a wire saw to divide bone between two open ings, This Metal Guide tool has come to bea r his name, being called the Gigli saw [ 16, 17). Origina lly, Gigli imemed his In 1908 Count Thierry de Manel (1875- 1940) wire saw to facilit.Âˇue sym physiotomy in obstetri- presented lhe perfect solution to the rest of the cal surgery. He fini shed his origi nal re port {16], problem of trephinin g wi thout risk of producemphasizing that one dozen saws could be or- in g intracranial damage. As a bo)' de Martel dered from the Hermann HarLel Compa ny in was alread y very inquisitive and enjoyed taking Breslau at the price of 3 German marks plus mechanical things apart to learn how the), op40 pfe nnig for shipping com to an)' forei gn erated [31]. Frequently he dissected the fowl country. He also added that chiefs of clinics being pre pared in the kitchen, and he bought could obta in free samples by just sending in a a skeleton that he displayed as an amiable comrequest. pan ion, de Martel, a dcscenda nt of the Professor Alfred Obalinski from the Jagicl- Mirabeau fa mil)' who played an olltstanding Ionian University of Cracow in Galicia (the role in the French Revolution, was an aristocrat haven of Polish culturc at the time, although fully conscious of his ancestry. At fi rst he was under the government of Vienna) had in- enrolled in a school for the training of entended to describe the use of the Gigli saw for gi neers and later was trained by several French cranial trepanations at the Imernational Con- master surgeons . He beca me especially ingress in Moscow in August 1897. However, he terested in neurosurgical instrumentation . At was prevemed from going and instead pub- the age of 33 he published an article [28] delished his innovative a pplication in the Cen- scri bing two new neurosu rgical instruments. tro/blatt [il r Chimrgie that same ),ea r [30]. In his Today, 80 ),ears later, both are in dail y use by paper Obalinski stated that it had occurred to many thousands of neurosurgeons all over the him that by using a slightly bcnded cannu la as world. In his milestone paper the two instruan inserter, the fl ex ible Gigli saw was ideal for ments he described were (a) a motor-driven introduction between burr holes. He em- tre phine equipped with an automatic disenphasized that the use o f the Gigli saw permits gaging gear that stopped the trephine as soon the safest method of dividing the skull bone as it has penetrated the skull and (b) the metal from the inside to the outside without th e type gu ide for the introduClion of the Gigli saw beof trauma usually seen from the use o f ham- tween separate burr holes. mer and chisel [30]. In Moscow, Emile Doyen When in Paris, de Martel presented his new from Paris demonstrated his own method for automatic trephine, but it was received with deperforming a cra niectomy in front of many rision. He then performed a demonstration prominent professors of surger)" including lI sing a dried skull with a balloon 0 11 the inside von Bergmann fro m Berli n, Czerny from as an im itaLion of the dura mater. With his au-

I. History of the Pterional Approach

Fig. 1.2. The " hypop hyseal 0' a pproach of Heuer and Dand y. From Dandy WE (1936) The braill , in Lewis D (cd): WF Prior, P roc/ice of SUrgfly, vol 12.

[71 .

LOmatic trephine he drilled a hole in this sk ull without puncturing the balloon a nd commented [31 ], "Well, as yo u call see, this treph ine can be operated by a n imbecile" ("ct bien comme valis voycz, Messieurs, cc trepan pellt manie meme par un imbecile"). American neurosurgeons were even more reluctant to accept de Mart.e1's e lectric dri ll. By the late 1930$ it was used routinely in Sca ndinavia, France, Germany, a nd Central Europe. Yet in Boston in 1948 its lise was rejected even at the Massachuseus General Hospital. The burr holes were done ma nuall y (and laboriously!) with Hudson drills. It was said that electric drills were not used because Cushing had once stated that such drills caused too much vibration transmitted to the brain (Bakay L, personal communication, 1974).

de Martel a lso had designed a hemostatic forceps, a self-reta ining cerebral retractor, and a specia l surgical chair supporting the patient for operatin g on posterior fossa tumors with the patient in the siuing position. He was the pioneer neurosurgeon in France who fou ght a nd overcame the difficulties of blood loss and inadequate posterior Fossa visualization common to neurosu r ger y during the first qua rter of this centu ry. He had lost his only son in World War I. In 1938, at the Annual Cong ress of the De utsche Gesellschaft fUr Chirurgie. de Martel gave an impassioned speech about the necessity of continued friend ship between French and German su rgeons, a speech that was followed by thunderous applause. Two years later, on Ju ne 14, 1940, as Hitler's troops occupied Paris, de Martel commited suicide [31].

Hagerstown, Maryland, pp 145, 583-585. Reprinted with permission of Practice of Surgery Ltd .

From a "Hypophyseal" to a More Pterional Approach

Fig. 1.3. Another view of the "concealed incision" (behind the hairline) of Heuer and Dandy. From Dand y WE (1936) The brain, in Lewis D (ed): WF

Prior, Practice of Surgery, \'01 12. Hagerstown, MaryÂˇ land, pp \45.583-585. Reprinted with permission of Practice of Surgery Ltd . [7].

From a .. H ypophyseaJ" to a More Pterional Approach

In 1962 George "{ayes, one of Dandy'S stud ents and former chief of neurosurgery at The Walter Reed Army Medical Center 111 Washington, D.C., briefly illustrated his frontotemporal approach in a publication with Slocum [20]. One of their figures showed " ... the visualization of an aneurysm of the anterior communicating artery as exposed through a small Dandy pituitary lype o f flap. " Hayes and his colleagues commonly used this approach to the base of the brain (Hayes GJ , personal com munication, 1974). In 1963, before the period of microneurosurgery, Lougheed and co-workers [27] stated that their operative procedure was carÂˇ ried out "through a fronto temporal bone flap

In 1918 Waller Dandy took the liberty to report for George Heuer, one of his younger colleagues, on a " hypophyseal" a pproach to pituitary tumo rs [23]. Heuer later described this approach in more detail and used it for selIaI' and suprasellar LUmors [21, 22]. In the 1940s Dandy made some modifications [7 - 10] and this lype of cranial opening became popularly known in the United States as the " Dandy nap " (Figs. 1.2-1.4). This hypophyseal approach used a skin incision concealed behind the hairline.

L History of the Plerional Approach

OpenonS .r.Âˇchnldl ~r ,

betw~~

optic n. ad

GJrotid L

Fig. 1.4. Dandy's approach to an intracranial aneurysm. Fro m Dandy WE (1944 , reprilHcd 1969) Intracranial Arterial Aneurysms. New York, Hafner.

Ski n irn:: i$ion

Fig. 1.5. The ptcrional craniotOmy flap as o utlined by Kempe. From Kempe LG [25] .

)mal\cr Copyright ]944 by Comstock Publishing Company, Inc. Re printed by permission of Cornell University Press [9].

with removal o f the pterion and a bit of the outer third of the lesser wing ohhe sphenoid. " Ludwig Kempe. who succeeded Hayes at T he Walter Reed Army Medical Ce nter, Ilicely illustrated various features of the plcrional approach (Fig. 1.5) in his 1968 two-volume alias, OPerative Neurosurgery [25] . Of interest is the description given to the critical burr hole placed at the junction of the temporal line, the zygoma tic process of the frontal bone, and the orbital ridge. At The Walter Reed Army Hospital this became known as the " psychopathic poi m " [14, 26, 4 1], probabl y in reference to the disposition of the surgeon should the residem fail to place the burr hole correctly! Subseque mly Fox learned the pterionaltcchnique of cran ial ope ning [ 13, 14] by observing or assisting George Hayes, Lud wig Kempe, and Hugo Rizzoli , Dand y'S last neurosurgical reside m o Barnes Woodhall, a nother of Da ndy'S trainees, simila r! y used the pte rional a pproach at Duke University (Woodhall B, personal communicatio n, 1980). With the imroduction of microncurosurg ical techniques, Gazi Ya~argil illustrated his

Bibliography Fig. 1.6. Diagram of skull with area usually included in a pterional flap although modified by various surgeons. From Fox JL [14].

microtechnical pterional approach [51, 54], which was a refinement of his 1969 frontotemporal descri ption [50]. He emphasized the sma ll , low basal expos ure by drilling down the sphenoid bone. At that time the basic difference between his published description and that of Ke mpe's [25] was the use of microtechnique, sphenoid bone dri lling, a wider opening of the sylvian fi ssu re, the placement of the posterior burr holes more a nteriorly (making it a frolHos phenoidal craniotomy), a nd the avoidance of retraction on the temporallobe [54]. Ya~argil and co-workers used the pterional approach for lesions in the interpeduncular cistern [52], in which situation the posterior clinoid process is a landmark that, on occasion, may hinder a clear ex posure [35]. The skin incision likewise has changed with the needs and preference ofth e individual surgeon. Dand y's original incision is illustrated in Figs. 1. 2 through 1.4. Kempe's incision (Fig. 1.5) permitted greater exposure of the temporalis mu scle as well as a more basal exposure . Various surgeons at times extend the fronta l limb a shon distance into the skin of the forehead above the junction of the medial twO thirds and lateral one third of the eyebrow. This might permit a shorter scal p incision, but itdid make part of the surgical sca r visible after hair regrowth . Ya~arg il 's incision was longer but re ma ined concealed beh ind the hairli ne while descending low enough to perm it a lower, basal a pproach [53, 54]. The pterional approaches at times can inju re the fromalis

branches of the facial nerve, a point of recent discussion [2, 55]. Throughout the years neurological surgeons have altered and modified the a pproach to the middle fossa and sellar region. In one form or anOlher the pterion has been incorporated within the reflected bone fl ap in modifications of the "pterional fl a p " (Fig. 1.6). Its evolution from the Heuer-Dand y flap to the Hayes- Kempe flap posteriorly and basally and then to the Yaprgi l nap a nteriorl y a nd basall y has been accompanied by parallel advances in imaging, anesthesia, magn ification, lighting, retraction, instrumentation, and intraoperative e nergy transfer (by laser, ultrasound, electrocautery, and the like). The pterional approach is now finding its place as an important surgical route to t he circle of Wi llis and itsenvirons. T he pioneers who laid the fund amental cornerstones to this procedure include Wilhe lm Wagner, Leonardo Gigli, Alfred Obali nski, Thierry de Martel , George He uer, and Walter Dand y. T hese are the men of years long past to be r emembered by all ne urosurgeons who today regard the pterional approach to the skull base as a n elementary and most obvious and fund a me ntal principle.

Bibliography 1. AI-Mefty 0 (1987) Supraorbital-ptcrional approach to skull base Icsions. Neurosurgery 21: 474-477

2. Aoki N (1987) Incision offacial nerve bra nch al

I. History of the Plerionai Approach

aneurysm surgery. (Leuer to the Editor) J Neurosurg 66: 482 3. Brock M, Dietz H (1978) The small frontolateral approach for the microsurgical treatment of intracranial aneurysms. Neu rochirurgia (Stultg) 21: 185- 191 4. Buchfeldcr M, Lju nggren B (1988) Wilhelm Wagner (1848- 1900). Surg Neural, in press 5. Cushing H (1909) A method of combiningexploratio n and decompression for cerebral tumors which prove to be inoperable. Surg Gynecol Obstet 9: 1-5 6. Dahlgren K (1896) Ein neues Trepanationsinstrument. Centralbl Chir 23: 217 -220 7. Dandy ,-\,IE (\936) The brain, in Lewis 0 (ed): PracliceofSurgery, Hagerstown, Md, WI<- Prior, vot 12, pp 145,583-585 8. Dandy WE ( 1938) Intracranial ane urysm of internal carotid artery. Cured by operation. An n Surg 107:654-659 9. Dandy WE (1944, reprimed 1969) Intracranial ArterialAneurysms. New York, Hafner 10. Dandy WE (1945) Intracranial arterial aneurysms, in: The Brain. New York, Harper & Row (Reprinted 1969 from WF Prior, Lewis Practice o/Surgery, Hagerstown, Md) II. Dorland's Illustrated Medical Dictionmy (1974) cd 25. Philadelphia, WB Saunders Co, p 1284 12. Dotl NM (1933) Intracranial aneurysms: cerebral arterio-radiography: surgical treatment. Edinb Med J 40: 219-234 13. Fox JL (1979) Microsurgical exposurc of intracran ial ancurysms. J Microsurg I: 2-31 14. "oX JL (1983) Intracranial Aneurysms. Ncw York, Springer-Verlag 15. Frazie r CH (1913) An approach to the hypophysis through the anterior cranial fossa. AnnSurg57: 145-150 16. Gigli L (1894) Ober ein neues Instrument wm Durchtrenncn dcr Knochen, die Drahtsage. Centralbl Chir 21: 409-411 17. Gigli L (1897) Z UI" praktischen Vcrwertung der Drahtsage. Cemralbl Chir 24: 785-788 18. Hakuba A, Liu S, Nish imura S (1986) The orbitozygomatic infratcmporal approach: A new surgical technique. Surg Neurol 26: 27 1-276 19. Harris P, Udvarhelyi GB (1957) Aneurysms arising at the internal carotid-postcrior communicating artery junction. J Neurosurg 14: 180- 19 1 20. Hares GJ , Slocum HC (1962) The achievement of optimal brain relaxation by hypervemilation technics of anesthesia.] Neurosurg 19: 65-69 21. Heuer GJ (1920) Surgical experiences with an intracrall ial approach to chiasmallesions. Arch Surg I: 368-381 22. Heuer G] (193 1) The surgical approach and treatment of tumors and other lesions about the optic chiasm. Surg Gynecol Obstet53: 489-5 18

23. Heuer C] , Dand y WE (1918) A new hypophysis operation. ] o hns HopkillS Hosp Bu ll 29: 154 24. Jane JA, Park TS, Pobereskin LH et al (1982) T he supraorbital approach: Technical note. Neurosurgery 11:537-542 25. Kempe LG (1968) Operative Neurosurgery, wl/. Cranial, Cerebral, and Intracm71ial Vascular Disease. Berlin, Springer-Verlag 26. Kcmpe LG, VanderArk GO (197 1) Anteriorcommunicating artery aneurysms. Gyrus rectus approach. Neurochirurgia (Stultg) 14: 63-70 27. Lougheed WM. BOltereH EH, r..lo rley TP (1963) Results of the direct attack in the surgical management of internal carotid and midd le cerebral aneurysms. Clin Neurosurg9: 193-200 28. de Martel T (1908) Un point de technique operaLOire dans la craniectomie. Presse Med 16:641-643 29. McArthur LL (1912) An aseptic surgical access to the pituitary body and its neighborhood. J AMA 58:2009-2011 30.0balinski A (1897) Zur Technik del' Schadeltrepanation. Centralbl Chir 24: 857-859 31. Pecker ] (1980) T hierry de Martel, 1875-1940. Surg Neurol 13: 40 1-403 32. PiteHi SO, Almeida GGM, Nakagawa EJ etal (1986) Basilar aneurysm surgery. The subtemporal approach with section of the zygomatic arch. Neurosurger y 18: 125- 128 33. Pool] L (196 1) Aneurysms of the anterior communicating artery. Bifrontal cranioLOmy and routine use of temporary dips. ] Neurosurg 18:98-112 34. Pool ] L (1962) T iming and techniques in the intracranial surgery of ruptured aneurysms of the anterior communicating artery.] Neurosurg 19: 378-388 35. Samson OS, Hodosh RM, Clark WK (1978) Microsurgical evaluation of the ptcr ional approach to aneur ysms of the distal basilar circulation. Neurosurgery 3: 135- 141 36. Seeger W (1973) Allgemeine neurochirurgische Operations tech nik, in Sailer FX, Gierhake FW (cds): Chirurgie histQrisch gesehen. Deisenhofen bei t.H.inchen, Dustri Verlag: pp 237 -238 37. Sugita K (1985) MiC1"01liurosurgical Atlas. Berlin, Spri nger-Verlag 38. Toison] (189 1) De la trepanation du crane par resection temporaire d'un lambeau osteoplastique (procede de Wagner et procede personnel). Cong Fr Chir 5: 325-338 39. Tonnis W (1936) Erfolgreiche Behandlungeines Aneurysma der Art. commun. ant. cerebri. Zentralbl Neurochir I: 39-42 40. Tonnis W, Walter W (1960) Ein neuer operativer Zugang zu den sackrormigen Aneurysmen der basalen Hirngef.isse. Wien med Wochellschr 110: 145-147 41. VanderArk CD, Kempe LG, Smith DR (1974) An-

Bibliography terior communicating aneurysms: the gyrus rectus approach. Clin Neurosurg 21: 120 - 133 42. Wagner W (1885) Uber Halswirbellu xationen. Ard,iv fur klinische Chirurgie. Berlin, Verlag von August Hirschwald , pp 192-2 16 43. Wagner W (1886) Die Behandlung der komplicirten Schadelfrakturen . Centralbl Chir 26: 2405-2510 44. Wagner W (1889) Die temporare Resektion des Schadeldaches an Stelle der Trepanation. Ein Vorschlag. Celllralbi Chir 16: 833-838 45. Wagner W (1891 ) Zwei Faile von temporarer Schadelresektion. Ccmralbl Chir 18: 25 - 29 46. Wagner W (1895) Zwei Faile von HaematOm der Dura mater geheilt durch temporare Schadelresektion. Berl klin \-I/ochenschr32 (7) : 13i - 140 47. Wagner W, Stolper P (1898) Die Verletzungen der Wirbelsaule und des Riickenmarks, in von Bergmann E, von Bruns P (eds): DeutscM Chirurgie, No 40, Stuttgart, Verlag von Ferdinand Enke, pp 1-564 48. Walkcr EA (1951) A His/ory of Neu.rological Su.rgery. Baltimore, Williams & Wilkins Co, p 50

49. Wolff J (1863) Die Osteoplasti k in ihren Bezieh ungen zur Chirurgie und Physiologic. Arch klin Chir 4: 183-294 50. Ya~argil MG (1969) Microsurgery Applied 10 Neurosurgery. Stuttgart, G Thieme, pp 119- 143 51. Ya~a rgi1 MG (1984) Microneurosurgery. Stuttgart, GThieme 52. Ya~argil MG, Antic J , Laciga R et a1 (1976) Microsurgical pterional approach to aneurysms of the basilar bifuf(:ation. Surg Neurol6: 83-91 53. Ya~argil MG, FoxJL(1975)The microsurgical approach to intracranial aneurysms. Surg Neurol 3:7-14 54. Ya~argi l MG, FoxJL, Ray MW (1975) The operative approach to aneurysms of the anterior communicating artcry, in Krayenbiihl H (cd): Advances and Technical Standards in Neurosurgery. Vienna-New York, Springer-Verlag, pp 11 3- 170 55. Yaprgil MG, Re ichman MV, Kubik S (1987) Preservation of the frontotemporal branch ofthe facial nerve using the inter fasc ialtcmporalis nap for pterional craniotOmy. Technical article. J Neurosurg 67: 463-466

-- 2 Instrumentation and Positioning

Introduction This chapter describes the surgical instrumenlS and equipment uti lized by the author during the plcrional approach to intracranial lesions. Since part of the instrumentation is used to maintain the proper position and alignment of the patient, positioning is an intimately related subj ect. The Japanese samumi was a dedicated and courageous warrior skilled in battle. He and hi s sword or bow-and-arrow were a si ngle fighting unit. They were such an integral pan of each other that activation of cerebral and muscle memory effected ra pid and nearly subconscious communication, resu lting in precise, "computerized" delivery of the weapon upon its targeted foe. The above simile is meant to emphasize the conceptual and real changes occurring in the modern ne urosurgical operating room. The neurosurgeon (samurai), the instrumentation (bow-and-a rrow), and the patient's lesion (foe) are no lon ger separate en tities. Through extensive laboratory and clinical training, unlearning old habits, and learning new methods of hand-brain-eye coordination , the modern neurosurgeon now develops cerebral and muscle memory a kin to that of the samurai . The operating microscope and microsu rgical instrume nts become an in tegral part of the surgeon who must deftly deliver his therapeutic arrow on target. If this is to be done with minimal disturbance to the patient's brain, the arrow's trajectory is limited to narrow pathways between cran ial and intracranial structures. It now ca n be appreciated that, in addition to being able to work in small, optically magnified

spaces with delicate and long dissecting instruments, thc position of the neurosurgical patient nowadays is critical to the "stereotaxic" alignment of the su rgeon's eye, the microscope, the dissecting instruments, and the ta rgeted lesion. The surgeon must supervise the positioning of the patient so that when the target is reached later in the day, the surgeon is comfonably situated for delicate dissection of the tumor or vascular anomaly within very narrow spaces. As the patienland instrumentation are being set up, the surgeon reviews a mental check list(much as an airplane pilot does) based on past experience and endeavors to control interlocking events with in the operating room. Inexact patient posi tioning or imperfect alignment of the patient's head in the historical past could be compensated by more brain retraction or by rotation of the patient's head resting on a cranial "donut." Nei ther is acceptable in most modern-day microneurosurgical procedures where the patient'S cranium is immobilized by a skull-fixation apparatus and the brain is supported by self-retaining retractors usually attached to the operating table. Thus, an incorrect pos itioning of the skull-fixation a ppa ratus, for ex.ample, may cause part of th is a pparatus to intcrfer with later placeme nt of a smail , self-retaining retractor 0 11 the in ternal carotid artery and thereby hinder the surgeon's line-of-sight to the interpeduncu lar cistern . It is in this context that "interlocking events" must be well thought out and controlled. Because the neurosurgeon is working within very narrow confines, it is even more incumbent upon the surgeon not on ly to have a thorough knowledge of normal and aberrant

2.lnstrumemation and Positioning

Fig. 2.1. A. Top of skull with burr hote at right coronal sutu re and small hole (arrow) just behi nd burr hole. B. View with camera lens at burr hole. Anterior clinoid processes (triangles), posterior clinoid processes, and left foramen ovale (wroed arrow) are ,",'ell seen at skull base. Small arrow lies on right posterior clinoid processand poims toward metal pin projecting up\\'ard from noorof sella turcica. C. Similar but morc restricted view with camera lens at smaller cranial hole (behind burr hole in A). Arrow crosses left petrous pyramid and intracranial opening o f carotid canal and poinL~ LO the foramen ovale. Figures 8 and Care rotated 90 0 counter clockwise compared with A.

Head Holder neuroanatomy but also to be able to conceptualize the anatomy in its three dimensions (stereoimage concept). The tomographic planes of computed tomography (CT) and magnetic resonance imaging (MR I) detract from such conceptua lization (whereas stereoscopic images and pneumoencephalography [45J encourages it). The medical student lea rns his anatomy from sta ndard cadaver dissections a nd textbooks. The surgeon, at least in the pterional approach illu strated in this atlas, must view the patient's anatomy from an oblique a nd upside down oriemation (wi th respect to the patient). Cranial openin gs have become smaller as microsurgical techniques have advanced. In theory, an intracranial lesion could be operated on via a tiny (eg, I mill) cranial opening (Fig. 2.1). In a sense, the operating microscope brings the surgeon's eye closer to the cran ial opening. If the surgeon's eye were at the ope ning like peering through a keyhole, a full view of the intracranial spaces could be seen - if retractors cou ld fit through the opening - and the lesion cou ld be removed or corrected - if dissectOrs, like a laser beam, could fit through the opening. Thus, among the factors limiting the use of very small cranial openings in most cranial operations are intracranial instrumentation and maneuverability. Instrumentation continues to change, depending on surgical needs. There are va riations among specific types of instruments (eg, retractor systems, cranial-fixation systems, operating tables) , and an individual surgeon often uses the system that he was trained in or that fits his particular approach. T he instruments and equipmem herein described have been the author's personal preference for the pterional approach to various intracranial lesions. Much of the following is reproduced from a previous publication [16].

External Instrumentation Operating Room Table We place the patient on the American Sterilizer operating room (OR) table so that the patient'S head is at the foot end of the table (Fig. 2.2). This has several advantages: (a) the table pedals are not in the way of the sitting surgeon's feet (the anesthesiOlogist or circulating nurse manipulates these as needed); (b) there is more

room for the base of the microscope (which we position to the left of the surgeon) ; (c) the normal opening in the OR table lies under the lumbar region of the patient's back, facilitating lumbar cerebral spinal fluid (CSF) drainage without turning the patient. The only disadvantage of this alignment is that the main weight of the patient is off the center of gravity for the OR table. An assistant often must assist in elevation of the surgeon's end of the table by lifting lip the table under the patient's shoulders when the patient'S head is raised (table fl exed) to its final position (aboma 10- to 15-degree elevation of the patient'S head). This aclion lightens the unbalanced load on the table wh ile the table is flexed. One must becareful to avoid sliding the bUllocks into the opening, which would risk sciatic nerve pressu re in short patients.

Head Holder In this era of minosurgical technique and selfretaining retractors, it usually is essential that the head be immobilized by three-poim skull fixation. We use the Mayfield-Kees skull clamp (Kees Surgical Specialty Company). T his clamp (Fig. 2.3) is inserted into the normal foot end of the American Sterilizer table. The horizontal part of the head holder should be nearly parallel wi th the fl oor. We prefer to have the two-point side of the clamp on the side of the surgery, as the opposite one-point side may project Out tOO fal: All joints are tightened securely (from above downward), a nd the head is immobilized throughout the operation. A study group sta ted (17): Under the surgical microscope, the slightest movement of the patient's head is magnified considerably. Microsurgery demands a precisely maintained position of the firmly fixed cranium throughout the entire opel'ation, whether one opcrates with the patient in the sitting. supine, or prone position. This is beSt achieved by a pillion head holder in which the essclllial clemem is a clamp made to accommodate three relatively sharp pins. The pins penetrate the scal p and are then firmly fixed to the outer (able of the skull. \Vhen placing the pins, the surgeoll shou ld take care to avoid a spinal fluid shunt, surface vessels, thin bone (such as over the frontal and mastoid sinuses), and the thick temporal muscle where the position of the pin tends to remain unstable, however tightly the clamp is applied. A pin on the forehcad should , of course, be well away from the eyc; and when the clamp is positioned too close to

2. Instrumentation and Positioning

A "

fig. 2.3. A. Mayfield-Kees head holder with demonstration skull (bone flap re moved) in position for rig ht fron(Oiatcrai craniotomy. 8 . Pa tient in position

with head turned 40° to left, tilted 15° to left. and d ro pped back 15°, From Fox [16].

~~------------------------------------------------------

Fig. 2.2. A. Sketch of American Sterilizer OR table. The usual head end is to the observer's lefl. The head rest has been rCII1O\'cd from this end and

placed at the normal foot e nd on the observer's right. T he patient'S head initially rests on the head rest on the observer's righ t with that end c!evated 10°_ 15° and with the lu mbar region oflh e patient's back res ting Mer the open ing (arrow) in the table. B. Same after specially mad e maltress is in place with opening for lumbar CS F drainage. A model skull (see Fig. 2.3) is held by the skull damp (replaci ng the head res t). An "ether screen" (bar with knob projecting toward observer) p rojects away from the le ft sid c of the paticlll to late r ho ld the d ra pes alld suction

tubes. The Leyla self- retaini ng retractor bar (see Fig. 2. 11 ) atl<lchcs (aITow) to the O R table just cephalad to the ether screen attach me nt. The microscope stands JUS t cephalad to lhe ether screen , and the anest hesiologist is positio ned caudal LO lhe et he r screen. C. Preli mina ry dra ping of paticnt. Instruments are placed o n the overhead ins trume nt ta ble (Phelan Manu fact uring Corporatio n, Minnea polis). Note the steralized "C-clam ps" at each end with rubber tubing st retched between . T hese are covered after fi nal draping and prel'cnt instruments from falling offinto the a ncsthesiologist's no nsterilc field. From Fox [ 16]. 15

2. Instrumentation and Positio ning

the incision, a pinÂˇcasing can be a hinderance. Special smaller pins available for infants can also be used for patients who have thin skulls. Pa rticular attention should be given to patie nts who have had a long history of hydrocephalus. Having secured the clamp. the surgeon holds the head in the desi red position wh ile the final attach ment to the operating table is made. Man ipulation of the head holder accurately and with safety may bcdi fÂˇ ficull at first, but with experience any obstacles e ncounlcred can usually be surmounted. This

method of skull fixation avoids the pressure injuries that may occu r to the scaJp or face when the

head has been resting on rubber pads for long periods.

The time of insertion of the poinlS imo the scalp and skull is a critical period . T he head must be perfectly posiLioned accordin g to the approach used by the surgeon . Any deficiency wi ll cause defective alignment of the target, cranial opening, microsco pe, and surgeon's eyes. The alignment must be such that there will be a dear view of the aneu rysm a t the focal poim of the microscope with the surgeon in a comfortable position. Upon insertion of the

poinlS, the patient's blood pressure and intracranial pressure will rise unless he is properly anesthetized and his blood pressure is under control. The surgeon must notify the anesthesiologist before he inserlS the poims. Colley a nd Dunn (6] recomme nded local anesthesia in the scalp at the point-insertion sites.

Surgeon's Chai r Surgeons' chairs are available from various companies, eg, Storz Instrument Compa ny, Aesculap Company, Stryker Corporation, and V. Mueller Company. Ya~a rgil el al [57] reported on their special chair; we have found the rece nt modification sold by the Aescu lap Company to be qu ite satisfactory. \Ve also have used the pneumatic lift chair (style P390244) available from lheC.C.R. Medical Corporation of PitlSbu rgh (Fig. 2.4). A hard cushion may be placed on the seal to give the surgeon a bit more height. The stool height is adjustable by pressing on the foot bar.

Operating Microscope After years of experience with neurosurgery sa ns microscope fo llowed by microneurosurgical ex per ience in his operating room, Cha rles Drake concluded [12]: The remarkable new surgical world revealed under the operating microscope and the beautiful instruments available to work in it have und oubtedly played a m.yor role in placing the safety and scope of aneurysm su rgery \\'here they are today.

And Gazi

Ya ~argil

had advised [55]:

However, it should never be forgotten that the re is much more to microtech niquc in neurosurgery than the possession of a highly perfectcd optica l instrument. This alone is o f little value without special methods of bipolar coagulation, carefull y ad apted instru ments, and, above all, atraumatic operation techniques.

Fig. 2.4. Pneumatic lift chair (C.C. R. Medical Corporation, Pittsburgh). The dark cush ion is added for extra height. From Fox [ 16] .

In 1865 Bischo ff [4] published his work on dissections of the cranial nerves. He began wi th lou pes and later graduated to the dissecting microscope with up to 50x power. The evolution of the use of the operating microscope in surgery is detailed in other publications [9, 17, 36,4 1, 43 ,55]. In 1978 a stud y grou p concluded the follow;ng [In

Operating Microscope The use of the operating microscope and microtechnique is only one part ofthe modern trend in the surgical treatment of certain cerebrovascular problems. Coincidentally, a team of experts has evoh'cd, each of whom is specially trained to carry Out his or her wsk in this type of surgery ... Although we place major emphasis upon the microsurgical tedmi<lues, advances have occurred as well in anesthesiology, nursi ng care, radiological diagnostic methods, pharmacology, and available monitori ng systems. Certainly the jud icious use of vascular hypotension and of techniques to control intracranial pressure has helped greatly to reduce patient morbidity. Some operations would be extremely difficult if not impossible to perform without today"s sophisticated personnel ... Both reports in the recent literature and the increasing use of the microscope by neurosurgeons confirm the opin ion and experience of stud y group members that the application of the operati ng microscope and microtechnique has markedly reduced the mortality and morbidity associated with intracranial aneurysm surgery. Parallel improvements in equipment have contributed additionally to these results. The cardinal factors , however, arc the training, experience, and expertise of the operating surgeon who utilizes these new tech niques and the capabilities of his operative team. Some of the technical as pects of optics, su pports, accessories, use, care, and sterilization of the microscope and its accessories are given elsewhere [10, 14, 15, 17,3 1, 35, 37, 40, 43, 55, 57]. The Zeiss operating microscope (Carl Zeiss, Inc) is the unit most commonl y used at this time (Figs. 2.5-2.7). We have been using (he counterbalanced Zeiss-Contraves unit (Figs. 2.6 and 2.7) with electronic switches that release magnetic locks, immobilizing the microscope in any desired position [57]. Our preference has been the OPM I No. I Zeiss magn ification system rather than the zoom lens system attached to the Contraves stand . We also prefer the floor mount to the ceiling mount. In our OR the television came ra is attached to the left side of the beam spl itter, and the binocular observation lUbe or still camera is attached to the right side. The newer inclinable binocular tube (Fig. 2.8) has improved the versatility of this in strumenl. With ex perience, the counterbalanced ZeissContraves microscope and the surgeon become a single entity, working comfortably "hand-in-glove" in attacking the lesion. Normally we have one surgical assistant on the right sid e of a right-handed surgeon. Thus,

this surgeon's left hand is his first assistant and the other surgeon, in effect, is his second assistant. The counterbalanced Zeiss-Contraves microscope, first used by Ya~a rg il [57] in Zurich, can be auached to laser systems or used in conjunction with an ultrasonic aspirator. With the former, the mobile microscope comes over the left shoulder of the surgeon while the attached laser unit is off to the surgeon's direCt left and siLS between the microscope stan d and the anesthesiologist's equipment. Other excellent o perating microscope syste ms arc available. For exa mple. Kenichiro Sugita in Matsumoto, Japan, h as develo ped a highl y sophisticated system [48]. Although agreement is not universal as to whe n the microscope should be brought into the operative field, ex perience shows that a more gentle, accurate, a nd rapid dissection ca n be carried out if, once the dura is opened, the entire approach to the a ne urysm and its dissection are carried out under the microscope. With the patient supine, the angled position of the incl inable binocula r lUbe is used most often. This now can be easi ly altered to a straighte r position when drilling the sphenoid wing a nd to a sharper angle when dissection is in the sylvian fi ssure or antcrior perforated substance. With ex perience, the surgeon often finds that he routinely uses the same highe r magnification (eg, 6x or 8x true magnification) for the approach to the tumor or aneurysm as he d oes for its dissection. Several disadvantages to the o perating microscope have been mentioned [ 17]: Special tra ining is required for using the microscope. microtools. a nd microsllture; it necessitates o perating in a deep, narrow gap ; it requires longer adaptation time ; it does not permit good tissue palpation (i nstrume nts are used , not fingers) and requires visual manipulation ; work is indirect; work is tiring to the eyes; stiff neck, should ers, a nd back generall y result; distractions are poorly toleraLCd; equipme nt and training a re expensive; it lakes up space in the o perating room; and the operating time for most surgeons is longer. The advantages for the ne urosu rgeon far a outweigh any drawbacks, however [17]: Fewer parallax problems occur because the objective le ns brings the largetcloser to the surgeon's vision; binocular vision is improved; ill umination is incrcased ; the foc us is sharper; a nd magnification permits a smaller cran iotomy, less brain

2. Instrumelllation and Positioning Fig. 2.5. Standard Zeiss operating microscope with zoom lens system. f\lounted on Zeiss Universal S3B noorstand. Counesy of Carl Zeiss, Inc.

retraction, a smaller cortical incision , and better delineation of normal a nd abnormal anatomy. Structures that are beller idcmified by the microscope are the arachnoid space, compartments, and bands; the perforating arÂˇ tcries; vascular variations in the circle of Willis; aneurysmal anatomy; microaneurysms; the impending rupture of an aneurysm; small bleeding points for bipolar coagulation; and the nerves [17]. The advantages to the patienlarc a smaller wound, beller repair or nerves a nd vessels, the fact that some inoperable lesions become operable, optimal hemostasis, fewer surgicallcsions, and fewer postoperative complications [ 17 ]. Educational advantages include

use of the observer tube, television with tape recording, and cinematogra phy or still photography. I n addition, the television system allows the scrub nurse and anesthesiologist to know the state of the surgery from moment to moment. As the microsu rgical era began, Drake in 1965 stated [11]: The ability to see the minute details of the structures about an aneurysm has been, in my opinion, the source of much trouble in this as ill other fields of neurosurgery ... There is a new world waiting for us. The dissecting microscope with its superb illumination is ideal.

Operaling Microscope

fig. 2.6. A. CoUi ltcrixliallccd 7..ciss-Collt ra\cs o llCrat ing micrOKope. B. CloseÂˇup of microscope. From Fox [ 16]:courlCsy ofC:lrI Zeiss. Inc.

2. Instrumenta tion and Positioning

Fig. 2.7. A. Zeiss-Contravcs o perating microscope in position at surgery. The bone flap has been turned. Note the rubber wbi ng that holds the drapes firm ly down and caudally. Abo\'c arc two suction tubes in readiness. In the background is a telc\Âˇisio n monitor.

B. Close-u p of microscope and alLach ments. Left: Sony lclc\Âˇision camera and microphone. Cn!Ur: binocular system and beam-spiller. RighI: assistant's observation tube. The lauer is rcmo\'cd when stillcamera photographs arc made. From Fox [ 16].

Operating

~" icroscope

Fig. 2.8. Inclinable billoclliartube (Carl Zeiss. Inc) flanked by SonyT V camerit on left and Contax still camera on right. A. In straight positiull . B. 111 angled positiun.

2. Instrumentation and Positioning

Gillingham cautioned , however [22]: This is a moment 1O reflect on the use of magnification. [\ may make us len times morc gentle but it leads to obsessive over dissection in an endeavor to find the neck ofa sac which is nonexistent orcxcessivc manipulation in the region oftbe neck.

Television As memioned above, television has imponant ed ucational adv3mages (live visualization of microanatomy and taping procedures for fulure teaching) as well as practical advantages [17,32]. Operating room physicians and nurses alter their anesthetic techniques a nd ongoing activities as wel l as morc efficiently prepare for anticipated operative CVClllS based on information received from the television monitor. Color television systems (see Fig. 2.7 B) for the microscope arc in a state o f rapid evolution in terms of image clarity and brighmess, weight, durability, and freedom from need for frequem repa irs. Hence, il is pointless to recommend specific systems allhis time. Many of the newer television cameras can operate at a lowe r light level. Yct it is still advantageous to obtai n good lighting to allow a smaller diaphragm ope ning and consequently a greater de pth of fie ld and sharper focus. Table 2. 1 su mmarizes some methods to improve lighting for the surgeon and for the television or pho1.Ographic cameras.

Overhead Table In our experie nce, the overhead table (sec Fig. 2.2 C) made by the Ph elan Manufacturing

Corporation (Minneapoli s) has provided maxi mum advantages for the surgeon, anesthesiologist, scrub nurse, and patien t. The cranial e nd of the table should bejustcaudal to the patien t's shoulder (more caudal if the cervical carotid a rtery needs 1.0 be exposed). The table height is easily adjusted , and the nurse or technician has clear and rapid access to in strumems a nd the su rgeon's hanet.

I ntraoperative Instrumentation Fishhooks The use of improvised tissue-retraction hooks, or "fishhooks," connected to rubber bands has

Table 2.1 . Methods of improvi ng lighti ng for the surgeon and/or camer<ts." I. I ncrease voltage in transformer (s hortcns bulb life). 2. Use an cfficiem lighting system (currently in state ofimÂˇ pnll'ement). 3. Keep hull>s and optical system clean. 4. Discard bulbs ",it h blue or dark spots in light image. 5. Usc add-on light sources. 6. Usc short focal length objecti\'e lens. 7. Avoid zoom !ens system. which absorl>s more light. 8. Turn off bright lights in opcr.lting room (bener conu'ast; surgeon's pupils arc d il'lIcn. rcrruiring less light ). 9. ~ I ake use of inlernal rencctions in surgical wound; a,-oid rencclions back in to the microscope. 10_ Remo" e black paint border aruund glass light dencctor behind objecti ve lens (present in some microscopes). II. Usc 30-70 beam splitrer (70% to side arms. onl), 30% (0 surgeon) inslead of 50-50 beam spliuer. 12. Use greater magnification in e)'cpicces. thercby requ iri n~ less rnagn.i fic3tion (hence less light loss) inside mrr.ros<;ope unll. 13. OllCn diaphragm to camera (with loss of sharpness and depth of focus). 14. l'rollCrI}, adjust TV camera power supply and TV monitor. 15. SeleCl efficient TV camera or film that can OllCrale wit h less light.

Certain mClhods listen ha\'e particular \'"Iue in some circumstances, whereas in others they may pro\'e unnecessary or impractical. Items I through 10 also increasc brightness for the surgeon . Item II decrease~ image brightness to the surgeon. From Fox et al [ 171.

been used by many surgeons to retract scalp, muscle, and du ra. More recently a fi shh ook retractor device using springs (Aesculap Instrumelll Co.) instead of rubber bands has been suggested [57]. We prefer the "disposable" Week Durahooks (Edward Week and Company), a lthoug h one can remove their rubber bands fo r repeated usc. The hooks a re used to retract the froillolemporal scalp flap tlIrned over the patient's forehead as follows (Fig. 2.9): The sterile drapes between the overhead table (neu rosurgical instrume ll t table; Phelan Manufactllring Corporation, Minneapolis) and the patient's head are -held firml y downward and caudall y by standard rubber suction tubing of appropriate length. The looped e nds of this tubing arc secured LO stirrup cla mps on each side of the OR table. This lube (a) firmly holds the drapes in place and (b) allows a convenient site of allachmem fo r the rubber bands that retract both the scalp hooks and the bone flap. I n this way the drapes of the pcrioperalive field are

Intraoperati\"e Instrumentation

Fig. 2.9. Close-up view of ru bber tube holding drapes firm ly (sec Fig. 2.7 A). Here the samc tubi ng is used to attach the rubber b..1nds hold ing thc fishhooks. T hese fis hhooks retract thc oxrccllu lose-co-. vcred scalp nap forward . The rig ht fromolateral

bonc nap is attachcd to the lcm poralis musclc (at cemcr of figure). Dural lack-up sutures and boncnap sutures are in place in the cranium before the dura is opened. From Fox [ 16].

smooth , firm , and dear of unnecessary damps and other retractors.

slruCled to allow regulation of suction strength by adjusting the degree to which the thumb occludes the ai r ho le. T hese ho lcs ca n be enlarged [5, 29]. and/or venting needles can be placed in rubber suction tubes. T he trap bottles ca n have pressure-regu lating gauges. When dissecting delicate SlnlClUres, it may be helpful to use specia l smooth-tipped suction tubes and negative pressures o f about 2 m of WaleI' (a pproximatel y 0.2 alln) [57]. I n place of wa ll sllction, some sllrgeons prefer an electric suction pump, easily regulated by adjusting the dia ls on the pum p. Irrib'<lting flu id in cunjunction with the suction apparatus is essential during the surgical proced ure. In addition to keeping tissues from drying and the aneu rysm wall from becom ing briule, it discourages the formalion of small blood clots and their.ad herence to the dissected surfaces; it also increases the effectiveness

SUClion an d SUClion- l rrigation Devices SUClion tubes usually are sized (diameter) by the "French" (Fr) designation: a 3- Fr size has an oLlterdiameter of 1 mm ; a 9- Fr size is 3 mm ; ctc. Standard sizes for aneurysm surgery are 3- Fr, 7-Fr, 9-Fr, and II -Fr, al though there are many other variations. There are a multitude of types of suction lubes with variation s in length. angulation, tip co nfi guration, and vacuum pressure [3, 5, 17,28,29,44,56, 57J. A SUClion system with a mechanism to controlthe negative pressure at ve ry low levels is essential . The suction should be finel yadjusled to eliminate the ha7...1nl of small anatomica l structures bein g entrapped and damaged. Many neurosurgica l suction tubes are con-

2. Instrumentation and Positioning

We commonl y use the Le ksell, Echlin , a nd Lempert rongc urs for frontotemporal craniolOmy, where bone is rongeured away at the base. The fl at-j awed Lempert rongeur is especiall y helpful for removing that portion of the sphenoid wing sticki ng Out as a ridge toward the sylvian fissue. The neurosurgeon needs a small , highspeed electric or pneumatic drill for removing the sphenoid ridge, the clinoid process, and other protrusions of the cranial base; however, only after he has become acquainted with a nd skilled in its application in the laboratory sho uld he use a h igh-speed drill in a neurosurgica l operation [17J . A drill that ca n reve rse its direction is pre fe rred by some to one that cuts in only one di rection . A constantsuctioll-irrigation system with physiological saline ca n be used to cool the drill ; o therwise, heat is transmitted to nearby neural structures. One obmins a more accurate a nd controlled use of the drill when it is operated at high speeds; o nly very slight pressure shou ld be used to remove the bon e. Dangero us skiddi ng may OCClll" at slow speed s or with dull drill bits because of the greater pressure needed to cut bone. When using lightweight drills or burrs, steel burrs are used when the drilling is remote from the dura. Diamond burrs are sa fer close to the du ra or vital structures, for they tend less to tea r SOfllissue. We use oxycellulose rather than cotton sponges to cover the nearby galea, muscle, and bone fl a p , as no harm occurs if these get caught in the drill. Couon , on the mher hand , may cause serious damage if caught in the drill. When using bonewax under the microBone-Removal Instruments scope, we have fo und the fo llowing to be helpIn 1930 Rogers [46] gave an excellent historica l ful: The scrub nu rse applies a small bit of account of cra niotomy methods. He noted that bonewax to one side of a small , d ry COllonoid the Horsley trephine had its origins in the time a nd hands it by bayonet forceps to the center of of Hippocrates (ca 400 years Be) . The the surgeon's operative field. The surgeon technique of bone flap removal made a signifi- then can use his bipolar forceps (without curcam ad vance with C igli's applicatio n of the rent applied ) or his finger to push the C01wi re saw (the C igli saw) in 1894 [19, 20]. This tonoid against the wax, which is pressed into saw is still routinely used by many surgeons - the bleeding bone. Usually we use this especially in elderly patients where the dura tech nique on the sphenoid wing a fter drilling may be stuck to the inner table of the skull . T he it under magnification. present-d ay use of power (pneumatic or electric) drill s a nd cran iotomy for lifting skull fl aps Electrocautery is well known and requires no further discussion here. Electrocautery for coagulation of vessels and Ro ngeu rs for biting away the base of the vascular tissues has been an in1.egral pa rt of bone flap are standard in a ny cra nio lOmy set. neurosurgery ever since the advent of the

of bipola r coagulation and reduces tissue adhesiveness. Constant bathing with CSF has the same effect. Some surgeons prefer a combination suctio n-irrigation unit. We usuall y use a n angulatcd Frazier suction tube of varyi ng lengths. The II-Fr a nd g-Ff sizes are used for cra nial work and the 7-Fr for aneurysm dissection. We use the 7- Fr size rathe r than smaller suction tubes because of its usc as a dissector and retractor as well as a suction device. Moreover, the large r diameter provides less air a nd liquid veloci ty for the same vacuum pressu re. The metal suction tube can also be used for resting microscissors or other instruments to reduce tremor when making a delicate d issection . The suction lube is held in the su rgeon's left hand , often with his ha nd or fifth finger resting on the Leyla retractor bar of the skull. (This "resting fi nger" serves more to provide proprioceptive feedback rather than comfol"( to the su rgeon. ) The SUClion is often used against small dental cotton balls (Richmond Dental Colton Company, Charlo tte, North Carol ina) or small cottonoids for suction protection and retraction. Rubber tubing is preferred to plastic tubing, the latter being too stiff for com fo rtable usc. We routinely put 1,000 units of he parin in each liter of irrigating solution 1.0 limit dotting, which could cause o bstruction within the tubing; this practice may retard undesirable d Olting in the basilar ciste rns as well. The on ly time we use a suction-irrigation apparatus (House-Radpour unit) is during bone (sphenoid wing or clinoid process) drilling.

Imr3oper.uivc Instrumentation Fig. 2. 10. Fox bipolar electrocautery forceps in three lengths: 16, 18, and 20 em. Each of the straight forceps cOl11es in 0.5- and 1.0-111111 diameter tips; curved and angled tips also are available. From Fox [ 16]; counesy of V. Mueller Compau)'. Chicago.

.. Bovie" electrosurgical un it, reponed by Cushing and Bovie in 1928 [7]. Light [38] gave a good historical ove rview of the subject in 1945. In 1967 Malis [39] reviewed the de,'elopments and evolution of bipolar cle<.:trocoagulation since thc ti me of Grcenwood in 1940 [23]. " Monopolar" elcctrocoagulation has been and continues to be commonly used to coagulate or cut tissues. (Of course, it is reall y bipolar: One pole is the "ground plate" and the other is the hand-hcld electrode.) Bi pola r electrocoagulation of the type whcre both poles arc in the forceps was developed by Grcenwood [23-26] to cauterize small blood vessels on the spinal cord , whcre minimal heat and electrical spread ,.,rere essential. Accordin gly. the bipolar force ps basically consists of a modification of ordinary bayo net forceps or jewelers' force ps in which each blade of the forceps is one of the electrodcs or poles; the blades are isolat.ed from each Other by insulation, which separates them at thei r base. For microvascular and intracran ial aneurysm surgery and ford issection of tumors fro m the bra instclll , bipolar electrocautery un its have become essential. There have been many mod ifica tions in both the fo rceps and the po"crsupply [8, 13, 18,23-27,33,34,39,47, 52.53, 56,57]. Malis [39] improved th e power supply ( 0 provid e a damped wave spark un it that was electricall y bener isolated. This un it (Cod man and Shurtleff Company) has bee n one of the more popular and reliable un its for neurosurgery (and is preferred by us). The unit was designed specificall y to provide the best coagulation at the lowest voltage with the

least muscle stimulation. At the same time, it restricts the current to the shon cst path between the tips of the twO blades of the forceps, with no currenL of consequence nowing from tip to ground or tip to patient. The greater safety of bipolar coagulation compat'ed with monopolar coagulation around brain stem structures was demonstrated by Gestring et al [ 18]. Some tried to provide a single unit for both mono polar and bipolar electrocoagulation [ 18, 27]. Sugita et al (52, 53] uscd a thermister at the tip of their forceps to aUlomaticaliy cut o rf the eleclriccurren t when a preset temperature was rcached . Oth ers developed a suction [47] or irrigation [13, 34] systcm attached to one blade of their forceps. Del ong and Fox [8] described an automalic cyclin g on-off bipolar electrocautery power supply. We used to prefer the Ya~a rgi l bipolar forcc ps [56, 57] (Mathys & Sohn, Zurich), but we now use the stai n less-steel Fox bi polar bayonet force ps (V. Mu eller Company, Chicago) (Fig. 2.10). T hesc forccps come in 16-, 18-, and 20-cm lengths and with 0.5- and I.O-mm tip diametcrs . Other popu lar bipolar forceps fo r surge ry include the Rhoton round-handled forceps and the Malis forceps with the blades slightly angled downward rather than parallel lO the hand le. Titan ium or stai nless steel are commonly used metals, the former being liglllcr. We prefer the heavier weight of the stainless-steel for ceps for bettcr balance, com fo rt, and proprioceptive feedback. It is important nOl to sterilize titanium and stain less-steel instruments in the same package, for the different. metals in close proxi mity may create an

2. Instrurnentation and Positioning

electrical potcmial conductive to rusting a nd

pOOl; resu lting in poor coagu lation and a tcnde ncy for vcssels to ex plode or be incised. ProDe Long and Fox [8} recommended the fol - longed or illlensh'C use, even in one patie nt, lowing care of t hese forceps to lim it thc slicking may res ult in a need for a n elCClrical overhaul. oftisslICS to thei r tips: Thcre fore, twO o r more such bipola r powcr supplies should be ava ilable. We use a 15-foot I. Do not short-circuit the electric curre nt by cord between the power supply and the fortouching the forceps lips together. ceps. Longer cord s may cause de fecti ve electri2. Clea n the lips frequemly only with a damp ca l o utput at the forceps. We set the power supd oth (not with the sca lpe!!) ply at the foot of the OR L:'l ble. I n this positio n 3. Polish the lips periodically (or obtain new it does not add to th e instrument cluneI' near force ps) when the tips become pitted a nd the surgeon, a nd ilS electromagnetic noise rough. emission is a suffi cie nt di stance from the televi4." Knead " the tissue between the forceps tips sion system so as to not c"eatc any significalll by gelltly squee zing and releasing the fora udiovisual in tcr ference. For the same reason, ceps blades. the wa ll socket plug-i n sites for the television 5. Lift lhe force ps from tissue contact freand the bipolar I)()\\'er supply units should be quentl y. at a considerabl e dista nce from each o ther. The 6. Kee p the tissue moist with CSF or saline. " monopolar " a nd bipolar electrocautery cords 7. Avoid high current settings. sho uld not be dose to each other. 8. Apply t he currCIll in shon bursts to allow heat dissipation.

corrosive activit),.

Wc usc the bipola r forccps as the principal d isscCling a nd tissuc-separating instrument intracranially. Fo r this reason the blades o f the fo rceps must have proper spreading tcnsion, yct not be so tense as to ma ke tip approximation uncomfortable. T hey must not rotatc inappropriately in the surgcon's hand. In terms of timc, its actual a pplication for e lectroca utcri zation is quite short compared with its use as a tissue dissector, pcrforator, spreader, separatet; a nd grasper. It is uscd to place a nd remove cotlonoids , cotton balls, gelatin sponge, gelatin paste, oxycellu lose, and I'LIbbel' or plastic sheclS. On tcrms of frequenc ), a nd duratio n of usc, for us the suction lube (in the surgeon's left hand) and the bipolar electrocautcry forceps (in the right hand) havc become thc main micros urgical inSlrulllcnlS during intracranial surgcr)', For most of o ur extracra nial cauterization we usecither the monopolarorthe bipolar unit with the Malis powcr supply dial set at 30 or 35. On cerebral cOrtcx wc use the Malis bipolar power supply d ial al the 25 to 30 seuings: on the brainstem we use the 15 to 25 settings. "iner-tipped force ps increase thc cun'ent density at the tips. If higher settin gs are required, lhe spark ga p in the unit probabl y needs resettin g. With faulty spark gap distances or other electrical proble ms, o ne ca n use hig her power settin gs to obtai n more current, but the qualit y (waveforms) of the e lectrica l OLitput will be

Retractors In past yea rs mOSt brain retraction wasdonc by assistant surgeons. Such retraction was often inconsistcnt, inaccurate, and dangerous, as brain retraction prcss urc exceeded cerebral pcrfusion pressure. In 1958 Gi llin gham [21] warned that bleedin g from an a neurysm at surgery (causing reve rsal of blood now from vital brain tissues a nd a drop in blood pressure) may result in ischem ia of nearby brain tissuc. He wa rned that thi s wou ld be aggravated by excess or prolonged brain retraction. Add itionall y, he ca utio ned that inaccurate o r excessive retraction may place traction o n vital perforators, producin g vasospasm a nd inadequate ce rebral perfu sion. Albin e t al [ I. 2, 17] havc shown that brain retraction pressures exceeding 20 I.o rr cause underlying brain damage. I f induced hypote nsio n is used, evcn Icss bra in retraction prcssUl'e is IOlerated . A number o f authors have described the use of self-rel.aining b rain retractors [17,29,30,40, 42,57], Various t)'pes, eit her in the literature or in commercial catalogs, have included the de Ma nel , Dolt (Edinburgh), Hamby, Greenberg, Ya ~a rgi l (Leyla), Dohn-Ca rton. Malis, Clowa rd , Enker, Miskimon, and J annclta retractor syste ms. Self-reta inin g retractors also have become indispensablc to aneurys m surgery because they allow th e surgeon to work in a relativel y

Other Microsurgical Instruments

confined space unhinde red by the presence of' an assistant's hands, which are less dependable for maintain ing constant retraction of the brain . Sel f-reta ining brain retractors arc of two basic types [ 17]. One is composed of a series of stra ight shafts attached by small clamps to give the co rrect arm length and con fi guration requ ired for holding the brain spatula in place. T he otherconsislS of a series of ball-and-socket un its resembling a cha in of peads with an internal cable that when tightened, remai ns in the desi red position . Of greatest impon a nce in intracranial surge ry is the minimal brain retraction necessary (Table 2.2), ascribable not on ly to use of the su rgical microscope and microtechnique bu t also to improvemenls in exposure techniq ues that allow a lowel; basal, and ta ngential approach to the base of the sk ull and the circle of Wi llis, which is partly aided by removal of a portion of the sphenoid wing and lhe use of special self-retaini ng brain retractors. However, these aids wo uld be totall y useless without a relaxed brain effected by proper timing of surgery and by supe rior anesthetic a nd lifesupport methods. T he selection of a self-retaining retraClor system is up to the ind ividual surgeon's preferellce and habit. Many prefer systems that attach on ly to the sku ll . T hey are concerned that table-mounted retractors may move relative to the brain even if the skull is immobilized by three-point fixa tion [40]. We have foun d that the Aescu l a p -Ya~argi l (Lcyla) retractor system (Fig. 2. 11) is ideal for most cases of intracran ial aneurysm surgery. We auach the bar to the left

Table 2.2. Minimal brain retraction. I'crmincd by: I. Usc of microS(ope. mi<;rotC(;hnique 2. Low oosal. tangemial approach 3. Self-retaining br.lin retractor 4. CSF drainage :1. Neumanest hetic techniques Avoids: I. Removal of significant brain for exposurc of lesion 2. CUlling of Olfactory nCf\'c 3. Dil'iding of SOIllC bridging I'eins 4. Secondary brain contusion o r edema, vascular spasm 5. Vascular compression by retractoror stretched arachnoidal bands 6. Tr.letion on aneurysm 7. UnnC(;essary exposure of AÂˇI and M-I arterial segmcl11s From Fox et al r17 1.

side of the O R table just cran ial to the "ether screen" attachmen t (wh ich holds drapes that separate the m icroscope from the anes+ thesiologist; see Fig. 2.2 B). Two or three fl exible (unless tightened) retractor ar ms are at+ tached to the con nectors on the bar. All joi nts must be firmly tightened to avoid drift. Fi rst, set the retractor blade (i n the flex ible a rm) neal" the planned retraction site. T hen tighte n the flex ible bar by turning [he screw, which pulls the internal wire taul. Last, "toein" the retractor blade to its desired position a nd retraction press ure an d then tighten its wing nut. Drift is minimal or absent if done properly. Always have the poi lll of connection between the retractor blade and flexible bar away from the cra nial opening. This requires auaching the flexible arm ncar the end of the retractor blade and bending the blade at its proper poi nt for descent into the cranial cavi ty. T his ma neuver gives better in tracranial exposure wi thout the ends of the fl exible retractor arms being in the way. Although these retractors a re usually ap plied against brai n tissue or its coverings, on occasion a narrow retractor ca n be used to gently retract nerves, aneurysms, or aneries such as the internal carotid anery or the middle cerebral artery d uring frontotemporal approaches to the interped uncular cistern [ 16, 48,50,51]. Such retraClion requires d isplacement and protection of these arteries \I'jthout occluding them.

O the r Microsu rgical Instrume nts T here are now a large number of microsurgica l instruments in the fie ld of neu rosu rgery. We ca nnot review all of them in this rapidly changi ng field . Figures 2. 12 and 2. 13 ill ustrate some of the instruments we most commonly use for microdissection. The j ewelers' fo rceps is used to pick up the arachnoid over the sylvian fiss ure to in itiate opening of this fissure. T he Aescu lap bayonet scissors (cu rved and stra ight) come in three lengths (16 cm for surface work, 18 cm for work about the anterior circle of Willis, and 20 cm for deeper work, eg, aboulthe posterior circle of Wi llis). T here is also a 22-cm scissor. The bipolar forceps have been described in the earl ier section on electrocautery. T he Rhoton

2. Instrumemation and Positioning

....

Fig. 2.11. A- D. Leyla (Ya~arÂ gil) retractor system. Courtesy of Aesculap-\'\'erke AG, TUlli ingen, \Vest Germany. B. Close-up view of auachmCIlt head between the bar (left) and retractor a rm connector (right). C. Close-u p view of connector bell,'ceo bar and OR table. D. Retractor h.1r and attachment head in prcliminaryposition.Above is the draped scalp with an outline of a righl froruolateral cran iotomy incision. From Fox [ 16] .

Olher Microsurgical Instruments

fig. 2.11

instruments shown in Fig. 2.13 are the four types most commonly used by us. The "Iong flat instrument" (a ,. micro-Penfield No.4 ") is used to retract nerves, arte ries, and the aneurysm. The "short fl at instrument" is ideal for se parating adhesions between an aneurysm and adjacent tissues because the edges of its angled, flat end are somew hat sharp. The 40Â° hook is sa fer to use than the right-angled hook, for it will not catch and tear tissues upon iLS removal fro m the field. A ball-tipped hook also is helpful. I nstruments and sutu re for reanastomosing or repairing blood vessels and nerves should be available along with the expertise to do so. These are detailed in many articles on microvascular anastomosis. These microsurgical instruments require some trai ning and ex perience in their use and manipulation through a small openi ng and insid e a deep narrow cavi ty. The su rgeon can rest

his hand on the skull oron the Leyla retractor bar (named after the daughter of Ya~argil) , which holds the self-retain ing retractors. Often the surgeon rests only his fifth finger as a point of proprioceptive feedback. This allows sensory orientation a nd reduces tremor. One instrument can also be rested on the suction tube of the surgeon's left hand to red uce tremor in critical moments. On occasion a mirror a t the tip of a probe can be useful for seei ng behind and around va riou s structu res . Wilson and Spelzler 154] used a denta l mirmr, Sugi ta et al [49] a 5-mm mirror, and Ya~argil and colleagues [57J a mirror that changes positions when the grip handle is squeezed. There now are many types, sizes, and configurations of vascu lar and aneurysm dips a nd clip-appliers. These are in a continual state of evol Ulion, a nd lhe reader is referred to other articles on the subject [14, 16]. T he technology

2. Instrume ntation and Positio ning

fi g. 2.13. Enlarged view of microsurgical dissecti ng instruments (Rhoton ty pe: V. Mueller Company). Ltft nld: No . 7, or "Iong n at instrument." ufl u1!l~r: No.2, o r "short n at instrument," RigJllullter: No. II , or " 400 hook." Righi tl,d: No. 10, o r "right angle hook." From Fox l I6].

fig. 2.12. uft: J c\\'clc l's' forceps (Ed ward Week & Co.). C~lIlf'r; Bayonet sha ped microscissors (Aesculap Instrume nts). Rig"': Ua),oncI shaped bipola r electrocautery forceps (Math)'s & Soho). From Fox 116].

of e ne rgy tran sfer (lase r, ultrasound) in the ope rating room is a large and changing field that will not be addressed here.

Bibliograp hy I. Albi n MS, Buncgin L, Be n nclt MH et 31 (19i7) Clin ical and experimemal brai n retraction pres-

sure monito ring. Acta Ncurol Scand (supp! 64) 56: 522-523

2. Albin MS, Bunegin L. DltiOVIlY M et al ( 1975) Brain retraction preSS urC during intracranial procedu rcs. Surg ,"brum 26: 499 - 500 3. ll.1dcr DC H ( 1975) ~'I icro-su rgical treatment of intracranial ancurys ms. J Neu ros urg Nu rs 7:25 - 27 4. Bischoff EPE ( 1865) Mikrru1wJ!~ht Analyst der ArwstomoStn der Kopfr!trotrl. Munich , Vcrlag der JJ Lentnc r'sche n Buch handlung. See 'Hicroscopic Arw{ysis of tht Allas/olllos;s Up/weer! /IU! emllia{ Nerves, translated by Sachs EJr, Va ltin ÂŁW ( 1977) Hanover, N H , Un i\'ersity Press o r New England 5. Bo ndu ra nt C P ( 1977) Alte ration or suctio n lip prcssure. J Neuros u rg 46: 559 6. Colley PS, Du n n RC J r (1979) Pre\'ention o r blood pressu re respo nsc 10 sku ll-pin head holder by local anesthesia. Anesth Analg (Cle\'e) 58:241-243 7. Cushing H , BO" ie WT ( 1928) Electro-su rgery as ,III aid to the rc moval or im rac ra nial tu mors. Su rg G}'llccol Obstel 4 7: 751- 784

Bibliography 8. De long \V B, Fo x J L (1977) Automatic q-cling bipola rcoagulator. Surg Neurol8: 15- 16 9. Donaghy Rfo.·IP (1979) The history of microsurgery in neurosurgery. Cli n Neurosurg 26:619-625 10. Donaghy R t\.H~ Ya~argil MG (1967) MicrQ-WSWlar Surge/yo Stungart, G T hieme II. Drake CG (1965) On the surgical treatment of ruptured intracranial aneurysms. Cl in Neurosurg 13: 122 - 155 12. Drake CG (l976) Ccrcbral aneurysm surgeryan uJXIatc, in Scheinberg P (cd): Cerebrqvascular Disease. Tenth Prineeton Conference. New ' ork, Ral'en Press, pp 289 - 3 10 13. Dujovny M, Vas R, Osgood CP et al (1975) Automatically irrigated bipolar forceps. Tech nical note. J Neurosurg 43: 502-503 14 . Fox J L(1976) Va~cularclips fort he microsurgical (reat melll of stroke. Stroke 7: 489-500 15. Fox J L (1979) Miu osurgical cxposure of intracranial aneurysms. J Microsurg I: 2- 31 16. Fox J L (1983) Intracranial Aneurysms. New York, Springer-Verlag, pp 678 - 707 17. Fox .I L, Albin MS, Bader DCH et a1(1978) Microsurgical treatme nt of neurovascular d isease. Neurosurgery 3: 285-337 18. Gestri ng FG, Koos WT , Boeck FW (1972) Bipo la r coagulation with modified cOtl\'emional electrocoagulators. Technical note . .I Nellrosurg 37:50 1- 504 19. Gigli L (1894) Ober ein neues Instrument zum Du rchtrcnnen der Knochen, die Drahtsage. Centralbl ChiI' 21: 409 - 4 11 20. Gigli L (1898) Zur Technik der temporaren Schadelresektion mit meiner Drahtsiige. Celltralbl Chir 25: 425 - 428 21. Gill ingham fJ (1958) The management of ru ptured intracranial aneurysm. Ann R Coli Surg 23:89-1 17 22. Gi llingham FJ (1976) Twent)'-five yea r~' experience with midd lc ccrcbral aneurysms. Rev Ins[ Nac Ncurol (Mcx) 10; 16-21 23. Greenwood J J r (1940) 1\\'0 point coagu lation. A new principle a nd instru ment for applying coagulation current in ncurosurgery. Am J Surg 50:267-270 24. Grecnwood .I JI" (1942) 1\\'0 point coagulation. A fo llow-u p report on a new techni<llIe and instrument for electrocoagulation in neurosurgcry. Arch Phys T her 23: 552 - 554 25. Greenwood J J r (1955) Two-point or interpola r coagulation. Review after a twelve-}'car period with !lotcs on add ition of sucker tip. J Neul"Osurg 12: 196- 197 26. Greenwood J .I I' (1974) ElcClrocaagulation in neurOSUl-gcry. Surg Neurol 2: 4 27. Gurdjian ES, Thomas LM, Gurdjian ES (1968) A singlc unit for bipo lar, rnollopolar coagulation, and cutting . ./ Ncurosurg 29: 567 -568

28. Hamby \VB (1952) Intracranial Anellrysms. Springfield , IL. Charles C Thomas Publisher 29. Hamby \VB (1969) Intracra nial surgery for a neurysms. Prog Neurol Surg 3: 1-65 30. Hamby \VB (1970) Remarkscollcerni ng intracranial aneurysm sU I·gery. Clin Neurosurg 17: 1- 17 31. Hocrenz P (1980- 198 1) T he operating microscope. J Microsurg I: 364-369, 419-427; 2: 22-26, 126-139: 3: 179- 182 32. Housepian EM, Ungcr \VH. Scharff TB et al (1975) Expericnce with videotape monitOring of microscopic neurosurgical procedu res. J Ncurosurg 42: 204 - 208 33 . Jacques S, Bullara LA, rudcnz RH (1976) Microvascular bipolar coagliJator. Technical note. J Neurosurg 44: 523 - 524 34. King TT, Worpo!e R (1972) Sel f-irrigating bilar diathermy forceps. J Neurosurg 37; 246247 35. K riegel' AJ (1978) The Use of the Operating Microscope. New York, Carl Zeiss 36. Kurze T (1964) Microtechniques in neurological surgery. Clin Neurosurg II : 128-137 37. Kurze T, A puzzo Mq , \\'eiss MH et aJ (1977) Expericnces with sterilization of the operating microscope. J Neurosurg 47: 861-863 38. Light RU (1945) Hemostasis in neul"Osurger r· .I Neurosurg 2: 414-434 39. Malis LI (1967) Bipolar coagulation in microsurgery. in Dtmaghy RMP, Ya§argil MG (cds) : Micro-vascular Surgery. Sw ug;m , G Thieme, pp 126- 130 40. Malis Ll (1979) Instrumentation and techn iques in microsurgery. Clin Neuros urg 26: 626-636 41. Nylen CO (1954) Thc microscope in aural surgery. IIS first use a nd later development. Acta O[olaryngol [Suppl] (Stockh) 116: 226- 240 42. Peerless SJ (1974) The surgical approach to middle cerebra l and posterior commu nicati ng ,IllC\lI·ysms. Clin Ncurosurg 21: 151- 16.? 43. Rand RW (1985) Micronellrosmgel)i cd 3 SI Louis, CV Mosby Co 44. Khoton AL, Merz W (1981) Suction lUbeS for con\'eI1lional and microscopic neurosurgery. Surg Neurol 15: 120 - 124 45. Robertson GE (1967) Pllellmoenuphalogm//hy, ed 2 Springfiel d, 1L, Charles C T ho mas Publisher 46. Rogers L (1930) T he history or craniotomy: an account of the methods which have been practiced and the instruments used for o pening the hu ma ll sk ull during life. Ann Med Hist 2:49:)514 47. ScarffTB (1974) A nell' bipolar suction-camery forceps fo r microncurosurgical use. Surg Neurol 2: 213 48. Sugita K (1985) Mic1"01Ie1lrOSlagicai Atlas. Berlin, Springer-Verlag 49. Sugita K, Hirota T, Tsugane K (1975) Applica-

2. I nstrumentation and Positioning

lion of nasopharyngeal mirror for aneurysm operation . Tech nical note. J Neurosurg 43: 244246 50. Sugita K, Kobayashi S, Shintani A el al (1979) fl. licroneurosurgery for aneurysms o f tile basilar artery.] Ncurosurg 51: 615-620 51. Sugita K, Kobayashi S. TakemaeT et al ( 1980) Direct retraction method in aneurysm surgery. J Neurosurg 53: 417 -419 52. Sugita K. Tsugane R (1974) Bipolar coagulator with automatic thcrmocomrol. Technical note. J Neurosurg 41: 777 - 779 53. Sugita K, Tsuganc R, Kagcyam3 N (1975) Bipolar coagulator with automatic thcnnocontrol and some impro\'cmciltsofmicrosurgicai insl!"u-

melliS, in Handa H (cd): Microneurosurgery. Baltimore, University Park Press, p 17 54. Wilson CB, Spetzler RE ( 1979) Operative approaches to aneurysms. Clin Neurosurg 26:232 - 247 55 . Ya~argil Me ( 1969) MicrosUlgery Applied to NeuroSllrgery. StUttgart, G Thieme, pp 119 - 143 56. Ya~argi l MG. FoxJL, Ray MW (1975) The operative approach to aneurysms oflhe anteriorcolllmunicating artery, in Krayenbiihl H (cd): AdMilas and Technical Stlllu/mtis in Neurosurgery, vol 2. New York, Springer-Verlag, pp 113- 170 57. Y.1.~argil MG, Vise WM, Bader DCH (1977) Technical adjuncts in neurosurgery_ Surg Neurol 8:33 1-336

3-Photographic Technique

Introduction T he color illustrations of live microsurgical a natomy as shown in this atlas were re produced from photographic color slides . The photogra phs were taken du ring actual ope rative proced ures per form ed by the author since 1975. They represcnL visual records o f selected surgical cases treated at the West Virginia University Medical Center in I'vlorgantown, West Virginia; the King Faisal Specialist Hospital and Research Centre in Riyadh , Saudi Arabia; a nd the Georgetown University Med ical Center in Washin gto n, D.C. T he majority of these cases were palie nt5 with illlracranial a ne u rysms, bu t the e mphasis he re is o n live anato my such as may be seen in the pterio nal

a pproach to many other lypeS of neurosurgical problems. Pho tog raph ic slides were selected for demo nstratio n o n the basis of ill ustrating clarity of features, having absence of significant tissue disto rtion by tumo r o r hemo rrhage, showing no rmal a natomic var iations, and/o r portraying special neuroa nalOmical points. From a recent historical stand point, the a uthor learned the photographic technique described herei n from trial-and-erro r expe rience a nd fro m lectures given by Leo nard Malis, Chairman of the De partmen t of Neurosurgery, Mount Sinai School of Medicine, New Yor k City. Earl y in his ex pe rie nce the a uthor VLF) was under the misconception that increased lightin g, a wide opening of the ca mera d iaphragm (small I-stop numbe r), and short time exposures were necessary lO gain sufficient ex posure of the image on the film in the prese nce of moveme nt of

neural and vasc ular intracran ial tissues refl ected by card iac pulsatio ns (directly on the blood vessels) and res pi ratory pulsations (indirectly via the venous circulation). Many surgical photogra phers still pho tograph through the operating microscope with these concepts in mind . However, in many instances, pholOgraphs taken with such techniques have lacked shar pness of image. appeared somewhat flat , and fa iled to provide a good de pth of fi eld . The key lO improving the q uality of the colo r photographs is to na rrow the le ns a perature (we use an f -StOp o f 44). T his results in a significant improvemen t in clarity a nd shar pness of images and in dep th of foc us (reducing the flatness of image effect). To accomplish th is o ne must increase the brightness of the ligh t source and/or increase the du ration of film exposure. The light inte nsity can be increased to some extent by overloading (increasing the voltage) the tra nsfo rmer of the 30- or 50-W tu ngsten bulb. Stro nger halogen o r xenon lig ht sou tcescan be used . But excess light ene rgy, even with the use of fi beroptic trans fe l~ dries out intracranial tissues rapidly and reasonable lim its a re finite. One can, however, extend the film expos ure time la, for example. 1 second . Because a rteria l systolic pu lsations are quite brief compared wi th the entire duratio n of one pulse. this movi ng (blurred) image is not detected by thc hu man eye o bserving the resultin g photo.. graph . In oth erwords, th is systolic movemem (or " noise") is ave raged out by the stable image of relatively much longer duration [4]. The surgical pho tographer muSl ta ke care to avoid any respiratory- induced move me nt by as king the anesthesiologist to hold the paticm 's respirations d u ring the du ration of fi lming if possible.

3. Photographic Tcch ni<Jue

In the a uthor's early yea rs of fi lming with use the right; the TV came ra is on the left; see narrow lens aperature and I-second exposu re Fig. 2.7). We have tried using special adapters limes, excel le nt color slides were obtained with allow in g the TV camera a nd still camera to be any sim ple came ra bacK (film holder) and with attached to the same side of the microscope's 30-\V incandescen t lig hting (givi ng a 2,800° to beam spl ineI' (permitting an observer's tube to 3,100° K color te mperature). Recen t a nd more be attached LO the other side), but the ca mera sophisticated ca meras, optics, and microscope lens aperatu re had to be wide ned (smaller [lighting systems have not improved the quality stop number) with a res ulti ng degradation of of the phoLOgraphs, and in many situations the the photographic image. quality deteriorated. The conve rsion o f some As reported previously [I, 2], the following Zeiss microscopes to the usc of halogen, were utilized by the author. For photography, tungsten-filament lam ps (giving a 3,200° to we used a Zeiss OPM I- I operating microscope 3,400° K color temperalUre) has improved the equipped wi th a 275-mm objective le ns, a 160lig ht inte nsity without noticeable degradation mm focal-l ength binocular tube, 12.5X in the photogra phic image on tungsten (ASA eye pieces, a 30-70 beam spli tter (70% of the o r ISO No. 160) Kodak Ektachrome film (ba- lig ht is deflected and divided equally between lanced for color temperatures of 3,200° K [4, the film on the right and the camera on the left; 5]). We have been satisfi ed with this light. 30% goes to the surgeon's eyes), a Zeiss came ra More recently we temporarily switched to adapter and 2x magnification auachment, a the use of the much brighte r xenon ligh t Contax camera body, a nd ISO (formerl y called source (shown on microscope in Fig. 2.5). How- ASA) No. 160 (tungste n) Ektachrome 35-mm ever, its color temperature is aro und 6,000° K. fi lm. T he tungsten- halogen light source was ils e miued liglll energy is stronger in the blue- used without auxiliary lig htin g but with the "overload " green spectrum (com pared wi th light from trans former constantly on tungslen-filamentlamps), and hence one must throug hout the operation. (If the heat is a luse daylight color slide film (Kodak's Ekta- lowed to escape directly into the room, the light chrome fi lm, ISO No. 200, is ba lanced at a bulb usually la sts throughout several operacolor temperature of 5,500° K). Unfortu - tions.) Before 1980 no drapes were used, but nately, the heat-absorbing (red-a bsorbin g) the microscope, camera, film, and T V system path ways of the microscope's optical system were cold-gas-ste rilized for 12 to 18 hours with further reduced the red speClrum in the lig ht, pure ethylene oxide gas. (New federa l regulaand the resulting photograph (even with day- tions have now restricted this method of sterililig ht film) portrayed defective color reproduc- zation.) Any black-paint border around the tion. White or g ray tissues had a yellow-green glass pris m deflecting the light through the obcast a nd red blood vessels had a browni sh cast jective lens was removed. Overhead lights in (due to the red and g reen color mixture). Al- the operating room were turned offLO provide though proper filters may improve the colo r, beller contrast and LO facilitate dilation of the the liglllioss may resu ltin no signi ficant netim- surgeon's pupils. provemem in bri ghtness with the xenon light Photographs \·...e re made with respirations source compared wi th the tungsten-halogen temporarily stopped or during the ex piratory light source. Accordingly, we have return ed to phase of the automatic respi rator and with the the tungsten-ha logen la mp on the Zeiss-Con- [stop on the Zeiss photoada pter set at44 . With lI'aves o peratin g microscope. nona utomatic cameras, the ex posure time was set at I second. Wi th automatic cameras the exposure time approxi mates this duration. We Current Techniques use the delayed sh utter-release mode so that a ll camera and microscope movements have Except for the Zeiss camera adapte r and 2x ceased by exposure time occurring about magnification attachme nt, the o ptics is that 12 seconds after pressing the exposure button. which is contained within the Zeiss operating Self-retaining retractors a nd while cottonoid s microscope system [3]. The still ca mera (cam- were posi tioned to provide lig ht reflcClions era back to hold and move the film; Fig. 3.1 ) within the wo und while avoid ing refl ectio ns tocan be any good-quality model and is attached ward the microscope. Unless otherwise indito the rig ht or left side of the beam splitter (we cated, the photographs presented were made

Currenl Techn iques

Fig. 3.1. Contax camera attached 10 microscope beam splitter via ad apter (not seen) alld 2x magnification attachment (arrow).

with the Zeiss magn ification dial set at its third magnification selling (the old No. 16 01' the new No. 1). providing a true 6x magni fication for the surgeon . Although lhe photographs lhemselves do not provide stereoscopic vision and sufficie nt depth of fi eld, which may be 6 em from the skull surface, the reader's knowledge of analom), wi ll compensate for this.

Bibliogra phy L Fox J L (1979) r.,I icrosurgical exposure of imracranial aTleurysms . .1 Microsurg I: 2- 31

2. Fox J L (1983) llitracranial Al1eUl ysms. New York, Springer-Verlag, vol 2 3. Hoerenz P (1980 - 1981) The operati ng microscope, J Microsurg I: 364 - 369, 419-427; 2: 22 - 26, 126 - 139;3: 179- 182 4. Malis LI (1981) Neurosu rgical photography thro ugh the microscope. Clin Neurosurg 28: 233 - 245 5. MartIn-Rodriguez JG (1985) Colo l' still and motion pholOgraphy and color tcle\Âˇisioll recording through the operating microscope, in Rand RW (00): MicrQrlclI.rosllrgery. SI Louis, CV Mosby Co. ed 3, pp 83-9)

--4 -Cranial Anatomy and the Cranial Flap

Anatomy The pterion has been defined in Chapter I. Figure 4. 1 illustrates that the pterion is not a specific point but rather a general region of the skull lying under the tcmporalis muscle and in dose prox im ity to the frontal, parietal, temporal, and sphenoid bones. The frontoparietal (coronal) sutu re and the sphenoidotemporal suture do not meet at a common point but in stead come to a "T' intersection (Fig. 4. 1) with the parietotemporal, parietosphenoidal. and frontosphcno idal sutures (the latter two forming a relatively straight posterior-ta-anterior extension of the parietotemporal suture). This anatomical arrangement allows a short common boundary betwee n the parietal and sphenoid bones and causes a separation between the fronta l and temporal bones.

Fig. 4.1_ View of left side of skull model . TIle suture lines between JX)rtions of the skull arc outlined in ink. F, frontal; P parietal; T, temporal; S, sphenoidal; and Z, zygomatic bones.

Figu re 4.2 shows the anatomical arra ngement of these bones at the inner base of the skull [I]. Although not prominent on the outside, the sphenoid bone represents the "keyslOne" of cranial-base analOmy. The word sphenoid is derived from the Greek word sphenoeides, meaning wedge-like [6]. From its body this interesting struclllre (Fig. 4.3) sends out lalerallesser and greater wings, a ppearing rather like a butterfly in flight [2]. For the surgeon operating at the base of the skull and brain, this hidden keystone contains landmarks of orientation as well as structures that may have to be removed by rongeurs and highspeed drills. The latter structures include the sphenoid wings, anterior clinoid process, posterior clinoid process, roof of optic canal, tubercu lum sellae, floor and septum of the sphenoid sinus, and floor of the sella turcica.

Fig. 4.2. Base of skull, upper surface. Note that Ihe anlerior clinoid process is a posterior projection of the origin of the lesser wing o f the sphenoid oone. Components of the sphenoid wing include lu, lesser wing; gu'. greater wi ng; ls, tuberculum sellae; ae, alilcrior clinoid process; sl, sell a lUrcica; pc. posterior clinoid pro ccss;fo, foramen ovate; ds, dors u m sellae. Redrawn from Clemente CD (ed) (198S)Al!alomyoj tht H/lInol! Body by H em)' Gmy, 30th American ed . Philadelph ia, Lea & l<"ebigcr, p 17 1 [ IJ.

Fig. 4.3. Vicw of disaniculatcd sphe noid bone o f sku ll as seen from behind . The dorsum sellae hides the sella turcica (pituitary fOS5<1) seen best from aoc·vcin Fig. 4.2. Note the relationship o f the greater and lesser wings separated by thcsupcriororbil.al fis· surc. A n o ptic strut separates the superio r o ,'hital fis· sure from the o ptic canal. From Etter L E (1955) Atlas of Roentgen AI/atomy of the Skull. Spri ngfield, 1L , Charles CThomas Publ isher. p 17 [2). V

The Cranial Flap By whatever approach to basal structures, the surgeon must have intimate knowledge of the sphe noid bone. The basal cran ial anatomy ta kes on a different pers pective when viewed in the surgica l upside-down, oblique position (see Figs. 2.3 and 4.8). Figures 4.4 and 4.5 illustrate a skull model with a small pterional cra nial opening. T hesc show the value of removing mu ch of the sphenoid wi ng (ie, lesser and greater wings) [3, 4]. Before the sphenoid win g is removed , the surgeon's view of the suprasellar region is blocked by the latcral projcClion of the win g unless greater and haza rdous brain retraction is a ppl ied . Partial removal of thc sphc noid wing, practiced for years by Walter Dand y's disciples, pcrmits a lowcr, basal, ta ngential a pproach to the circle of Willi s. Once the surgeon uses this tcchniquc rOUlinely a nd then omits it from an operative case, he will appreciate its significant value for permitting easie r visuali zation of basa l cistern s. This technique , coupl ed with the skilled usc of sel f-ret.'lining retractors and of the operating microscope on a relaxed brain , allows thc surgeon to manipulate microinstruments in small but sa tisfactoril y visualized spaces. If we take the same dry skull model shown in Figs. 4.4 a nd 4.5 , one can see the relationship of the basilar artery to the anterior a nd posterior cl inoid processes as visualized through a pterional exposu re (Figs. 4.6 and 4.7). One ca n unde rstand fro m Fig. 4.7 that removal of much of thc sphc noid wing on one side a nd a widely opened sylvian fi ssure on the othcr side arc necessary to approach the midbrain, pons, and inlerped uncular cislern wilh mi ni mal brain retraction. T he posterior clinoid process of the sphenoid bone then becomes a critica l la ndmark , lying medial to the oculomotor nerve passing forwa rd from the midbrain .

The Cranial Flap All surgica l photogra phs in this atlas arc shown as a right-sided pterional cran iotomy. Those that originally were left-sided have bee n reversed to permit consistency in anatomical il lu stration. Much of the following in th is cha pter is mod ified from a previous publication of the author [4 ].

For a right frontola tcral cra niotomy, the head is held in a t hree~point skull-fi xation apparatus (see Fig.2.3) and lUrned approximately 300 t045Â° to the left, tilted 150 to the left , and dropped back about 150 (Fig. 4.8). This brings the " psychopathic poi nt" (see Chapte r I) into the center and to thc highest point of the opc rative field . (When a right-handed surgeon operates on the left side of the head , a 40 0 to 450 rotation to the riglH is used.) For aneurysms of the middle cerebral a rtery or the internal carotid artery bifurcation, the head is dropped back further so that thc surgeon's line of vision is as perpendicular as possible to the M-I portion of the middle cerebral artcry. T he skin incisio n is kept behind the hairline rather than curvi ng for ward into the exposed forc head. This requi res a long incision, but the cosmetic resul t is better after the hair grows back. T he incision (Fig. 4.8) begins at the midline. curves laterally behi nd the hai rline, and terminates one fingerbreadth in front of the ear at the level of (or slightl), below) the zygomatic arch. T he skin flap and galea are stripped from the temporal is fasc ia a nd perios~ teum, covered with oxycellu lose gauze (colton may get ca ught in the high-speed drills), and pu lled fo rward with fi shhook retractors. An incision is made in the ante rior and postcrior lim il of the ex posed lemporalis muscle. T he anterior portion of the temporalis muscle is stripped posterioriy from the zygomatic process of the frontal OOne . Herc one may have to clectrocoagulate one or two bra nches of the anterior deep te mporal artery (from the imc rnal maxillary a rter y). Also. tiny art.eries pe rforating the frontal bone just behind its zygomatic process may have to be coagulated (wilh cuttin g current) and/or sealed with bonewax . The periosteum is stripped along the line of incision from the exposed fronta l, parietal, and lemporal bones. Howe,'er, a tria ngle of periosleum (Fig. 4.9) is preserved a nteriorly for later suturing to the te mporalis fasc ia, thereby coverin g the anterior frontal burr hole at the end of the operation. This piccc of periosteum , with its base anteriorly, is laid on the galea of the skin flap, covered with oxycellu lose, a nd held by a fi shhoo k retractor. The frontotempo ral bone fl ap itself is similar to that illustrated by Lud wig Kempe (sec Fig. \.5) with the fo llowing modifications (Fig. 4.10) ,

4. Cranial Anatomy and the Cran ial Flap

I. The first burr hole is just behind the

"psychopathic point" and its anterior ed ge touches on that point. 2. The second burr hole is also in the frontal bone. This hole lies more medial than that illustrated by Kempe (see Fig. 1.5). There are three advantages to this: (a) It allows more room for frontal lobe retraction without the retractor striking the fron tal bone. (b) It permils ple nty of room for maintenance oftemporalis muscle attachment to the frontOlcmperosphenoparietal bone flap, thereby reducing the incidence of later temporalis muscle atrophy. (c) T here is enough exposed bone flap for placement of flap-edge holes for suturclrubber band retraction of the bone fl a p. 3. The third burr hole is placed in the parietal bone just inferior to the temporal line. 4. The fourth burr hole is drilled in the temporal bone just in front of the ear a nd above the zygomatic arch. If placed too far back, temporal bone air cells may be encou ntered. The bone dust is saved and used to fill the burr holes after closure of the bone flap , thereby helping to preven1. a ny future inde ntations of the scalp into the burr holes. In patients younger than 55 years, the dura is not usually tightly adherent to the skull bone. In these cases we often utilize the ai r-driven craniotome to cut the sk ull fl ap in a similar design between two holes: only the most a nterior and the most inferoposterior burr holes. Otherwise a Gigli saw is used to cut the skull bone between the four burr holes. Prior to either of these techniques of craniotomy, rongeurs are used (we usually use the Echlin ronge ur) to bite away as much of a channel in the fronto-spheno-temporal bone as possible between the two basal burr holes under the temporalis muscle. Doing this before sawing the bone between the upper calvarial burr holes allows this inferior bony channel to be cut without the bone flap inad vertently fracturing too high above the base. After the bone fl a p is cut free, its inferior edge is rongeured (Leksell rongeur) until it presents a smooth , nonprojecti ng surface. Heavy si lk sutures are passed through two of the small edge holes (already drilled for future reattachment of the bone fl ap to the calvarium). The sutures are each connected to a rubber band that has been wrapped around

the rubber tubing shown previously in Figs. 2.7 A and 2.9. In this manner, the bone fl ap, still attached to the te mporalis muscle, is retracted over the zygomatic arch, thereby exposing the du ra (Fig. 4.11). The bone flap is waxed at its edges and then covered with wet oxycellulose. T he calvarial ed ges are also waxed . The dura is the n tacked up with sutures that are passed through the calvarial edge holes (also to be used for reattachmen t of the bone fl ap. T he sphe noid wing is rongeured infe riorly as far as possible and then waxed . In cases where an even more basal ex posure is required , we cut the zygomatic arch anteriorly and posteriorly. It can be left attached to soft tissues while the b ulk of the temporalis muscle is d isplaced inferiorly. The zygoma is reattached at the en d of the surgery. The superficial temporal artery runs in fron t of the ear and j ust su perficial to the galea. Preservation of this arte ry is useful, especially if the su rgeon pla ns an extracranialto- intracranial anastomosis . This may be necessary if one pla ns on a trapping procedure or an arterial occlusion. In such a circumstance, meticulous technique is needed to prevent superficial temporal arter y injury. The frontalis branches of the facial nerve pass forward between the galea a nd lemporalis fascia a nd are usually seen passing anteroinfe rior to the first burr hole. They can sometimes be preserved by turning a superfical layer of the temporalis fascia forward over the zygomatic process of the fro ntal bone before incising the tcmporalis muscle a nte riorly. Electrocoagu lation in the area must be ke pt at a minimum. T he ner ves a r e ofte n injured, and the patient may have an immobile forehead on the ipsilateral side foll owing surgery. In most such cases, frontalis mu scle function returns wi thin 6 month s.

Sphenoid Wing Removal The operating microscope is now brought into the surgical field and used unti l dural closure. The Leyla self-retaining retracto rs are attached to the operating table (see fig. 2.1 1). The dura of the frontal and temporal lobes are retracted gently from the sphe noid bone and the lateral roof of the orbit. If necessary, some cerebrospinal fluid (CSF) ca n be drained by

Sphenoid Wing Removal lumbar puncture to relieve pressure on the brain. Release only a sufficient amount of CS F to perm it a relaxed brain, as excess removal risks premaLUre rupture of an aneurysm, tearing of vcin s bridging the dura and the brain , or downward hern iation in cases with mass lesions. The dura of the temporal lobe is often quite vascular and will require bipolar electrocoagulation, oxycellulose application, and occasionally th e use of malleable dips. With a suction-irrigation apparatus in the left ha nd and a high-speed drill in the right ha nd (of a right-handed surgeon), the surgeon removes projections of the sphenoid win g and latera l orbital roof. Keep all couonoid s out of the immediate field to avoid injury by their being caught in the drill. The steel drill bit is used in itially because ofiLS more ra pid removal of bone. As the base of the anteriordinoid process is approached, the drill bit is changed to the d iamond type, which tends less to tear the nearby dura. The Lempert rongeur is very helpful in removing sliver-like projections of the sphenoid wing. A tiny bit of bonewax on a small , dry couonoid is a pplied against the bone with the bipolar forceps to stop bone bleeding. One mllst be careful to avoid drilling into the orbital cavity. I f this occurs, the patien t will have greater temporary swelling a nd ecchymosis of orbital tissues during the postoperative period. In some patiellLS there is a partial, congeni tal absence of the greater wing of the sphenoid bone behind the orbi t. The sphe noid wing is removed with a rongeur and then burred down with the highspeed drill dose to the base of the anterior clinoid process, a medial depth of about 5 cm (Figs. 4.12 and 4.13). As one approaches this point, the meningo-orbital artery (su praorbital branch of middle men ingeal artery) is a landmark seen in the dura; it passes from the middle men ingeal artery through its own "lacrimal" forame n (Hyrtl's canal) in the sphe noid wing or through the lateral corner of the su perior orbital fissure to communicate with the lacrimal a rtcry in the orbit. (This artery is one of the remnanLS of the e mbryonic stapedial arterial system [5]). The meningo-orbital artery usually is electrocoagulated and severed, allowing further drilli ng ofthe sphenoid wing.

At this point the faster steel drill bit is swi tched fo r a d iamond bit. The base of the amerior cl inoid process appears as a glistening while bone often contain ing a single small vascular channel (Fig. 4.13). The dural ope ning is considerably smaller than the craniotomy defect. The bony open ing is larger for the reasons stated earlier in this cha pter. The dura is perm itted to cover the brai n as much as possible to protect the brai n from the drying effecLS of air a nd light. T he dura is opened in a modified, shallow horseshoe-shaped man ner (Fig. 4. 14). The dural na p is retracted over the smoothed-out sphenoid bone by suturing it to the galea. Often a secondary dural inci sion over the sylvia n fissure is needed if the fi ssure is to be opened widely. At this point, some CS F can be removed by lumbar drai nage or by aspiration from the chiasmatic and adjacent ciste rns under a minimally elevated frontal lobe (Figs. 4.14 and 4.15). Auention must be paid to the one or more veins bridging the temporal lobe and the sphenoparietal sin us. Although it is good practice to preserve venous drainage where possible, we have not seen any com plications from electrocoagu lating and severin g these vei ns. I n cases where minimal temporal lobe retraction is necessary, these veins may be preserved . The following chapter details the anatomy of the sylvian fissure in the approach to the basal cisterns.

Bibliography (ed) ( 1985) Anatomy of Ille Human Body by Henry Gmy, 30th American ed. Philadelphia, Lea & Febigcr, p 171 2. Etter Lf. ( 1955) A/las of Roentgen Anatomy of lhe Skull. Springfield, 1L, Charles C Thomas PubI. Clemente C D

lisher, pp 16-44 3. FoxJL (1979) Microsurgical exposure of intracranial aneurysms.J Microsurg I : 2-31 4. Fox JL (1983) Intracranial Aneurysms, vol 2. New York, Springer-Verlag, pp 877-887, 1030

Lie TA (1983) Variations in cerebrovascular anatomy, in Fox J1. (ed): Intracranial Aneurysms, \'01 I. New York, Springer-Verlag, pp 432-489 6. Sin/man's Medical DicliOl!l1ry, ed 24. (1982) Baltimore, Williams & Wilkins Co, p 1312

4. Cranial Anatomy and the Cranial Flap

Fig. 4.4. View of dry skull in the same surgical position as in figs. 2.3 and 4.8 prior to removal of the sphe no id \~il\g. The right orbit is at the upper left corner. spit, L1.leral aspect of greater sphenoid wing;

pel, pClrous pyramid; ac, anterior clinoid proces; pc, tip of ]X>sterior clinoid process; crossed an-ow, exposed lOp of red rubber eraser ("lUmor" or ",jllcurysm").

Analo my

""'It

Fig. 4.5. Same dry skull as in Fig. 4.4. The sphenoid wing (sPh) has bee n drilled away. Crossed arraw: red rubber eraser ("tumo r" or "aneu rys m") sitting on lhe tuberculum sellae n anked by both ame rior

clino id processes. ac, Right amerior clinoid process;

pel, right petrous pyra mid ;,,ÂŁ;, righl posterior clino id process. From Fox [3] .

4. Cranial Anatomy and the Cranial Flap

Fig. 4.6. Same dry skull as in '-igs. 4.4 and 4.5. Skull is in upright, oblique position with view over lateral roof of orbil. zy. Frontal processofzygoma;pet. right petrous pyramid; ac, anterior clinoid processes

flank ing tubercu lum sellae (ts); PC. right posteriur clinoid process; 00, red pen representing basilar artery. (Behind the latter would be the midbrain and pons.)

AnalOmy

Fig. 4.7. Same dry skull as in Figs. 4.4-4.6. Sku ll now is in surgical upside-down, oblique position. Thesurgeon's view is more caudal to view the region of the "basilar artery" (00, a red pen) as seen via the pterional approach. The orbit is in the upper left

corner of the figure. pc, Right posterior clinoid process; pel, petrous pyramid; *, right anterior clinoid process: sph, drilled down sphenoid wing. From Fox [3).

4. Cranial Anatomy and the Cranial Flap

Fig. 4.8. Patient's head in a skull clamp. The incision (triallgle) isoudincd to stay behind the hairline. ret allows the bone nap to remain auached to the temporalis muscle. From I-ox [3).

The Cranial Flap

Fig. 4.9. Scalp nap turned for right pterional craniotomy. Paticnt in position shown in Fig. 4.8. Ga/~a exposed. Crosstd 01'7'01/,\ junction of tcmpo""dl line with orbital ridge a nd zygomatic process of f ron-

tal bone; fb. fronta l bone; If, tClllporalis fasc ia; pt. perioste um ; re, raney clips on scal p edgc; s, suction tube: If, thumb forceps elevating triangular patch of perioste um offfrontal bone Vb).

4. Cranial Anatomy and the Cranial Flap

Fig. 4.10. The oxycellulosc (ox) covered galea and scalp flap arc held by fishhook retraCLOrs (fit). A retractor (ret) is pulling the incised lcmporalis m uscle forward. One parietal (P). one temporal (I), and lWO

frontal if) burr holes have been drilled and covered with bonewax. fe, Periosteum; el, elevator; if, ternporalis fascia.

The Cranial Flap

Fig. 4.11. The bone flap (bj), covered byoxycell ulose has becn turned laterally o\Âˇe r the zygomatic arch. It rcmains attached to the temporalis muscle

(ox),

(t1ll). lph, Sphenoid ....,ing;td. temporal dura;fd. frontal dura : su, suture for later reattachment of the

bone flap .

4. Cranial AnatOmy and the Cranial Flap

/CO;

.1 Fig. 4.12. The sphenoid wi ng (sph) prior to removal. hII, Amcrior fronta l burr holc;fd, fron ta l dur<t;sf, dura over sylvian fissure; It!, temporal dura.

Sphenoid Wing Removal

Fig. 4. 13. The right sphenoid wing (spl!) has been burred away. Crossed arrow, vascular channel ill lesser wing of sphe noid wing near base of anterior clinoid process; mo, mcningo-orbital artery. On right is a re-

tractor on the dura of the tempo ral lobc (/d). On left is a suction tube (5) and retractor (ret) 0 11 the dura of the right frOlllallobe ifd). Zeiss dial SCl at magnification Hu mber 0.6 (old no. 10). From Fox [3].

4. Cranial Anatomy and the Cranial Flap

Fig. 4. 14. Initial exposure of carotid cistern. Magnificatio n reduced. Retractors (rtt) elc\'ating the right Ic mporallobe (about') and frontal lobe (below) I em frOIl1 right spheno id wing co\'c red by the turned-

down dural flap (dura), The sylvian fissure (sf) is not yet opened. 2, Optic nerve; ica, ime rnal carotid aftcry. Zeiss magnificatio n dial set at number 0.4 (old no. 6). From Fox [3].

Sphenoid Wing Removal

Fig. 4.15. View along sphenoid wing to the right anteriorclinoid process (*). ti. "I"emporal lobc;j1, fronlai lobe. The internal carotid artery (ica) and optic

nerve (2) are covered by arachnoid. J, Right olfactory tract ; s. suction lube. Zeiss dial set at 0.6 (old no. 10). From Fox (3).

5-The Sylvian Fissure

Introduction Even though the pterional approach to skullbase lesions has become more widely used by neurosurgcons, significam separation of the frontal and tcmporal lobes by opcning the sylvian fissure is often not done. However, as we have gained morc experience. we have o pened the sylvian fissure more and morc. This has seve ral benefits [3, 5): (a) small vessels arc not compressed by arachnoidal bands during retraction of the brain; (b) there is less resistance (and he nce less bra in-retractor pressure) to retraction of the fronta l lobe; (c) traction 011 onc lobe does not pull and injure Lhe other lobe; (d) fewer bridging veins need be sacrificed; (e) the olfactory nerve usually can be preserved; and (f) there is minimal traction on perforating arteries and on a n a neurysm.

Fig. 5.1. CT scan after injection of iopamidol into CS F. Arrow runs from posterior cerebral artery (at junction of ambient cistern with interpedu ncular cistern) to optic tract. Arrowhead. middle cerebral artery in sylvian fissure. Section is at level of midbrain and optic chiasm. Note anÂˇ tcrior cerebra l arteries in chiasmatic cistern (trianglt) and interhemispheric fi ssure.

Figure 5. 1 is a computed tomography (CT ) scan that nicel y ill ustrates the significant cerebral spinal fluid (CSF) space (sylvian cistern) between noncom pressed frontal and temporal lobes. This space, containing the midd le cerebral artery and its branches. is quite prominent in the older 01" the atrophied brain. h may be minimal in the edematous or compressed bra in. The sylvian cistern is larger near its basal zone, as seen in Fi g. 5.1. and becomes smalle r in the more peripheral zones. At the surface the sylvia n fi ssure may appear to be absent (i t is not) owin g to the close approximation of the froma l pia and temporal pia mater. This zone is covered by fi r mly adhering arachnoid strelched over th e pia, and at first observation the untutored observor may be mislead into believ ing that an opening of the sylvian fi ssure is too difficult to wa rrant performing. Indeed.

5. The Sylvian Fissure

the difficulties e ncountered with opening the sylvian fissure compressed by sofland edematous brain contai ning friable , nonautoregulating vessels may make the procedure LOa hazardou s. But in most circumstances the fissure can be widely opened, thus pe rmitting excellent exposure of basal anatomy between a drilled-down sphenoid wing and a widely exposed sylvian fissure.

Anatomy Figures 5.2 thro ug h 5.8 illustrate the initial opening of the sylvian fi ssure in five cases (all photographs in this alias a re presented as viewing the right side). With initia l elevation of the frontal and temporal lobes (Fig. 5.2), the surgeon will see fine arachnoid bands passing in the subdural space between the arachnoid and dura (both being mesodermal le ptomeningeal tissue of similar embryonic origin). I n some cases the arachnoid over the sylvian fi ssure is distended by contained CS F (Fig. 5.3). This often occurs when the brain has been mildly shrunken as water is transferred from the brain into the CS F space owi ng to controlled hyperve ntilation [7] . The sylvian fissure is usually opened on the frontal lobe side of the sylvian veins (Figs. 5.4-5.8). Initially, we use ajeweler's forceps to pick up the arachnoid (Fig. 5.6), which is incised with microscissors . The self-retaining retractor blades are e mployed to separate the frontal and temporal lobes, thus gently stre tchÂˇ ing the arachnoid in the fi ssure. This facilitates exposure of the next, dee per layer of arachnoid and its con tai ned peripheral branches of the middle cerebral arter y (Fig. 5.7). Close inspection via the operating microscope reveals the eve r-present, fine arachnoid bands or fibers supporting the arteries within their bath of CS F. This anatomical phenomenon, to be emphasized throughout this atlas, has been stressed by Arutiunov an d colleagues in their drawings [1]. They related mechanical distortion of these supporting fi bers to the evolution of vasospasm after aneurysmal subarachnoid hemorrhage. We no longer hesitate to coagulate and incise veins and supe rficial arteries passing between the two lobes. In this manner the surgeon, with the suction tu be in his left hand and the bipolar forceps o r microscissors in his right hand , works his way down toward the base of the sylvian fissure (Figs . 5.8-5.12). Meticulous ca re is

taken with the small a rach noid adhesions and bands adjacent to middle cerebral artery branches deeper in the fi ssure. When released , these bands will not compress a nd compromise vessels as the lobes are se parated, and the surgeon will find the fissure sudden ly opening up to sign ificant advantage. A small cotton paddy or dental cotton ball (counted ) is hel pful for compressing bleed ing vessels with the suctio n tube prior to their electrocoagulation. One finally reaches the much tougher arachnoid fibe rs at the base of the sylvian fissure (Figs. 5.9-5.1 1). When these arc cut, the surgeon ga ins immediate entra nce into the carotid cistern and more CSF is released. During this approach, the surgeon must decide whether or not to electrocoagu late a nd cutone or more bridg in g veins between the sylvian vei ns of the lemporal lobe and the dural sphenoparietal sin us (Figs. 5. 10-5 .1 3). Preservation of bridging veins generall y is a good policy, bUllheir presence may lim it adequa te exposu re in some cases. Also, these veins may lear, resulting in venous bleeding at a difficult time during the operation. We rarely, if ever, had a complication due to removal of these particular veins. Figure 5.13 shows the preliminary anatomy in one patient after opening the sylvian fissure. The following figures ill ustrate va riatio ns in surgical anatomy of the right sylvia n fissure. Figures 5.14 a nd 5. 15 are twO separate cases where on ly the d istal zone of the sylvian fissure (similar to site of jeweler's forceps in Fig. 5.6) has been o pened. In each case branches of the middle cerebral a rtery project out and arach noid bands a re noted. In Fig. 5.15 the morc superficial part of the sylvian fissure has been obliterated la terally by adhesions (from previous hemorrhage) between the frontal a nd temporal lobes. Figures 5.16 and 5. 17 are illustrations (at different magnifications) of middle cerebral arterial bra nches projecting outward after the lateral portions of the frontal and te mporal lobes in Fig. 5.15 have been scparated. Emphasis is placed on the arachnoid bands of Arutiunov ( I], which are clearly revealed in these photographs. Of course, normally they are bathed in CS F within the sylvian cistern . Figure 5.18 indicates a later state of dissection where the tough arachnoid between the base of the frontal lobe a nd the base of the temporal lobe is being severed by microscissors (compare with Fig. 5. 11 ). Figure 5. 19 shows a

Anatomy variation in the M-I and M-2 arterial anatomy after cutting basal arachnoid fibers. Figure 5.20 is an example of a long M-I artery projecting laterally through an early superficial opening of the sylvian fissure. Figure 5.21 illustrates another long M-I artery ta king the more usual course deep in the sylvian fissure. Figures 5.22 and 5.23 are exam ples of a long M-l artery and a short M-l artery, respectively. In both instances, the M-1 a rtery is best seen with the su rgeon's view aimed perpendicular to the axis of the artery, and this is best obtained by a greate rthan-usual extension of the patient's head when lesions along the M- l artery and internal carotid anery bifurcation are treated surgicall y. As the sylvian fissure is opened more widely at the base, the bifurcation of the internal ca rotid artery into its M-J and A- I branches comes into view. A structu re often seen but not commonly recognized here is the optic tract (Figs. 5.23-5.29). In this region the optic tract forms the lateral border of the lamina terminalis and its cistern , is crossed by the A-I artery, a nd lies deep to perforators passing to the a nterior perforated substance from A- J, M-I, a nd the carotid bifurcation vasculatu re. Figures 5.24 and 5.25 a re good examples of important anatomy seen at and just beyond the widely opened sylvian fi ssure. In addition to that described above. this anatomy includes the anterior choroidal artery, stria thalamic perforators. reCUITent artery of Heubncl; and the anterior temporal artery. Figures 5.26and 5.27 are additional examples where the internal carotid artery is short. The multitude of stria thalamic perforators as seen in Figu re 5.28 will be obscured by a n a neurysm at the bifurcation of the internal carotid artery (Fig. 5.29). In a n occasional case, gentle retraction to separate the fromal and temporal lobes will expose middle ce rebral artery branches usually deeply hidden in the sylvian fissure (Fig. 5.30). With microlechnique to open the arachnoid membrane and to sever the fine arachnoid bands supportin g the a rteries, the arteries (distended a nd pulsating with blood) may project outward toward the surgeon (Fig. 5.31). Usually a seco nd layer of arachnoid me mbrane is found covering the larger M-2 branches and must be removed to see these branches clearly (Fig. 5.32). These arteries then can be followed down to the M- I artery and its pe rforators (Fig. 5.33). It is thi s author's opinion that the brain is covered by a double layer of arachnoid

as if the brain had settled down onto a balloon made of arachnoid membrane. As the brain "settled," the opposing arachnoid walls approximated, leav ing an inner layer (wrapped around and supporting the arleries at the base of the brain) a nd a n outer layer (covering the brain and stretched between neu ral protrusions so as to form CS F-comaining cisterns and fi ssures). Ju st as fine arachnoid ba nd s and fibers run between the dura a nd the arachnoid (see Fig. 5.2), similar ba nds and fibers (of Arutiunov) run from the inner arachnoid layer (surrounding arteries) to other nearby inner or outer arachnoid layers (see Fig. 5.17). Often the inner layer of arachnoid el1\'elops not only the conduit arteries but also the perforators running in the CSF space between the artery and the brain (the anterior thalamic perforators from the posterior communicating ar'tery shown in Cha pter 8 bein g the best example). Thus, these perforators a ppear to be lined on both sides by a layer of inner arachnoid membrane [4]. This membrane becomes stretched, perforated, and discontinuous with growth of the child. Figures 5.34 and 5.35 are two illustrations of a leash of stria t halamic perforators passing from the M-I artery, through the base of the sylvia n cistern , over the optic tract, and into the a merior perforated substance. Figure 5.36 is an angiographic example of such perforators. The nex t chapter will ta ke the obser ver deeper into the carotid and adjacent cisterns.

Bibliography I. Arutiunov A, Baron MA, Majorova NA (1974)The role or mechanical ractors in the pathogenesis or short-term and prolonged spasm or the cerebral ancries. J Neurosurg40: 459 - 472 2. Fox JL (1979) Microsurgical exposure orintracranial aneurysms.] Microsurg I: 2-31 3. Fox JL (1983) Intmcrallial Aneurysms. vol 2. New York, Springer-Verlag, pp 877 - 1069 4. Fox JL, J erez A (1974) An unusual aCOustic neurinoma loca lized between brain stem and basilar arlery using emulsified Pantopaque cisternography. Surg Neurol 2: 329- 332 5. Fox JL, Albin MS, Sader DCH et al (1978) Microsurgical treatment of neurovascular disease. Neurosurgery 3: 285-337 6. )<ox JL, Nugent GR (1976) Recent advances in intracranial aneurysm surgery. \V Va Med J 72: 104- 106 7. Hayes GJ , Slocum HC (1962) The achievemem of optimal brain relaxation by hypervcntilation technics or anesthesia.J Neurosurg 19: 65-69

5. The Sylvian Fissure

Fig. 5.2. In itial intradural exposure down rig ht sphenoid wing. dum, Dura rencctcd over drillcddowlJ sphenoid wing: tlr, arach noid hands between

d ura and a rachnoid mcmbranc;jf, frolllal lobe; brain rClraClOrs; II. tcrnporallobc; ~ \'cin.

1l1,

Anatomy

•

r·

-. <

•

....~,

..f-,

••

.....,

•

. .. ~

)'.

fig. 5.3. Arachnoid membrane (ar) in sylvian fi ssure d istended by CS F. Prom inent sylvian vein (v) cov· ered by this arachnoid and divides peri pherally into twO branches (single-crossed arrows) entering

sphenoparietal si nus. clp. Malleable clips on d ural ed ge; If. lem porallobc;jl. fro ntal lobe; (lolJbie-crossed arrau~ a rachnoid on fronta l lobc side of sylvian veins.

5. The Sylvian Fissure

Fig. 5.4. In itial incision into sylvian fissure (arrows). This is 0 11 the fronta l lobe (jl) side of the syl\Âˇjan veins (v). Arachnoid membrane (ar, lOP) is stretched over

the sylvian fissure. A rach noid bands (ar. bottom) cross

a peripheral branch (a, bottom) of the middle cerebral artery. Abo\'c is a surface branch (a, toP) of the middle cerebral artery on the temporal lobe. rei, RetracLOr ; cot, cOllonoid.

AnaLOmy

Fig. 5.5. Same case ("ig. 5.4). Distal ponion of right sylvian fissure widely opened, exposing a large fronÂˇ tal M-2 arlery (m-2, bottom) and a smali lemporal M-2

anery (rn -2, loP). ica , Imernal carolid ancry (oU( of focu s) ;col,COltonoid u nder rClracLOr;j1, frontal lobe; If, lc mporal lobe;ar, arachnoid band.

5. The Sylvian Fissure

II (

dura

Fig. 5.6. Anothe r case illustrating jeweler"s forceps (jj) grabbing arachnoid over Syh,j.Ul fissure (arrow). fl. Fromallobe; II, temporal Jobc;d1lra, dural margi n;$, suction lU be; t', vein. From tox [3).

Anatomy

tl-ret

fI-ret

(

Fig. 5.7. Furthe r opening or syJvian fissure comaining entwining vessels. ar (toP), Arach noid on atherosclerotic internal carotid artery (ica); Ie, te ntorial edge; liÂˇret, temporal lobe rei ractor;jl-rel, rrontal

JolJe re tral:tor; v, syl vian veins. Note arachnoid bands (ar, bottom) octween sylvian vessels and pia. From Fox [3].

5. The Sylvian Fissure

tl.f'et

II-ret

Fig. 5.8. Another case to illustrate use of forcep blades ifcPl to open and separate arachnoid (ar) o n frontal lobe side of syl\'ian veins. /l-ret, Temporal lobe

rct ractor;jl-rel, fro ntal lobe retracLOr; col, small cott Oil

ball (from dental supply house).

Amllomy

Fig. 5.9. Arachnoid at base of sylvia n fissure is usuÂˇ ally thicke ned (ar) and needs to be cut to expose basal cisterns. gr, Gyrus rectuS; 2, optic ne .... ej ita, illlernal

carotid artery; dum, dura o,'cr sphenoid wi ng; 3, oculomotor nerve; v, veins;ti, temporallobe;fcp. forceps.

5. T he Sylvian fissure

Fig. 5.10. Another case after partial opening of arachnoid (ar, lOP) over sylvian fissure. Arachnoid bands (ar, hottom) connect branch (a) of middle cereÂˇ bral artery with pia. cot, Cottonoids under retractors;

fl. frontal lobe; 2, optic nerve; ica, internal carotid artery; pc, posterior clinoid process; v, sylvian veins; It, temporal lobe. T h e vei n (v, lOP) is entering the sphenoparietal sinus.

Anatom),

Fig. 5.11. Same case (Fig. 5.10) after further separation of arachnoid (ar, below) b)' blades of forceps ifcp}, or (toP), Arachnoid band O\'er optic nen'eJ

carotid arrer)' ju ncuon;pc, I>ostenor clino id process; V, vein; I'll, retractor on tcml>oraiiobe.

5. The Sylvian Fissure

Fig. 5.12. Same case (Fig. 5.10) after clearocoagulalion of vein (v) to sphenoparieta l sin us. dura, Dura over drilled-down sphenoid wing; te, tentorial edge;

me m, membrane of Liliequisl ill background (pointer crosses more supe rficial frontal lobe and internal carotid artcry) ;sc, microscissors.

Anatomy

Fig. 5.13. S.. me case (Fig. 5. 10) a rter rurthe r separalion o r rrontal lobe (j1) and te rn pordl lobe. The a rachnoid membrane or LilicquiSl (mem) has beCI1 partially opened. re\'ealing the basilar artcry (ba) in

the inter peduncula r cistern. T he uncus (un) is still adhercnt to thc ocu lo motor nerve (3). s. Suction tube; 2, optic nervc;pt:. posterior clinoid process; at , a nterio r clinoid process.

5. The Sylvian Fissure

(

r /1- 't

fig. 5.14. Another case after opening peripheral part of right sylvian fissure. Note arachnoid bands (ar) between arteries and between arterial branches and pia. The temporal (I) and frontal if) branches of

â&#x20AC;˘

the middle cerebral artery are projecting out of the depths of the sylvian fissure and toward the observer. rei, Retractor; Il, temporal lobe; fl. frontal lobe.

Anatomy

Fig. 5.15. Anothe r case after partial opening of right sylvian fissure (crossed arrow). Branch (a) of middle cerebral arter y lies on island of Reil (*) and comes from depths of sylvian fi ssure. ad, Adhesions (elec-

trocoagulated) between frontal lobe (jl) and temporallobe (If). col, Coltonoids under brain retractors; ar, arach noid band .

5. The Sylvian Fissure

Fig. 5.16. Same case (Fig. 5. 15) after further opening

of sylvi3n fissure . dura, Dura over drilled-down sphenoid wing; or, arachnoid membrane stretched between frontal and temporal lobes; Ii-ret, temporal lobe retractOr; floret, frontal lobe retractor. Note

many arachnoid bands between branches (a) of lhe middle cerebral artery and between arteries and pia (shown under greater magnification in the next figure).

AnalOmy

Fig. 5.17. Same case (Fig. 5.16) and vicw undcr grcater magnification (old Zeiss dial No. 25 or new Zeiss dial No. 1.6). Crossed arrows, examples of the many

arachnoid bands: col, coltonoid under retraclor;fl. frontal lobe.

5. The Sylvian Fissure

Fig. 5.18. Another case where arachnoid at base of sylvian fissure is being cut by microscissors. A suclion tube (s) is in the surgeon's Jcrt hand and microscissors are in his righl. The optic nerve (2) and the i/Hernal ca rotid artery (ica) a rc still covered by

arachnoid. cot, Small cOlton ball ; rtt, retractor o n frontal lobe ; v, vein from temporal lobe to sphenoparietal si nus; II, temporal lobe. From Fox [2].

Anatomy

Fig. 5.19. Example of 1\\'0 front..al (I:Mmom) and o ne te mporal (top) M-2 branches (m-2) arising from the M-I artery (m-/). on, Base of aneurysm with dome

buried in temporal lobe (If) ; ala, anterior temporal artery; v. \Âˇeins;j1. frontal lobe.

5. The SyJ vian Fissure

Fig. 5.20. Exampleof middlecerebral arter y pmjecting through partial o pening o f sylvian fi ssure. cot, Coltonoids under retractor;jl. frontallobc; an , twO microanc urysms of 1\'1- 1 artery (m - I) bifurcation; pia,

posterior temporal artery: fl, temporal lobe; I, tempol-al M-2 branch; G, small artery; v, vcins;f, frontal 1\'1-2 brauch.

Anatomy

Fig. 5.21. View along a widely opened right sylvian fissure uncler less magnification (old Zeiss dial No. 10 or !leI,' Zeiss dial No. 0.6). flÂˇrel, Fro ntal lobe retranor; 2, optic nerve; ica, imernal carotid artery; double-crossed arrfJUl, origin of anterior choroidal artery; single-crossel{ arrow. crosses dome of ica aneurysm and poims to posterior com mu nicati ng a r-

tcry dcep to aneurysm; ala, antcrior tcmporal artcry; Il-,.et, temporal lobe retractor; cot, couonoid ; 1/12, M-2 arteries arisi ng with multilobulated aneurysms at bifurcation of the M- I artery (m-/); ox, ox),cellulose (Surgicel);ar, arach noid bands;a-I, A- I artery. From "ox [3].

5. T he Syl\'ian Fissure

,,'

( Fig. 5.22. Example of long M-l artery (m-/) bu ried deep in right sylvian fissure. rei, Retractor on the tem poral lobe; cot, cOltonoid; v, \'ci ns; an, small aneurysm flanked by tempol'a] M-2 artery (loP) and

rronlal M-2 artery (bottom). NOle perforators sUlek to dome of aneurysm. ala , Anterior temporal artery. From Fox [2].

AnaLOmy

Fig. 5.23. Example of short M· I artery (m.I) at base of sylvian fissure. slw, Superior hypophyseal artery; ica, bifurcation of internal carotid artery ; ala, a n· terior temporal artery; an, small aneurysm nanked by temporal M·2 artery (t) and frontal ~1 -2 aner), (j);

p, perforating arteries ar ising from the A-I artery (a-I) and entering the a nterior perforated substance; at, optic tract. The M- I perforators are mostly hidden behind the M-l arte ry. From Fox [2].

ar, arach noid fibers enveloping perforators;

5. The S)'lvian Fissure

\ ~ . r?lu C?, ,

Fig. 5.24. Example of atherosclerotic internal carotid a rle ry (*) bifufcation seen after a wide opening of the sylvian fissure. mem, Dceply located membrane of Liliequist; a-I, A- I anery; mol, M-I arter),; ach, amcriorchoroidaJ artcry;ar, arachnoid band be-

tween artery and temporal lobe; I, temporal M-2 aftery;f, frontal M-2 artery; p, perforators from A-I and M-l anerics;o/, optic tract; v, veins; 110., ret:ur reru artery of Heubner; ch, optic chiasm.

Anatomy

Fig. 5.25. Internal carotid artery (ica) bifurcation at base of sylvian fissure (at higher magnification: old Zeiss dial No. 25 or new Zeiss dial No. 1.6). hp, hypothalamic perforators from internal carotid arÂˇ lery (ica); acll, anterior choroidal artery; mem, deepl y

located arachnoid membrane of Liliequist; m-l, M-I artery entering sylvian fissure; p, perforators from internal carotid and M-J arteries; ho., artery of Heubner; a-J, A-I artery; ret, frontal lobe retractor; ot, optic tract; eh, opticchiasm;ar, arachnoid bands.

5. The Sylvian Fissu re

...,." -,

'" gel

f[-ret

Fig. 5.26. Transsylvian view of M-J (m-l) and A-I (aJ) origins from internal carotid artery (ica). CrOSJed arrow, origin of anterior choroidal anery; pea, min iscule posterior communicating artery whose anterior thalamic perforaLOrs (p) are notable; 00, basila r artery in backgrou nd; sea, right superior cerebellar ar-

terYi 1'-1, large P_I artery; /l.ret, tcmporallobe retractorian, base of aneu rysm (from bi furcation o f basilar artery); ot, optic tract (see a<ljacent perforators from A-I l;jl-ret, frontal lobe retractor; gel, gelatin sponge (Gclfoam); ch, optic chiasm; 2, optic nerve; Pit, piLUilary stalk. From Fox [3].

Anatomy

Fig. 5.27. Another exam pic of transsylvian view of A-I (a-I) and M- I (m-l) origins fro m short internal carotid artery (iea). Note anterior thalam ic perforators a nd arachnoid bands coming off posterior communicating arlcry (pea) . Retraction of the uncus (unc) causes angulation of the oculomotor ncl"'-'c (3)

lateral to the postel-ior clinoid process (pe).fib, Fibrin from previous hcmorrhage; ala, anterior temporal arlery; m-2, M-2 artery; 01, optic tract; p, perforator fro m anery of Heu bner;jl-ret, fro ntal lobe retractor; cit, optic ch iasm; 2, optic nerve; ac, anterior clinoid process. From "ox (3].

5. T he Sylvian Fissure

Fig. 5.28. Another case where the internal carotid arlCry bifurcation (crQSMd arrow) is well seen after the sylvian fi ssure is widely opened. Note leash of arach noid bands and perforators (p) passing from A-

I (a-I) to the anterior perforated substance. ell, optic chiasm; Qt, optic tracl; 00, basilar artery;slm, superior hypo physeal arlcry;o7l, aneurysm orica at rakeoffof anterior choroidal aftery; m-I, M-l artery.

Anatomy

Fig. 5.29. Base of aneurysm (an) at bifurcation of inlernal carotid artery (ica), transsylvian view. Artery of He ubner (1m) is adherent to aneurysm. a-I, A- I artcry; If, lamina terminal is; ot, optic tract; adm, a n-

terior choroidal artery; pea, posterior commun ic.1.ting artery; If, temporal lobe; m_l. M- J aner)';cof, cOttonoid ; 1111, rctractoTs;j1, frontal lobe. From Fox [3] .

5. The Sylvian Fissure

Fig. 5.30. Anothe r case illustrating the anatomy o f the right syJvian fissure. Arachnoid still CQ\'c r s the sylvian fissure (between crossed arrows) in which the

arteries arc exposed by separation of the frontal (jl) and temporal (tf) lobes. rei, Retractor; spit, dura rcnected over sphenoid wing; v. vein.

Anatomy

Fig. 5.31. Same case (Fig. 5.30) after the arachnoid over the sylvian fissure has been opened. Peripheral branches (a) of the middle cerebra l artery project the mselves toward the surgeon. Deeper M-2

(ar)

branches remain covered by a deeper layer of arachnoid (crossed arrow). Note strands of arachnoid fibers supporting the arteries. *, Unseparated deepe r portions of the froma l and temporal lobes.

5. The Syh'ian Fissure

Fig. 5.32. Same case (Fig. 5.30) after removal of the deeper arachnoid layer. The frontal MÂˇ2 branch (single-cros.sed arrow) and the temporal M-2 branch

(dQuble-trOSMd an-ow) are seen. ala, Aillcrior temporal artery.

Anatomy

". Fig. 5.33. Same easc (Fig. 5.30) aflcrcxposurc of the M- I arter}' (m-l) deep in the sylvian fiss ure. T he M- I division into the frontal (single-crossed arrow) and temporal (double.crossed arrow) is seen. Note leash of stria thalamic perforators (perf) passing from M-l.

crossi ng the right op tic tract (ot), and enter ing thc antcrior perforated substance under the frontal lobc retractor (ret). fl, Temporal lobe; an, giant internal carotid aneurysm; ala, anterior temporal arter y.

5. The Sylvian Fissure

}

Fig. 5.34. Samccase (Fig. 5.30) with more magni fied view of ]\,1Âˇ I (1/1+ 1) perforators. pel[. One of man)' M-l perforaLOrs; m-2, M-2 arteries; rei, fro mal lobe re-

tractor;

01,

optic tract; an, aneurysm;

arachnoid fibers from art.eries.

(1.1;

linc

Anatomy

.I! Fig. 5.35. Another case showing arterial anatomy of base of right sylvian fissure. Note unusually large perforator (double-crossed arrow) arising from the M1 arte ry (m-/). II, Te mporal lobe ; ala, anterior temporal artery; lia, arte ry of Heubner; 01, optic tract;j1,

fmnla1 lobe; aI; arachnoid fibers; a- I, A- I artery; eh, o ptic chiasm; iea, internal camtid artery; pea, posterior communicating artery; single-crossed arrow. anterior choroidal anery.

5. The Syh"ian Fissure

Fig. 5.36. Left internal carotid ancriogram illustrating stria thalamic perforators frolll lhe M- I and A-I arteries. Patient had aneurysm (arrow) alorigin of A- I and al origin ofantcl"ior choroidal artery. From Fox and Nugent [61 with permission from the West Virgin ia State l\Iedical Association.

6-The Carotid Cistern and Environs

Introduction The carotid cistern, the chiasmatic cistern, and the cistern of the lamina lcrminalis lie rostral to the arachnoid membrane of Liliequist (membrane of Key and Retzius). Surgical observations regard ing the cerebral spinal nuid (CSF) cisterns and their companmental divisions arc described elsewhere [3]. Fig ure 6.1 is a coronal com pUled tomography (CT) image (a cisternogram) that nicely illustrates the rela tions hip of the illlcrnal carotid artery to the carotid cis-

tern bounded late rall y by the medial portion of the temporal lobe. Posteriorly the carotid cistern is separated from the interpeduncular cistern (see Chapter 8) by the arachnoid membrane of Lilicquisl; mediall y the carotid cistern joins the chiasmatic and lamina terminalis ciste rns and superiorly it joins the sylvian cistern (fi ssure) . In Fig. 6 .1 note the bifurcation of the internal carotid artery into the middle cerebral artery (r..'I- 1 segment) and the anterior cerebral artery (A- I segment). This occurs altheconfluence of thc uppe r pan of the carotid cistcrn,

Fig. 6.1. Cisternogram with iopamidol in CS Fimaged by coronal CTscan LO show anatomyofi mernal carotid artery (black (/),-ow) wilh cisterns and brain . Open arrow, A-I arter), ; black arrowhead, optic chiasm; while arrowhead, uncus of temporallobc; wltill' (j/TOU\ contrasl medium in s)'Jvian fissure (cistern). See text.

6. The Carotid Cistern and Environs

Fig. 6.2. Tomographic image after ai r has replaced some CSF by pneumoencephalography (patieotin sitting position). Closed G/'rQW, lies in interpeduncular cistern and poims to arachnoid membrane of Liliequisl (Key and Retzius). Open arrow, ai r in aqueduct ofSylvius. Sec text.

the lower-medial pan of the sylvian cistern (containing the M- I origi n), a nd the upper-late ral part of the chiasmatic ciste rn (containing the A- I origin ). This confluence is bounded superiorly by the anterior per forated substance of the fronta l lobe . In earlier years when pneumoencepha lography was a common intracranial imaging pro-

passes from side to side between both oculomotor nerves (see Fig. 8.1). Normally it is either a solid , translucent sheet with openings on either side or a multi perforated membrane allowing passage of CSF from the posterior fossa into the anterior cisterns, from whe nce CSF circulation continues ove r the surface of the brain. After subarachnoid hemorrhage or cedure, the injected gas (usually air), which re- meningitis, ad hesions a long this membrane placed or displaced some of the CS F. often was may sea l offCSF passageways a nd ca use a comtemporarily trapped in the interpeduncular municating hydrocephalus. Opening eithe r cistern (Fig. 6.2). The air was prevented from this mem bra ne or the la mina terminalis at passing throu gh me mbrane openings and into surgery releases much CSF and may be a perthe anterior cisterns by the membrane of manent cure for patients with hydrocephalus. Liliequist until a sufficien t pressure differen- Unless one is approaching a lesion in the intertial developed to overcome adhesive forces be- peduncular cistern or attempting lO release tween the air bubbles and the moist a rachnoid CS F from the posterior cisterns, it is bette r to leave the Liliequist me mbrane intact. It acts as membra nes . The membrane of Liliequist. known origi- an effeCli ve barrier to surgical blood entering nally as the membrane of Key and Retzius. is an the posterior basal cisterns. Further details are important arachnoid landmark [2]. The mem- given in anothe r textbook [2]. brane run s from the dorsum sellae and posterior clinoid processes upward toward the mammillary bodies of the hypothalamus. It

Anatomy

Anatomy The surgical anatomy prcscmcd in this alias is oriented as the surgeon sees it through the operating microscope at surgery. It is always de picted on the right side of the patient for observer consistency, and the reader may need to refe r to the figures in Chapter 4 (especially Fig.4.8) for occasional orientation of the supine patie nt's head. T he right olfactory tract will always head toward the upper-left corner of the figure (towa rd the paticm's nose), and the righl lcmporallobc (usually its uncus) will lie und er a ribbon retractor 011 the right side o f the field (toward the paliem's riglll ear). Now that the sylvian fi ssure has been opened (Cha pter 5), the surgeon recognizes normal (or abnormal) va riations in surgical anatomy as seen between the basc of the sylvian fissu re a nd the dura reflccted ovcr the drilleddown a nd surgically fl attc ncd sphenoid wing ( ~igs. 6.3 a nd 6.4). The fi rst visible branch of the internal carotid artcry is usuall}' not lhe ophthalmic a rtery, for the origin of the ophthalmic artery invariably is hidden by the superiorly a nd medially overlapping optic nerve. The ophthalmic a rtery usually arises on the medial side of the carotid artery just below. above. or at the level of the exit of the carotid a rte ry from thc cavernous sinus. Most commonly the surgeon first recognizes the ori gin o f the posterior communicating artery on thc latcral , poste rior, or posterolateral side of the ca rotid artery; but on close inspection onc can see more proximal (ie. toward the heart) arterial branches, which are the superior hypophyseal a rtery (Fig. 6.4) and hypophyseal perforators. Throughollt this cha pter the reader will note how close the internal carotid artery comes to the posterior clinoid process. and at times its bifurcation is behind the level of the dorsum sellae. The oculomotor nerve (third cra nial nerve) always lies external to the posterior cl inoid process. as this nerve passes forward under thc a nterior reflcction of the tentorium and into the top of the cavernous sinus (sec Figs. 8.2 and 8.3). T he intracran ial portion of the internal carotid artery may be fairly long, as noted in Figs. 6.3 a nd 6.4, or short, as demonstrated in ~igs. 6.5 a nd 6.6. T he shorter this internal carotid ar tery segment. the more readily the

su rgeon can expose the origins of the A-I and M- I branches. A leash of vital perforating artcries arises from the posteroinferior side of the internal carotid artcry and the posterior communicating a rtery (Figs. 6.7 and 6.8). Often one has to retract the carotid artc ry medially or laterall y to sce thcm. Thcse perforators include the superior hypoph yseal artcry. hypophyseal perforators, and anterior thalamic perforators. As the surgeon retracts the frontal lobe. the olfactory tract a nd gyrus rectus come into view. Co mmonly, thc r ecurrcnt artery of Hc ubner (pc rforator fro m the antcrior cerebral artery) is seen in the Cl"cvicc between the retracted frontal lobe and the optic nerve (Fig. 6.7). Whc n la rge, this may be mistaken for the A-I artery, which lies behind (o r in front) and below the artery of Hcubner. As one retracts the temporal lobe, a major inte rnal carotid artery branch within the carotid cistern will be the an tcriorchoroidal artcry or arteries (frequently there may be two or evcn three) as illustrated in Figs. 6.9 and 6.10. This a rtcry arises laterally, postcriorly, or posterolatera lly from the internal carotid artery and passes posteriorl y under the uncus of the tempora l lobe. II. enters the choroid fi ssure and passes thence into the temporal horn . As this a rte ry travels back, it may come in close proximity to the bifurcation of the internal ca rotid artcry and its perforators. The poste rior communicating artery may be seen dec p to the space between the carotid arÂˇ tery a nd the optic nc rve (see Figs. 6.6 and 6.9). or it may bowolltlatc raliy as show n in Figs . 6.11 and 6.12. Even when the posterior CO Ill municating artery is small (Figs. 6. 13 a nd 6.14), it will contain vital a nterior thalamic perforators to the brainstem. Ofte n an infundibulum of the posterior communicating artery is seen, a nd its a ppearance suggests a prcancurysmal a nomaly (Fig. 6.15) dcveloping at the d istal angle between internal carotid artery and the posterior communicating artery, the classical si tc of such ane urysms (Fig. 6.16). Although the pituitary stalk lics in the back of the chiasmatic cistc rn, it often is readily identificd upon exposure of the carotid ciste rn . As shown in Figs. 6.7 and 6. 11, for example, the ptcrional approach renders the pituitary stalk visible through the space betwecn thc

6. The Carotid Cistern and Environs

Table 6.1. Structures contained within the carotid 6sterns' ,

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. II. 12. 13. 14. 15. 16. 17. 18.

Internal carotid artery Origin of the ophthalmic artery (not always) Origin of the superior hypophyseal anery Origin of the posterior communicating anery Origin of the anterior choroidal artery Origin orlhe middle cerebral artery (M- I) Origin orthe anterior cerebral arte ry (AÂˇl) Origins of the hypothalamic perforators from the carotid artery Origins of the more rostral anterior thalamic perforators Some stria thalamic perforatorll A portion orthe artery of Heubner A portion of Ihe ante rior perfo ralCd substance of the frontal lobe Medial surface orthe temporal lobe Lateral border orlhe optic nerve Sympathetk fibers on the internal carotid artery Rostral edge of the posterior clinoid process (dural covering) Anterio r cli noid process (du ral covering) A portioll of the tentOrial edge between the anterior and postcrior clinoid processes

Items 12-14 and 16-18 can be considered to form portions of the margins of the carotid cistern. Sec Fig. 6.1.

oplic apparatus a nd the carotid artery. The slalk lies between the arachnoid membrane of Liliequisl posteriorl y and the optic chiasm anteriorly. It appears as a reddish, vascu larized projection passing inferiorl y through the opening in th e diaphragm sellae. T he su perior hypophyseal artery a nd hypothalamic perforators provide a rich ane rial blood supply, and the ponal plexu s of veins also are visible under microscope. Regard less of the location of the lesion, we not only open the sylvian fiss ure substantiall y but we also lyse adhesions and arachnoid (which separates the carotid and chiasmatic cisterns) between the ipsilatera l optic nerve a nd the base of the frontal lobe whe n usi ng the pterional approach (Figs. 6.1 7 and 6. 18). This allows: (a) gentle retraction of the frontal lobe without adhesions pulli ng on the optic nerve, (b) less brain retraction press ure, (c) occasional inspeClion of the anterior communicating complex in aneurysm cases, (d ) exposure of the lamina tcrminalis in cases with hydrocephalus, and (e) assessment of local anatomical variations and e nhance ment of the surgeon's knowledge of surgical anatomy. In our experience the latte r is done at no risk [Q the patient a nd has bee n extremely important in honing the surgeon's skills. in patients without lesions in the anterior communicating region,

actual exposure of the anterior communicating a nery is not done in pa tients who would require significant frontal lobe retraction . Figures 6.19 a nd 6.20 illu strate how, in some cases, the internal ca rotid artery ca n exte nd or project above and behind the level of the poste rior clinoid processes and the dorsum sellae. Here we are looking med ially behind the optic apparatus (nerve, chiasm, and traCl) ; the lOp and side of the dorsum sellae are brought into vIew. Although not proved histologically in this case (Fig. 6.21), we believe that sympathetic fibers are seen traveling on the adventitia of the internal carotid anery in the carotid cistern. T hey ca n be mistaken for arachnoid bands and vIce versa. Upon elevation of the fro ntal lobes in the nonswollen brain , a view of the medial side of the opposite carotid cistern can be visualized (Fig. 6.22). Note how the medial side of the temporal lobe forms the lateral boundary of the carotid cistern. Figures 6.23 a nd 6.24 again show how the carotid cistern is bounded behind by the arachnoid membrane of Lil iequist, above by the a nte rior perforated substance, laterally by the tem poral lobe, and mediall y by the chiasmatic cistern. T he membrane of Liliequist appears blue whe n CSF remains behind it in the interped uncular cistern. The

Anatomy color turns black when the CS F is drained (eg, by aspiration or lu mbar puncture) so as to leave only a shadowed space without the reflecting and refracting water (CSF). Note the unusual veins (bilateral) from the unseen cavernous sinus to the unseen basilar vein of Rosenthal , the unusual position of the pituitary gland in a shallow pituitary fossa, the portal veins on the pituitary stalk , and the opposite posterior communicating artery seen through the space between the optic nerves. Figures 6.25 and 6.26 represent another exam ple of the carotid cistern and environs. Note the su pe rior hypophyseal artery, pituitary stalk, and anterior thalamic perforators with hypophyseal perforators (displaced me-

dially by giant aneu rysm). Table 6.1 summaries the various structures found in the carotid cistern. The next chapter will take us i~to the more med ial chiasmatic and adjacent cIsterns.

Bibliography I. Fox JL (1979) Microsurgical exposure ofintracranial aneurysms. J Microsurg I: 2-31 2. Fox JL (1983) IntmcranUiI Aneurysms. New York, Springer-Verlag, frontispiece, pp 877 - \069 3. Ya~argil MG, Kasdaglis K, Jain KK et al (1976) Anatomical obser vations of the subarachnoid cisterns of the brain during surgery. J Neurosurg 44:298-302

6. The Carotid Cistern and Environs

Fig. 6.3. View of right carotid cistern and environs. aI', Arachnoid membrane between the optic nerves; 1, olfactory trdct; gr, gyrus rcctus; 2, right optic

nerve; Ttl, retractor on frontal lobe; crossed arrow, origin of the posterior communicating artery; ica, internal carotid artery; 3, oculo motor nerve passing forward uncler the morc lateral tentorial edge (Ie), by the more medial posterior clinoid process (PC) and thence imo the C3\'e rn OUS sinus; mem, a refleClion of

Liliequisl's mcmhl<tlle. Between the ocu lomotor nerve and Liliequisl's membrane is a black, dear CSF passageway into the interpeduncular cistern. Note the attachment of Liliequist's arachnoidal membrane to the posterior clinoid and adjacent dors um sellae. Opening this membrane between the oculomotor ne rve and the internal carotid artery is the usual frolllolatcra l route to the interpeduncular cistern. From ~ox [ I].

Anatomy

Fig.6.4. Carotid cistcrn in another patient. or, Arachnoid between optic nerves; 2, right optic nerve; slUJ, superior hypophyseal artery; ica, internal carotid artery; Ie, anterior reflection of tentorial edge, 3, oculomotor nerve passing late ral to duraon

posterior d inoid process (PC); pea, posterior comÂˇ municating anery; mem, membrane of Liliequist;flÂˇ rei , fro mallobe retractor; 1, ol factory tract; v, vein 011 gyrus rectus (gr). From Fox [2].

100

6. The Carotid Cistern and Environs

Fig. 6.5. Right carotid cistern with shon internal carotid artery (ica). 2, Optic nerve; ac, anterior clinoid process; mem, membrane of Liliequisl (cover. ing posterior clinoid process); pea, origin of posterior communicating artery; ), oculo motor nerve;

ad, adhesions between aneurysm (an) and temporal

lobe (/l);cot, couonoid;ata, anterior temporal artery;

crossed arrow, origin of anterior choroidal artery; bif, bifurcation of carotid artery; fri, origin of A-I artery;ft. frontal lobe. From Fox [2].

Anatomy

Fig. 6.6. Anotherexample of a short internal carotid artery (ica) . Note yellow atherosclerotic plaque. pea, Origin of posterior commun icating artery (lateral pea) passing behind carotid artery and reappearing deep to space betwcen optic nerve (2) a nd carotid arÂˇ

101

{cry; gel, Gelfoam on optic nerve; a-I, right A- I artcry; bif, bifurcation of carotid artery; ret, temporal lobe retractor; an, a neurysm ; ad, adhesions between aneurysm and tentorium (te). From Fox [ I].

102

6. The Carotid Cistern and Environs

Fig. 6.7. Example of long atherosclerotic internal carotid artery (ica) and environs. Many hypothalamic (including superior hypo physeal artery) and anterior thalamic perforators (enclosed in an envelope of arachnoid) arc seen passing back and medially from the carotid artery and the posterior communicating artery (pea). peif, One of these per-

rorators coming off the carotid ancry;), oculomotor nerve, tl, uncus of temporal lobe;jl. frOlltal lobe; ret, retractOr ; J, olfaClory tract; ar, arachnoid between optic nCfI'CS; 2, right optic nerve; JUl, recu rre nt artery of Heubner;pil, vascular pituitarystalk ;pc, d u ra on posterior clinoid process. f rom Fox [2].

Anawmy

103

1( ,, / I

, /

Fig. 6.8. Greatly magn ified view between right optic tract (ot) and internal carotid artery (ica). Zeiss dial set at No. 2.5 (old No. 40). Anterior thalamic perfOTawrs(jJeifj from carotid aneryand posterior com -

municating artery (pca) are seen. 2, Optic nen-e; mem , membrane of Liliequist; pro probe retracting carotid artery laterally. From Fox [I].

104

6. The Carotid Cistern and Environs

"',

Fig. 6.9. Carotid cistern with origins of posterior communicating artery (pea) and anterior choroidal artery (acha) from internal carotid artery (jea). mem, Membrane of Liliequist; an, aneurysm; 3, oculo-

mOLOr ncrvc;ad, adhesions between frontal lobe and optic tract (ot); pit, pituitary stalk; 2, optic nerve; 00, origin of ophthalmic artery; ret, retractors. From Fox [2].

Anatomy

105

Fig. 6.10. View of carotid cistern showi ng relationship of anterior choroidal anery (acha) to the uncus (tine) of the temporal lobe./I(1., Anery of Heubner; J, olfactory tract; gr. gyrus rectus; 2, optic nerve; iea. inlel'llal ca rotid arlery; pea, origin of posterior comÂˇ munica ting anery; Ie, tentorial edge; all, aneurysm

(shrunken and elongated by bipolar electrocoagulation) ; ad, adhesions and fibrin between aneurysm and temporal lobe and tentorium. Deep to the anterior choroidal a n e ry (adUJ) lies the arachnoid me mbrdne of LiliequisL From Fox [I].

106

6, The Carotid Cistern and Environs

Fig.6. 1I. View o f carotid cistern with laterally d iÂˇ rected posterior communicating artery (pea). mol, M-l origin;peif, perforators from A-I (a-I); ot, right optic tract; Jryp, hypothalamic perforaLOrs from carotid artery; pil, pituitary stalk; ch, optic chiasm; 2, left and right optic nerves; (-ica, medial side ofleft ill-

lernal carotid artery; dia, diaphragm sellae; pc, left posterior clinoid process; crossed arrow, superior hypophyseal artery; r-ica, right internal carotid artery; r-pc, right posterior clinoid process; ), oculomotor !len"e. From Fox [2J.

AnalOmy

Fig. 6.12. A very athcrosclerOlic imcrnal carotid artery (ica ) with the posterior communicating artery (fxa) goi ng latcrally. Crosud arr~ crosses dome or atherosclerotic ane urysm and points to perforator. adm, Ante rior choroidal artery; 00, basitar arter), lying in imerpeduncular cistern a nd seen arter re-

107

mova l of membralle or Lilicquist (In.!m) still attached to oculomOlOr ncn'e (J) and posterior clinoid process (PC), rtt, Retractor on right temporal lobe; te, tenlorial edge; at:, anterior clinoid process; 2, optic nerve,

108

6. The CarOlid Cistern and Environs

--=- ---

Fig. 6.13. Example of small, short posterior communicating artery (crossed arrow) connecting internal carotid artery (ica) with posterior cerebral artery (p2). cot, Cotlonoid; unc, uncus of temporal lobe; an , small aneurysm at takeoff of anterior choroidal artery ;

cot

m- I, origin of M-I artery; a- I, origin of A-J artery;lUl, artery of Heubner; 01, optic tract; 2, optic nerve; ac, anterior clinoid process; pc, posterior clinoid process; te, tentorial edge; ), ocu lomotor nerve. From Fox (2].

109

Anatomy

""'

\ Fig. 6.14. Same case as Fig. 6. 13 with probe (pr) displacing carotid artery medially. Crossed arrow, site of anterior thalam ic perforators from posteriOlÂˇ com-

municating artery; 01, optic tract; pc, posterior clinoid process; p- J, P-l artery; 3, oculomotor nerve; unc, uncus;p-2, P-2 artery.

110

6. The Carotid Cistern and Environs

Fig. 6.15. Example of prcaneurysmal type of infu ndibulum (croSMd af7"ow) of posterio r com municating artery (pea). perf. Anterior thalamic perfor.uors; adm, aillcrior choroidal anc!)' ; V, vein; a-l, A-I artery; Qt, OPlic tract; fl-rt/, frama l lobe retractor ; pro

probe retracting carotid artcl1' i Pit, pituitary stalk; 2, optic ncn'c;llC, anlcrio r di no id process; un, internal ca rotid artery; Ie, te ntorial edge; pc. postcriordinoid process; J, oculomotor Ilcn'c; II-rei, temporal lobe rctractor. From ,"ox [2].

III

Anatomy

mom

Fig. 6.16. Carotid cistern after bipolar eleclrocoaguÂˇ lalion of aneurysm (an) with ad hesions (ad) to ocu lomotor nerve (3) and uncus (unc) of tcmporal lobe. col, Cottonoids; mem , membrane of Liliequist

oot

(or Kcy and Retzius); ac, autcrior clinoid proccss; ica, internal carotid artery; pc, posterior clinoid process; pea, origin of postcl'ior communicati ng artcry. From Fox [2].

112

6. The Carotid Cistern and Environs

Fig. 6.17. Anatomy of carotid cistern and e nvirons. Arachnoid membrane of Liliequisl(mem) is well seen deep to and between the internal carotid artery (ica) and oculomotor ne rve (3). Crossed arrow, anterior choroidal artery; IInc, uncus; mÂˇl, origin of M-l artcr),; an, base of aneurysm at bifurcation of carotid artery; a-1, righ t A-I al"ter}'; a-a,junction of right A- I and unseen rig ht A-2 and anterior communicating

(aea) arteries; gr, r ight gyrus rectus; perf, per forators

from anterior communicating artery; hr, bridging artcry from anterior communicating artery to left A-2 artery (connection out of view); a-2, Icrt A-2 artery; 2, optic nerves; ch. optic chiasm; ft, lamina terminalis; ot, r ight optic tract; ac, ante rior clinoid process; ds, diaphragm sel lae; pc, posterior cli noid process; pea, posterior communicating artery.

Anatomy

Fig. 6.18. Sa me case as Fig. 6.17. Upper internal carotid artery (ica) and the M- I origin (m- /) are retracted by a probe (pr) to \'iew perforators (crossed arrows) and optic tract (ot) beh ind aneurysm (an) and bifurcation of carotid artery. pea, Posterior COIll-

113

municating artery; -UIIC. uncus; acha, anterior choroidal arte ry;s, suction lube; perf. perforators; 00, recurrem artery of Heubner;jl, frontal lobe; a-I, A-I artery; Ma. anterior com municating artery; it, lamina terminalis.

114

6. The Carotid Cislern and Environs

Fig. 6.19. Ano ther case with view of carOlid cistern and e nvirons, looking morc medially. Appearing deep between right internal carotid artery (r-iea) a nd o ptic apparatus a re seen perforators (peif). pituitary stalk (Pit), right posterior clinoid process (PC), lOp of lhe dorsum sellae (ds), le ft superior cerebellar artery (lsell), and left oculomotor nerve (3). Lateral to the right carotid artery 3rc noted the tentorial edge (te), side of the dorsum sellae (ds), a dural venous si nus

(us) behi nd the dorsum sellae, the posterior communicating artery (pea) and its adjacent aneurysm (crosud arrow), the P-2 artery (p.2). basilar artery (00),

and right oculomotor !len 'c (3). 2, Optic nerves; ch, o ptic chiasm ; 01, right o ptic tract;foo. right (bottom) and left (toP) fronto-orbital arteries;gr, right (bottom) and left (lOP) gyri recti; l-ita, med ial side of left internal carotid artery; a.-I, A- I artery_

Anatomy

Hg. 6.20. Same case as Fig. 6.19 emphasizing reo lationship of intcrnal ca rotid artcry (ica) and poster ior clinoid proccss (PC). Ids. Top of dorsum sellac covcrcd by dura ;fds, front of dOT5um seUae;sds. side of dOT5u m sellae; vs, vcnous sinus in dura beh ind dOT5u m sellae; J, oculomotor ncrve; col , cottonoids; P01lS, rostral pons; sea, right superior cerebellar arte ry behind 3rd ncrvc;p-2. PÂˇ2 artcry in front of3rd

115

ne rve; une, uncus;a1l. second aneurysm at takeoff of anterior choroidal a rlery (hidden); CTossed arrow, first aneurysm at takeoff of posterior communicating artc ry (hidden); rtf, r ight temporal lobe retractor; mÂˇ J, M- I a rte ry origin; 00, basilar artery ; Iry, hypophyseal perforator from ica; a- I , A- I a rte ry; 01, optic tract. Note Icft lateral medu llary pe rfo rator from basilar ;lrtCI,), a nd in shadows behind dorsum sellae.

6. The Carotid Cistern and Environs

116

,., Fig. 6.21. Ano ther case illu.n rating sympathetic fiÂˇ bers (5)'"') o n internal carotid artery (ica). ar (]alen]), Arachnoid band ; Ie, tcnlorial edge; an, aneurys m at takeoff of [.N)Sterior communicating artery (hidden: most of aneurysm is below lcnloriu m);cot, cottonoid:

frontal lobe rclrdctQr; ar (medial), arachnoid membrane between optic nerves; 2, right optic ncn'c; mem, membrane o f Liliequist; ac, anterior clino id process. From Fox [ I]. Il t,

Anatomy

Fig. 6.22. Another tase showing view of medial side of opposite (kfl) carotid cistern. reI, Retractor on right frontal lobe (fl); ch, optic chiasm; 2, both optic nerves; cot, cotton ball; clp, shank of aneurysm clip ; ac, right anterior clinoid process; ar, arachnoid fi-

117

bers; 1.5, tuberculum sellae; unc, medial side of left uneus;foa, left fronto-orbital artery on left fronta l lobe; m- I, origin ofleft M- I artery; v. vein ; ica, left internal carotid artery (medial side near bifurcation); a- I, origin ofleft A-I a rtery.

liS

6. The Carotid Cistern and Environs

Fig. 6.23. Another case with view of carotid and chiasmatic cisterns. The pituitary gland (pit) projects superior to the level of the diaph ragm sellae. Sing/to crossed arrow, portal veins o f pituitary stalk ; 2, optic nerves; ell, optic chiasm; r-ica, right internal carotid artery; hy, hypothalamic perforators from internal carotid artery; pc. dura of posterior clinoid process; mem omembrane o f Liliequist; v, unusual vein arising from cavernous sinus; double-crossed arrow, posterior

communicating artery; aella, one of two alllerior choroidal arteries;tl-ret, temporal lobe retractor; 111-1, M- l pordon of midd le cerebral artery; fmi, perforators from bifurcation of jea to alllcrior perforated substance; ot, right o ptic tract; a-I, A-I portion of anter ior cerebra 1 artery;fl-rel, fro mal lobe retractor; l-ica, left imernal carotid artery; l-pea, left posterior comm unicating artery. From Fox [2].

Anatomy

Fig. 6.24. Some case as Fig. 6.23. View is looking med ially toward the le ft internal Gl.rotid artery (i-ica). 2, Optic nerves; Pit, pituitary st.alk; l-pea, le ft posterior communicating artery; ch, optic ch iasm; a-1 , A- I portion of left anterior cerebral artery; cot, COtton strip;

119

1/j.-1, M-l portion of left middle cerebral artery;jl-ret, frontal lobe retractor; v, unusual vein on left arising from cavernous sinus; pr, probe retracting the vein ; crossed arrow, medial left temporallobc. ,"'rom Fox [2].

120

6. The Carotid Cistern and Environs

Fig. 6.25. Another case illustrating internal carotid artery (ita) and environs. pc, Posterior clinoid p rocess; an, giant aneurysm o f right PÂˇ1 artery; tl, right temporal lobe; mol, M-I artery; a-i, A-I artery; ret, retractor on frollla!lobe;a-2, right A-2 artery;gr, gyrus

rectus; am, anterior communicating arter y; 2, optic nerves; ch, optic chiasm; sha, superior hypophyseal artery; crossed arrow, one of several hypophyseal and anterior thalamic per forators in an arachnoid sheath; Qt, optic tract.

Anatomy

Fig. 6.26. Same case as Fig. 6.25. Probe (pr) is retracting right optic nenÂˇc (2) mcdially to show pituitary stalk (pit). pc, Posterior clinoid process; all. giant

121

ancurysm; te, telltorial edge; UIIC, uncus; ), oculomOlOr llen'c; I'll, temporal lobe retractor; bif, bifurcation of right internal carotid artery.

7- The Chiasmatic Cistern and Environs

Introduction

lamina terminalis is behind and above, and the olfac tory cisterns pass an terior to the chias-

As the surgeon d issects medially from the ptcriona l exposure, he or she enco unters a confl uence of cisterns in the ccn ter of which is the chiasmatic cistern . T he computed tomography (CT) scans with cerebral spinal fl uid (CSF) contrast e nhancement show the ch iasmatic cistern and adjacent cisterns (Figs. 7. 1 and 7.2). The ca rotid cisterns are lateral, the cistern of the

matic cistern. T h e o lfactory cistern lies between the gyrus rectus and medial orbital gyrus. I n the mid li ne between the fronta l lobes is the pericallosai cistern and interhemispheric fiss ure (cistern).

Fig. 7. 1. Axial \Âˇicw of CT scan after injection of iopamidol into the CSF by lu mbar pu ncture: cisternogram of chiasmatic cistern containing optic chiasm (black arrowhead) and medial poI-lions of optic nerve. Closed black arrow crosses ant.el-im-clinoid process and poi nts to lateral portion of optic nerve in carotid cistern; open arrow lies in confluence of upper

carotid cistern with med ial chiasmatic cistern from which arter ial shad ows of A-I (medially) and M-I (laterally) can be seen 10 originate; white arrow points to optic tract lying lateral to the laleral portion of the cistern o f the lamina terminalis and medial to the confluence of the two cisterns (carotid and sylvian); while triangle lies on lamina termi nalis.

124

7. The Chiasmatic Cistern and Enviro ns

Fig. 7.2. Coronal (fro mal) view of CT scan after injection o f iopamidol into the CSF by lumbar puncture: cistcrnogram of olfactory cistern. Black arruws lie in olfactory cistern and poim to olfaClory

branch of anterior cerebral artery in interhemispheric fiss ure; open arrow, contrast medium in subÂˇ arachnoid space (optic cistern) surrounding optic nerve in orbit.

tracts; while triangle, gy rus rectus; while dosed arrow,

Anatomy As the surgeon elevates the frontal lobe, the olfactory tract may be stretched if the brain is vcry relaxed . If thi s ha ppens, vei ns near the midline and traversing bcnveen the frontal lobe (gyrus rectus or adjace nt medial orbital gyrus) and nearby dural si nuses may lear and bleed . When such occurs, it will be necessary to expose the olfactory cistern (Figs. 7.3 and 7.4). This maneuver is not necessary unless bleeding occurs, requiring bipolar electrocoagulation of these veins. The olfactory tract appears as a white ba nd lying in the olfactory cistern. Posteriorly, it arises from the medial a nd lateral olfacto ry stria , formin g the from border of the anterior perforated substance. The tract is adherent to the fromallobc between the gyrus rectus (medially) and the medial orbital gyrus (laterally). further anteriorly the olfactory tract se parates from the brain (figs. 7.2 and 7.5) and passes toward the olfactory bu lb la teral to the crista galli (Fig. 7.6). From this olfactory bu lb pass the hidden fil a me nts of the olfactory nerves down through the cribiform plate and into the mucosa of the nose. As the dissection proceeds med ially from

the carotid cistern and into the chiasmatic cistern toward the anterior com municating complex, the surgeon may fo llow the A- I artery ifit is easily seen. Th is usually occurs if the inte rnal carotid artery is fairl y short. In cases where the inte rnal carotid a rtery is long a nd the A- I artery is hidden posteriorly, the surgeon shou ld avoid retraction of the frontal lobe to ex pose the A- I artery. If an anterior communicating artery aneurysm is the target. the approach is then directl y through the gyrus rectus [2-4]. T he la ndmarks for the I-cm incision in the gyrus rectus are illustrated in Figs. 7.7 and 7.8. The triangular or quadrangular zone inferior and lateral to the franta-orbita l artery lying on the gyrus rectus is described in the legends for these figures. If the sylvian fissure has been widely opened, elevation of the frontal lobe will brin g the optic chiasm, optic tract, and lamina terminalis (betwee n the optic tracts) into view in cases with a prefixed optic chiasm (ie, short optic nerves intracran ially). Figures 7.9and 7.10 a re two examples of a prefixed chiasm. The lam ina termina li s appears as a thin , translucent me mbrane retain ing third ventricular CS F inside. The CS F on its outer, visible side lies in the cistern of the lamina terminal is,

Anatomy which contains the medial portion of the A- I arteries, their interconnecting anterior communicating artery, and the recurrent artery of Heubner (Figs. 7.10-7. 12). The cistern of the lamina terminalis me rges with the chiasmatic cistern below and a nteriorly a nd with the interhe misphe ric fi ssure (cistern) superiorly. Laterally, the cistern of the lamina terminalis me rges with the confluence of the sylvian a nd carotid ciste rns lateral to the optic tract. Figures 7.13 and 7.14 are intraoperative photographs of the same patient. In I-igure 7.13 we see through the right carotid cistern a nd the lamina terminal is and ch iasmatic cisterns into the left (opposite) carotid cistern . The tented la mina tenninalis is prominent. The medial side of the left internal carotid a rtery is seen superior and inferior to the image of the left optic nerve. The left posterior communicating artery is visualized deep to the pituitary stalk. Pa nicularly important are the hypophyseal perforators from the carotid a rteries. If the A- I arteries are fo llowed medially and superiorly, the anterior communicating artery is seen lying in the cistern above a nd a nterior to the tented-up lamina terminalis (Fig. 7. 14). Figures 7.15 through 7. 18 are four exam ples of variations in the a natomy of the chiasmatic and lamina terminalis cisterns. In each case the inferoanterior zone of the lamina terminalis is visuali zed . In Figs. 7. 15 and 7. 16 the r ight late ral margin of the pituitary stal k is seen. This pituitary stalk, along wi th the optic nerves and chiasm, lies in the chiasmatic cistern (bounded caudally by the arachnoid membrane of Liliequist) . However, in many cases the me mbrane of Liliequist, which lies caudal to the pituitary stalk, sends an ante rior reflection of arachnoid membrane in front of the pituitary stalk. This situation puts the pituitary stalk inside its own hypophyseal cistern (Fig. 7.16). In l'ig. 7.16 note that the frontal lobe retraction is stretching arachnoid bands at the lateral margin of the cistem of the lamina terminalis. Figu res 7.17 and 7.18 add itionally illustrate the many variations in the pathway of the recurrent a rtery of He ubner. Generall y, this artery a rises from the A-I a rtery or the A-2 arte ry near the a nterior communicating artery (refer to Fig. 7.40). There may be two arteries of Heubner on one side. The artery passes later+ ally and lies superior to and behind or in fron t of the A-I and medial origi n of the M- ) arteries

125

and sends branches into the anterior perforated substance. Freque ntly the anery o f Heubner is seen before the A- I artery is iden+ tified, and it may bequite large (as in Fig. 7. 11 ). Figures 7.19 and 7.20 are photographs of the same patient before a nd after per foration of the lamina terminalis to treat hydrocephalus. One of the many variations in the anteriorcommunicating artery complex inside the lamina terminalis cistern is shown here. Such variations, with duplications and cross-bridges, are common (refer to Fig. 7.39). This is a triplicated anterior communicting artery complex with a bridge between two of the arteries. The artery of Heubner is well see n. Figures 7.2 1 through 7.24 de monstrate two patien ts in whom the artery of Heubner is the same diameter as the A- I artery (Figs. 7.21 and 7.22) or larger tha n the A- I artery (Figs. 7.23 and 7.24). In Fig. 7.21, the A- I artery is almost t... .:: size of an adjacent large M-I perforator, and the M- I arter y is equal in size to the internal cal"Otid artery. In Fig. 7.22 the pituitary stalk is surro unded by arachnoid (Liliequist's me mbrane beh ind and an a nterior reflection of the same me mbrane in front). He nce the pituita ry structures are 111 their own cistern (hypophyseal ciste rn). The same is true In another patient (Fig. 7.23) whe re part of the a nterior arachnoid enclosing this cistern has been opened by the surgeon . The pituitary stalk is redd ish due to the marked arterial and portal venous vascular+ ity (which partly accounts for its enhancement on CT scans with contrast medium). Figure 7.24 in the same patient shows a ve ry hypoplastic right A-I artery a nd a large right artery of Heu bn er. Additional anomalies are the low takeoff of the frontopolar arteries. The large left A- I artery supplies this unusual anterior commu nicating complex. Because the anterior communicating a rtery is lifted up by an a neurysm in the cistern of the lamina tel'minalis, descending "hypothalamic" perforato rs are well shown . Figure 7.25 is a n example of a patient with a prefixed chiasm and short internal carotid arteries. Without the surgeon go in g through the gyrus rectus, the right A- I, anterior commun icating, and left A- I arteries are seen upon elevation of the frontal lobe. Im ponan t perforators from the right A- I a rtery to the right optic tract, chiasm, and nerve are seen. I-igure 7.26 also is a photograph of a shon internal

7. The Ch iasmatic Cistern and Environs

126

Thble 7.1. Structu res contained within the chiasmatic cistern'. I. 2. 3. 4. 5. 6. i. 8. 9. 10.

Optic chiasm Optic ner\'es. medial border Surface of the gyrus rectus of the frontal lobe Tuberculum sellae (dural covering) Arachnoid membrane of Liliequist (Key and Retzills), rostral surface Arachnoid between optic neTl'es Superior hypophyseal artery Hypothalamic perforators A portion of the fronto-orbital artery Pituitary stalk (often lies within its own cistern)

Items 2-5 can be considered to form portions of the margins of the chiasmatic cistern.

Table 7.2. Structures contained ...Âˇithin the lamina terminalis cistern' . I. 2. 3. 4. 5. 6. 7. 8. 9. 10. II .

Outer surface of the lamina terminalis Surface of the optic tracts Surface oflhe gy rus rectus of the frontal lobe Anteriorcommunicatingartery Anterior cerebral artery, A-I portion Anterior cerebral artery, origin of A-2 portion Origin of the fronto-orbital artery Artery of Heubner, proximal portion Hypothalamic perforators from A-I and anterior communicatinganeries St.ria thalamic perforators from the A-I arte ry O rigin of an occasional accessory anterior cerebral artery

â&#x20AC;˘ Items 1-3 can be conside red to form portions of the margins of the lamina terminalis cistern.

carotid artery and a prefi xed chiasm . An unThe common ly duplicated a nterior comusual arterial anomaly is also illustrated: the ar- municating artery again is seen in Fig. 7. 33. Figtery of Heubner an d th e frolltopolar artery ure 7.34 shows the underside of a n anterior arise from a common trunk . This arterial com municati ng artery and nearby perforators. trunk origi nates at the right A- IIA-2 ar terial The optic tract is rarely well seen unless the junction. Branches from the ascend ing fron- sylvian fiss ure has been opened. Figures 7.35 topolar artery suppl y the territory of the ab- through 7.38 are examples ill ustrating this tract in two patients. I n fi gure 7.35 the origin sent franta-orbital a rtery. Figures 7.27 through 7. 30 reveal a common of an accessory anterior cerebral ar tery is seen variation in the amerior communica ting artery (someti mes mistaken for the base of an complex . In Figs. 7.27 through 7.29 the an- a ne urysm) . Figur e 7.36 (sa me patient) isa more terior communicating artery form s a "Y" with magnified view of the la mina terminalis seen one limb on the right a nd two limbs on the left. between a large artery o f Heubner and the A- I the superior one a nastomosing higher up on ane ry. A large ve in tur ns posteriorl y and passthe left A-2 artery. In Fig. 7.30 the an te rior es along with the optic tract to join the unseen com municati ng artery is duplicated ; the basilar vein of Rosenthal. superior one is hidde n by a layer of arachnoid . Figures 7.37 and 7.38 are twO views of the Figures 7.31 and 7.32 ill ustrate a nothe r right optic tract and chiasm. The A- I arteries example of a V-shaped anterior communicat- join the anterior communicating artery well ing arte ry with the common trunk on the right above the lamina terminalis, a nd the left A- I arand the two limbs on the lefl. Additionall y a tery has an unu sua l bridging artery retu rning large perforalor and an accessory ame rior back to the left A-I. Note the arachnoid band cerebral artery (a third, midline A-2 artery) (com pare with that in Fig. 7. 16) over the right arise at the division of this V-shaped anterior A-I artery at the lateral border of the cistern of communicating a rte ry. the lamina terminalis. Tables 7.1 and 7.2 sum-

127

AnalOmy

marize the various structures found in the chiasmatic and lamina terminalis cisterns. The duplications and bridges ofte n seen as the a nterior communicating artery complex were illustrated by Bremer [1] in 1943 (Fig. 7.39). But it was only with routine use of the operating microscope that surgeons saw how commonly such va riations occurred. Figure 7.40 is Westberg's representation of the usual course of the recu rrent artery of Heubner [5]. This large perforator sends branches illlo the anterior perforated substance along with the stria thalamic perforators from the A- I a nd M- l arteries.

Bibliography I. Bremer J L (1943) Congenital aneurysms of the

cerebral arteries. An embryologic study. Arch Pathol35: 819~83 1 2. Fox J L (1979) Microsurgical exposure of intracranial ane urysms. J Microsurg I : 2 - 31 3. Fox J L ( 1983) Intracranial Aneurysms, vol 2. New York , Springcr-Vcrlag, pp 877 - 1069 4. Kempe LG (1968) Operative Neurosurgery, vol I : Cranial, Cerebral, ami Intracranial Vascular Disease. New York, Springer-Verlag, pp 1- 75 5. Westberg G (1963) The recurrent artery of Heubne r and the arteries of the central ganglia. Acta Radiol (Diagn) 1: 949-954

7. The Chiasmatic Cistern and Environs

128

'0'

Fig. 7.3. Lower portion of olfactory tract (1). gr, Gyrus rcclus;2, right optic nerve;dura, dural margin of optic canal; ar, arachnoid covering internal

carotid artery (carotid cistern); ac, anterio r clinoid process; v, vein on temporallobe; s, Sliction lube; ret, retractor on fro ntal lobe.

Anatomy

Fig. 7.4. Same case as Fig. 7.3. Middle portion of right olfactory tract (1) in olfactory cistern. V, Vein in sulcus between frontal lobe (jT) and olfactory tract;

129

dura, dura covering orbital roof (floor of anterior fossa) projections; nt, retractor on frontal lobe.

130

7. The Chiasmatic Cistern and Environs

Fig. 7.5. Same case showing olfactory tract (1) passing through subarachnoid space from frontal lobe

(jl) toward cribi form plate and nose. v, Vein; a, artery;cg, dura of crista galli.

Anatomy

Fig. 7.6. Another case demonstrating olfactory bulb (ob) and upper olfactory tract (I). cg, Crista galli; ret,

131

retractor;jZ, base of frontal lobe ; dura, dura covering orbital roof projections.

132

7. The Chiasmatic Cistern and Environs

Fig. 7.7. Initial exposure of gyrus rectus (gr) during an approach to an amerior com municating artery aneurysm where the A-I artery is not followed medially. Note the quadrangular zone bounded by the edge of the frontal lobe retractor blade (jl-ret), the fTOlllo-orbital artery fjo), the frontallobe/optic nerve junction (dQuble-crossed arrow), and the olfactory tract

(/). T he incision in the gyrus rcelusis made here and the fronto-orbital artery is followed to the aneurysm. v, Vein; ar, arachnoid between optic nerves; 2, rigln optic nerve; ica, interna l carotid artery; Ie, anterior reflection of tentorial edge; Ii, temporallobc; II/em, membrane of Liliequisl; cot, cotton strip lying on sylvian fissure. From Fox [3].

AnaLOmy

Ag.7.8. Another case illustrating the initial exposure of gyrus rectus on the right (r-gr) where the right A-I anery (a-I, hottom) is fo llowed medially. Crossed arrow, interhe mispheric fissure. Note quadrangular zone oounded by the frontal lobe and right A-I j unction, the olfaclOry tract (/), the front.allobc retractor blade (jI-ret), an d the f!"OOlo-orbital artery I/o). The initial incision is made within this zone. r-gr, Right gyrus rectus; lIa, left artel-Y of Heubncr; i-gr,

133

medial surface of left gyrus rct:lus; i-10, left fronloorbital artery; aT, arach noid between optic nerves; 2, left and right optic nerves; Ii, temporallobc; ch, optic chiasm;it, lamina terminalis;o/, right optic tract;mca, branch of middle cerebral aner}, in sylvian fissure; a-l, left (toP) and right (hoI/om) A-I arteries converging lOward the hidden anlerior comm unicating arÂˇ ter y. From Fox [3J.

134

7. The Chiasmatic Cistern and Environs

Fig. 7.9. Another case illustrating prefixed optic chiasm (ch). Lamina terminalis (it) and its cistern beÂˇ tween the optic tracts (ot) arc seen. Within the cistern oftbe lami na terminalis is pari of the A- I anery(a- J) and a duplicated amerior communicating artery (aca). ar, Arachnoid between optic nerves (2); ica, internal carotid arte ry; ac, anterior dinoid process; pc,

posterio r clinoid process; ÂťMm, arachnoid membrane o f Liliequist; te, tentorial edge; ata, anterior temporal artery; It, temporal lobe; hij, bifurcation o f iea; tUmble-crossed arrow, origin of hidd en anterio r choroidal artery; single-crossed arrow, origin of hidden posterior com municating artery; /w., artery of Heubner.

Anatomy

135

Fig. 7.10. Another case with prefixed chiasm (ch) and short intracranial optic nerves (2). T he carotid, chiasmatic, and lamina terminalis cisterns appear here without identifiable boundaries after dissec·

tion. ica, Imernal carotid artery; Ii. temporal lobe; a·l, A·I artery; !Ia, artery of Heubner;j1, frontal lobe; 1$, tuberculum sellae; it, lamina terminalis; ot, optic tract. From Fox [2).

136

7. The Chiasmatic Cistern and Environs

Fig. 7.11. Same case as Fig. 7.10. A short imernal carotid artery has permitted exposure of the anterior communicating artery (aca) by followi ng the right A- I artery (a-I, bottom). The upper chiasmatic cistern and the cistern of the lamina tcrminalis are

exposed. ch, optic chiasm; It, lamina terminalis; ot, optic tract; ha, right (bottom) and left (toP) a rteries of Hcubner; gr, right gyrus rectus; a- J (lOP), left A-I arterYi/o, left [ront()-orbital artery on left gyrus reclus. From Fox [2 ] .

Anatomy

Fig. 7.12. Same case after removing about IÂˇem length of gyrus rectus to expose an anterior commun icating artery aneurysm (an) surrounded by left (lap) and riglll (bottom) A-2 arteries (a-2). Above are the left and below are the right A- I arteries (a-I), ar-

137

teries of Heubner (ha), and frorlLO-orbital arteries 1/0).//, Lamina lerminatis;gr, teft gyrus rectus. These st ructures lie within the lamina terminalis and interhem ispheric cisterns. From Fox [2].

138

7. The Chiasmatic Cistern and Environs

Fig. 7.13. Another case with exposure of all the anterior cisterns bounded by the left and right temporal lobes (l-Il, r-el). s, Suction tube above bifurcation ofleft internal carotid artery (l-ica); (1- 1, both A-I arteries; ii, lamina terminal is; ot, right optic tract;fl. right frontal lobe; 2 , both oplic nerves; ky. left and right hypophyseal perforators; Pit, pituitary stalk (and its hypophyseal cistern) surrounded by

arachnoid (ar), which splits and surrounds it; pc, posterior clinoid process; mem, me mbrane of Liliequist; l-ica and r-ica, both internal carotid arteries;l-pca and r-pea, both posterior communicating an eries. The left one (i-pea) lies in froOl of Liliequist membrane and is seen through the space between the pituitary stalk (pit) and [he right carotid artery (r-ica). From Fox [3].

139

Anatomy

-l Olf

fl-ret

(

Fig. 7.14. Same case after exposure ofrwo aneurysms on the anterior communicating artery. The small one projecting upward is obvious. The large one projects downward and is hidden by the anterior communicating artery (aca). Above and below arc the left and right A-I arteries (a-I) and A-2 arteries (an)

(a-2) . 111. left frontal lobe , Lt, lamina terminalis, 01,

right optic tract; bif, bifurcation of right internal carotid artery; col. couonoid; JUl, right artery of Heubner; fl-ret, right frontal lobe retractor. From Fox [3].

140

7. The Chiasmatic Cistern and Environs

Fig. 7. 15. Another case showing chiasmatic cistern both rostral and abo\'c (to observer's left) and caudal a nd behind (to observer's right) the optic ap pa ratus. $, Suction tube ; l-fl, left frontal lobe; ar, arach noid beÂˇ tween left oplie nerve and frontal lobe and separating left carotid cistern from chiasmatic cistern; 2. bolh optic nerves; fo, le ft fronto-orbi ta l ancl}'; ha, left arteries of Hcubnc r ; ell, optic chiasm; 01, right optic tract; ac, right anterior clinoid process; Pit,

pituitary gland projecting above (with rcspca to paliem) sella lUl'eica; ita, internal carmid artery; frs, pituita ry stalk; ft, la mina terminalis; rei, rctractoron right fro mal lobe; an, aneurysm arising from anterior commun icating artery; a-I and a-2, left (toP) and right (bol/om) A- I and A-2 artcrics:fp, low !.akrofr of le n frolHopolar artcr)' ;col, small coHon hall. From Fox [3}.

Anatomy

Fig. 7.16. Another case showing surgically induced communication between chiasmatic cistern rostrally and inter ped uncular cistern caudally. T he latler contains the basilar artery (ha) seen after opening the membrane of Liliequisl (mem). Note Liliequ ist's membrane sends an anterior reflection around pituitary sta lk (pit), thus enclosing the hypophyseal cistern. Double-crossed arrow, reflections of light from CS F in interped uncular cistern; ji"gle-crossed an-ow.

14 1

lies on short internal carotid artery and points 10 origin of posterior communicating artery; /l-ret, temporal lobe retracto r ; mÂˇ}, M- I artery; perf, largest of several perfo ratOrs from A-I artery (a-1); ot, right optic tract; ar, arachnoid bands at lateral margin of cistern of the lamina tenninalis; fl, lami na terminalis (covered by A- I artery);j1-rel, frontal lobe retractor; ell, optic chiasm; 2, both optic nerves; ac, anterior clinoid process. FrOIll Fox [2] .

142

7. The Chiasmatic Cistern and Environs

Fig. 7.17. Another example of structures in chiasmatÂˇ ic, carotid, and lamina lerminalis cisterns. 2, both optic nerves; ch, optic chiasm; ii, lamina terminalis; Q/, right o ptic tract; ac, aillerior clinoid process; d()Uble-cro5Sed arrow, origin of posterior communicating

artery from internal carotid artery;

)/1--/,

M-l artery;

perf, perforator from A-I artery (a-I); ha, artery of

Heubner;fo, franto-orbital artery; rei, retractor on frontallobe;sillgle-crossedarrow, interhem ispheric fissure; gr, left gyrus rectus.

Anatomy

Fig. 7.18. Another example of the lamina terminalis A bilobed anterior communicating artery ane urysm (an) is surrounded by the lert A-2 artery (a-2, loP), the anterior com municating artery (aca), and the rig ht A-2 artery (a-2, boltom). The termination of the lert A-I artery (a-I, toP) is seen. 2, both

(It).

143

optic nerves; ell, optic chiasm; ot, right optic tract; a-I (bottom), right A- I artery;ha, artery of Heubner; r-[o, r ight fronto-orbital artery;Jl, right frontal lobe; ret, retractors; V, vei n on lert gyrus rectus (gr); l-fo, left fronto-orbita l artery.

144

7. The Chiasmatic Cistern and Environs

Fig. 7,19. Another case illustrating lamina tcrminalis (ll), its cistern, and a variation of the anterior communicating complex with 3 arteries (uca) and a bridge (brl between 2 of them. a-I, Left (lOP) and r ight (bollom) A- I arteries; eh, optic chiasm; ot, righ t optic tract; single-crossed arrow, origin of posterior commu nicating artery: douhle-crrused arrow, origin of anterior choroidal artery; mol, M-I artery; v, vein; r-

JUl, rig ht artery of Hcubncr; ju,junction of anterior communicating artery and hiddell right A-2 artery; r-fo, right franto-orbital artery; an, microaneu rysm on anterior communicating artery; a-2, left A-2 artery; ar, arachnoid in interhemispheric fissure ; l-fo, left frollto-orbita.l artery; t-fla, Icrt artery of I-Ieubnc r. From Fox [3].

Anatomy

Fig. 7.20. Same case as Fig. 7. 19 after putting musli n (mu) on microaneurysm and open ing (singk-U05Std arrow) the lamina terminalis (It); ica, internal carotid

145

artery; doublt-cro.s.std arrow. anterior choroidal anery; nt, frontal lobe retractor; ot, optic tract;3v, third ventricle; tot, small cotton ball .

146

7. The Chiasmatic Cistern and Environs

Fig. 7.21. Chiasmatic cistern in case with hypoplastic right A-I artery (a-l). The recurrent artery of Hcubncr (ha) is as large as the A-I artery. p. Perforators; mol, M- I artery; m-2, fronta l (bottom) and temporal (top) M-2 arteries; aT, arachnoid over sylviall fissure; II, temporallobe;jl, frontal lobe; cot, cot-

tonoid; rei, fronta l lobe retractor; ft, lamina lcrminalis; ot, right optic tracl jch, opticchiasm;gr, right gyrus rectus; 2, both optic nen'es; l-ica, left internal carotid artcrYipit, pituitary stalk; mem, membrane of Liliequisl j T-ica, right internal carotid artery.

Anatomy

Fig. 7.22. Magnified view of Fig. 7.2 1. Arachnoid membrane of Liliequist (num) sends anterior sheet in fro nt of pituitary stalk (pit). ac, Anterior clinoid process; r-ica, atherosclerotic right internal carotid artery; cot, cottonoid; aM, anterior temporal anery from internal carotid artery; ret, temporal lobe re-

147

tractor; m-I, M-l artery; a-I, hypoplastic A-I artery;

p, perforator; IUl, artery of Heubner;foa, fromo-or-

bital anery; r-gr, right gyrus reClUS; ihf, interhemispheric fissure ; l-gr, left gyrus rectus; l-ica, left internal carotid anery; 2, both optic nerves; ch, optic chiasm; ft, lamina tenninalis; ot, right optic tract.

148

7. The Chiasmatic Cistern and Environs

Fig. 7.23. View of opposite imcrnai carotid cistern and ch iasmatic cistern. 2, both optic nerves; {-gr, left gyrus reclUs; i.oa, left ophthalmic artery going unde r left o ptic nerve; l-iea, atherosclerotic left internal carotid artery (medial sidc);is, tuberculum sellae; r-oo, origin of right ophthalmic artery; r-ica. right in-

lernal carotid artery; mem, part of membrane of Liliequisl (opened) passing in front of pituitary stalk (pit); p, hypothalamic perforator; ot, right optic tract; it, lam ina terminalisj ch. optic chiasm; ar, arachnoid between optic nerves. From Fox [3].

Anatomy

Fig. 7.24. Same case as Fig. 7.23 after removal of ,I small amount of right gyrus rectus (r-w) to view ciste rn of the lamina terminalis. Another example of a hypoplastic right A-I artery (a-I. !mllom) and a large right artery of Heubner (r-ha). The left A-2 artery is hidden by the right A-2 artery (a-2). an. Aneurysm projecting back against the lamina termi llalis (It); p. hypothalamic perforators stuck to alllerior COIl1-

149

1T1unicating ,1IÂˇtcry aneurysm; *, anterior communicating artery; r-/pa, right frontopolar artery (unusually low takeoff from the A-2 artery); I-[pa, left frontopolar artery; l-gr, left gyrus rectus;[oa, left fronto-orbital artery; I-ha, left artery of He ubner ; aI (loP), le ft A-I artery; 2, both o ptic nerves; ch, optic ch iasm; Pit, pituitatÂˇy stalk; ot, right optic tract. From Fox [3].

150

7. The Chiasmatic Cistern and Environs

Fig. 7.25. Example of chiasmatic cistern with prefixed oplic chiasm (short intracranial optic nerves). gel, Gelfoam on left optic nerve; 2, both optic nerves; ch, optic chiasm; iCG, internal carotid an ery; elp, shanks of two aneurysm dips; 01, oplic tract ; a-I,

right (bottom) and left (toP) A-I arteries; aca, anterior communicating artery; it, lamina terminalis; ha, right artery of Heubner; T-fl, right fronta l lobe; ihj, interhemispheric fissure (covered by arachnoid); l-fl, left f rontal lobe; l-foa, left fronta-orbital artery.

Anatomy

Fig. 7.26. Another case revealing an unusual common trunk (*) from which arise the right frontopolar artery (r-fpa) and the artery of Heubner (ha) . gr, Right gyrus rectus; a-2, right A-2 artery from which the above-mentioned trunk arises; l-fpa, left frontopolar artery; 2, left optic nerve; ch. optic chiasm;

151

a-I, left (toP) and right (bottom) A- I arteries; it, lamina terminalis; 01, optic tract; mem, membrane of Liliequist; ac, anterior clinoid process; ica, internal carotid artery; col, coltonoid. Note xanthochromic pigment (bilirubin) from hemoglobin of recent subarachnoid hemorrhage.

152

7. T he Chiasmatic Cistern and Environs

Fig. 7.27. Allother example where chiasmatic, carotid, and interpedu ncular cisterns arc all seen (from observer's left to right). 2, Both optic nerves; ch, optic ch iasm; 01, right optic tract; ito, internal carotid artery; single-crossed arrow, hidden o rigi n of poster ior com m u nicati ng artery; dQu.ble-crossed arrow,

hidden ongm of anterior choroidal artery; ac, anterior clinoid process; pc. posterior clinoid process; bo, basilar artery;3.ocu lomotor nerve; un, uncus; rei, fron tal lobe retractor; 00, artery of Heubner; a-I, right (bottom) and left (toP) A- I arteries_ See next two fi gures for anterior communicating artery complex .

Anatomy

Fig. 7.28. Same case as in Fig. 7.27. T}'pical variation in anterior communicating artery complex illustrated . a-I, Left (toP) and right (!mllom) A-I arleries; a-2, left (top) and right (bol/o.m) A-2 arleries; aea, anterior communicating arlcry; co, connecting bridge fro m anterior communicating arler}, to left A-2 ar-

153

tery; in!, arachnoid over interhemispher ic fissure;

lIa, arler}' of Heubner; ar, arachnoid fibers; iea, inter-

nal carotid artery; sillgle-crossed arrow, origin of posterior communicating artery; *, bifurcation of internal carotid artery.

154

7. T he Chiasmatic Cistern and Environs

fig. 7.29. Same case as in Figs. 7.27 and 7.28. Anterior com municating artery complex magnified . foa, Franto-orbital artery; ilif, arachnoid over interhemispheric fissure; a-2, left (toP) and right (bot10m) A-2 arteries; a-1, le ft (lOP) and right (hoI/om) A-I

arteries; Ma, anterior commun icating artery; co, connecti ng branch to the left A-2 artery; 2, both o ptic ne rves; ch, optic chiasm; ot, optic tract; 1m, artery of Heubner.

155

Anatomy

1' )

,.1 a-I

Fig. 7.30. Another case illustrating relationship of anterior communicating artery (aca) to chiasmatic and lamina terminalis cisterns. a- I , Left (toP) and right (bottom) A-I arteries; a-2 â&#x20AC;˘ left (lOP) and right (bot10m) A-2 arteries; 00, artery of 1ÂˇIl~ ubner and branches covered by arachnoid and blood ; ar, arach noid over interhemispheric fi ssure and cover-

ing a second anterior communicating artery; r-gr. right gyrus rectus; rtl, frontal lobe retraClOr; I, olfactory tract;jl, right frontallobe ;fpa, left frontopo lar artery (low takeoff); foa, left fronto-orbital artery; l-gr, left gyrus rectus; 2, both optic nerves; ts, tuberculum sellae; ch, optic chiasm; 01, right optic tract; It, lamina terminalis.

156

7. The Chiasmatic Cistern and Envil"Ons

Fig. 7.31. Another variation o f the anterior communicating artery comple x. From the anterior communicating artery (aca) arises both a connecting bridge (co) to the left A-2 (sec Fig. 7.32) and an accessory (third) anterior cerebral artery (ace) ascending between the two A-2 arteries. aÂˇÂˇ I , Left (toP) and right (bottQm) A- I arlc i-ies; a-2, left (lOP) and right (OOllom) A-2 arte ries; r-foa, right fronto-orbital artCl-Y; I, right

o lfactory tract; r-gr, right gyrus rectus; l-gr, left gyrus rectus; i-roa, left fronto-orbital artery; ar, arachnoid ; 2, both optic nerves; at, anterior clinoid p rocess; ica, internal carotid artery; *', bi furcation of the internal carotid artery (from wh ich unseen aneurysm arises); ot, right optic tract; cit, optic chiasm; It, lamina terminalis.

Anatomy

Fig. 7.32. 5."lme case as in Fig. 7.31 with right frontal lobe d isplaced by retractor (rei). a-1, Left (lOP) and right (hottom) A-I arteries; a-2, left (loP) and right (bot10m) A-2 arter ies; aca, anterior commu nicating artery; p, perforatOr; co, con necting branch fro m anterior communicating artery to the left A-2 artery; V, \'ei n; ace, accessory (third) anterior cerebral artery;

157

foa, left fronto-orbita l artery; I-JUl, left artery of Heubner; 2, right optic nen 'c; ac, right anter ior clinoid process; ch, optic chiasm (lateral side); ot, right optic tract; it. lamina terminalis; *, bifurcation of internal carotid artery from which arises base of aneurysm (an); m-2, M-2 artery; r-Iw, right a rte ry of Heubncr.

158

7. The Chiasmatic CiSlern and En"irons

Fig. 7.33. AnOlher case of anterior communicating artery (aca) duplication. a- I , Right A-I artery; M. artery of Heubner; 0-2, right (bottom) and left (top) A-2 arteries; Ttl, right frontal lobe retractor; ihf, interhemispheric fissure;gr, le ft gyrus rectus; I , left 01-

faclO ry tract; 2, both o ptic nerves; i-loa, left frollloorbital artery; an, aneurysm; Pit, pituitary stalk ; ica, internal carotid a rtery; ., bifurCllion of inlernai carotid artery; 01, right optic tract; ii, lamina terminalis; ch, optic chiasm; p. perforator.

Anatomy

Fig. 7.34. View of underside of an anterior com· municating artery complex in chiasmatic and lamina te rminalis cisterns. s, Suction tube; ua, internal carolid artery; ot, right optic tract; fI, lamina ter· minalis; p, hypothalamic perforators; a-J , right (001-

159

tom) and left (toP) A· I arteries; a-2, origin of left A-2 artery; (Ua, anterior communicating arte ry; ha, left artery of Heubner; 1-[00, left fronto-orbital artery; 1, left olfactol}' tract; 2, both optic nerves; ts, tuberculum sellae.

160

7. The Chiasmatic Cistern and Environs

Fig. 7.35. AnaLOmy o f lhe lamina terminalis and chiasmatic cisterns. 2, Both optic nerves; ar, vascular arach noid betweell optic nerves; cit, oplicch iasm;all,

aneurysm a rising from most of the internal carotid

artery; a-I, righ t (bottom) and left (lOP) A- I arteries; it,

lami na tcrminalis; JUI, artery of Heubner; ret, frontal lobe retrano}"; 0-2, right (boltom) and left (lOP) A-2 arteries; ace, origin o f accessory anterior cerebral artery; i/l[, arachnoid over interhemisphe ric fissure .

Anatomy

Fig. 7.36. Same case as in Fig. 7.35 with magnified viel\' of the lamina terminalis (It) between the right A-I artery (a-I) and artery of Heubner (ha). The lamina ter minalis is bordcred latcrally by the optic

161

tract (vi). Note arachnoid bands (or) and many PCI~ forating arteries (P). v, Vein: gr, gyrus reclus; all, aneurysm.

162

7. The Chiasmat ic Cistern and Environs

Fig, 7.37. Another exa mple of carotid, ch iasmatic, and lam ina tcnninalis ciSlCrnal analOmy. ica, intcrnal carotid artcry; Ie, edge of anterior reflection of tentori um ; pc. posterior clinoid proccss; /KO, posterior communicating artcry; oclw, anterior choroidal artcry; m-I, M-l ancr)'; QI, optic tract; (1"1, right (hollom) and Icft (loP) A- I arteries; dr, arachnoid

b<uld ; II, lamina lerminalis; dCd, anterior communicating artery; hr, bridging artcry from left A- I loanterior corn municati ngancry:Joo, left fronto-OI'bital artery; gr, left gyrus rectus; lUi, left anery of Heubner; eh, optic chiasm; 2, both optic ncn'CS; p, perforators.

Anatomy

Fig. 7.38. Same case as in Fig. 7.37, different view. iea, Internal carotid artery; pea, posterior com municating artery: aelta. anterior choroidal anery: mol, M- I arte ry; (I- I, right (bottom) and left (lOP) A- I arteries; P, perforator ; ill; arachnoid band; I路路IUI, right artery of Heubner and branches; r{oa . right fronLO-orbita l ar路

163

tery;a-2, origins of right (bottom ) and left (lOP) A-2 arteries; v, vein; aea, anterior communicating arter),; {100, left fronto-orbital artery;gr, left gyrus reclUS; 2, bOlh optic nerves; '路IUl, left artery of Heubner; 01, optic tract; fl, lamina tenninalis.

Fig. 7.39. A historic, diagrammatic example of an alllerior communicating arter ial complex form ing duplications and bridges. On ( ither side are the righ t and left A-IIA-2junctions. Fl"Om Bremer JL

Fig. 7.40. Photograph of a plastic cast (toP) and d iagram (bottom) o f the rec ur rent artery of Hcubncr as seen in front with two somewhat different p rojections. In the diagram the artery Heubncr is shown in 164

interrupted lines. From \Vcstbcrg C (1963) T he recurrent artery of Heubner and the ancrics of the central ganglia. Acta Radiol (Oiagn) I: 949-954 [5].

--8-The Ambient and Interpeduncular Cisterns

Jntroduction This cha pte r focuses on the pterional approach toward the ambien t and interpeduncula r cisterns. The surgical orientation of the patie nt's head (sec Fig. 4.8) is similar to that for the plerionai approach to the syivian, carotid , a nd chiasmatic cisterns . However, the o perating microscope is shifted from a more rostral d irection (see Fig. 4.5) to a mo re caudal line-of-

sight (see Fig. 4.7).

T he ambient cistern is a ce rebral spinal flui d (CS F) compartme nt made u p of the body and wing of the ambient cistern o n each side. T he body is borde red laterally by the medial surface of the te mporal lobe and the med ial ed ge of the te ntorial notch. It is borde red medially by the lateral surface of the midbrain a nd the pontomesencephalic junction. T he wing (not seen anato mically in this atJas) is a lateral extension of the body a nd lies betwecn the pul vinar of the thalam us anterio rly and the temporal lobe posterio rly. The bod y of the ambie nt cistern as seen in this atlas conta ins those structures following the tentorial edge and lying within the space between the carotid cistern rostra ll y and the inter peduncular cistern ca udall y. Some of these structu res (such as the a nte rior cho ro idal artery) arc assigned to a separate cru ral cistern by some authors [8}. T he basilar vein of Rosenthal a nd the terminus of the optic tract ca n be considered eithe r to lie within the ambient cistern or to make up pan of the med ial wall of the cistern . The third (oculo moto r) ne rve lies within both the interpeduncu lar cistern a nd the ambient cistern since the arachnoid membra ne of Lil iequ ist

(separating the rostral chiasmatic cistern from the caudal interpedu ncular ciste rn) usually is adherent along its lateral margin to the medial a nd caudal side o f the oculomo to r nerve. This me mbrane may sto p at or before the oculomotor nerve so that CS F in the interpedu ncular cistern mixes with CS F in the ambient cistern at a conflue nce lateral o r medial to the oculo motor nerve (Fig. 8.1; also sec Fig. 6.3). In some cases the Liliequist membrane ex te nd s la terall y to the tentorial ed ge (see Fig. 8. 10), a nd CS F fl ow must be through perforations in th is arach noid membra ne. T he posterior communicating artery and the P-2 portio n of the posterior cerebral artery as well as th e fourth (trochlea r) nerve and superior ce rebellar arter y also are partly within the body of the ambie nt cistern . Figure 8.2 shows the anatomy at the le,'el of the tentorial notch a nd midbrain . Figure 8.3 diagrams the anatomy of the auachmc nts of the tentorium ante riorly to the poste rior and a nterior clinoid processes. During the pteriOlla l a pproach to the inter peduncular cistern , the posterior cli noid process is an imponan t landmar k latera l to which is the oculomo to r nerve. Within the interpeduncular ciste rn lie the o rigins of the oculomoto r nerves, the tip of the basilar artery (Fig. 8.4), the origins of the P- I segments of the posterior cerebral arteries and the ir poste rior thala mic per forators (Fig. 8.4), and the origins of the superior cerebellar arte ries. I n the case of a shor t P- l artery, the caudal e nd of the poster ior communicating a rtery also may lie more medially a nd within the interped uncular cistem.

8. The Ambient and Interpeduncular Cisterns

166

Fig. 8.1. Diagram of sagittal sections of a normal brain and the sellar regio n , looki ng to the right. M, Mammillary body; LM, Lilicquist's mern branc(mcm bra ne of Key and Retzius); 3. right ocu lomOlOr Ilene; PC, right po~tc riol' clinoid process; DS, dorsum sellae; arrow, normal now o f CSF thro ugh the prepontine and interpeduncular cisterns. From ~ox J L, Al-~'Ie fty 0 (1980) Suprasellar arachnoid c)'s\s: an extension of the membrane of Liliequisl. Neurosurgery 7: 615 - 618 (4).

opt.< <hi""" 1 ,,{ u. ru\.. bulwn. Ne:rve. i-Bo.,ilor rut.,.~

5u.p

,,-,- 0,,"

lY NeT"" (m.b..."

p.duncl.

(.e:rt1.Cro..l

a:ftV"!:I

ou.du.c.t of

Qu.adriq.miMI

pio.t.

Fig. 8.2. Incisu ra of the te ntorium. The m idbrain was sectio ned transversely, and the he mispheres have been removed. Note relation of the bifurcation of the basilar artery to the environs in terms of a pIerÂˇ iOllal approach lO lhis region. From Taveras Jr-..[

(1960) T he roentgen diagnosis of intracranial incisura l space occupying lesions. Am J Roentgenol 84: 52-69 [7]. Copyright by American Roentgen R'ly SocielY. 1960.

Anatomy

167

Fig. 8.3. Relatio nship of posterior clinoid p rocess o n the left (A) and right (B) to the oculo motor nerve and circle o f Wil lis. Note relation ofposter iorclinoid process. posterior cOlllm un icating artery. 1'- 1 a rte ry, and oculo motor nerve t.o tip of basilar artery in terms of the pterio nal approach \0 the interped uncular ciste rn . Reprod uced by permission from Malkasian I) R. Rand RW ( 19i8) 1\'licrosurgical anatomy, in Ra nd R W (cd ): Microl1tllroslllgtry. cd ~ . St Louis, CV 1\losby Co, PI' 3i - iO [6]. A. Su perio r view view o f the le ft sellar and p,uasellar region de mo nstrating the d ural reneClions and the "oculomotor trigolle." /.ines wilh adjaunl OfN'11 arrOW.J. boundaries of the ocu lomotor trigone: .t, medial renections of the tentorium cerebclli : y.. posterior clinoid process; ~. anterior clinoid p rocess; d. d ia phragm sellae; laltra/ slmighl black arrow. ostium of the ilUernal carotid a rtc!)' : cw"Vtd (lITOU\ O\'c r o ptic nen'e and under falcifo rm ligamcnt;dolltd Ii/It. o pe ning to the o ptic foramcn; mtdial slmiglit arrow (black cMcurt'd), opening in d i:l ph ragm sellac fo r pituita ry stalk ; broke71 arr~ oculomotor ostium ; long black arrOW/lead, ostium of

the fou rth cranial ner\"c; l'lI/all black arrows. "Y" du ral fold. B. Su perior view of the sella illustrating the reo lationship o f the a n le rior clinoid process (11), midd le cerebr:11 art ery (C). poste rio r communicating arte ry U), oculo motor Ilc n e (fl, trochlear nerve (D), posÂˇ te rior ce rebral anery (C) and te ntorium cerebclli Illed i<l l renectio ll (1-:- /). Note that the oculo motOr ne rve is slightly lateral a nd inferior to the posterior commun icati ng an ery at the oculo motor ostium as it pe netrates the du ra in the oculomotor trigone. Howe\'er. as the oculomotor nerve P.1SseS inferior to the posterior communicating artery (prox imal to the midbrain), it may be im med iately inferior or slightly medial to the posterior cerebral artery-postcrior com municali ng artery ju nctio n. The anterior cho roid,ll artery has not been included . Unl1UJrked arrou~ falciform liga mell t o\"er the optic ne n 'c as it e nters the optic ca nal; E, frce edge o f the te ntorium cerebclli and its medial renection; H, basilar arte ry; I , posterior clinoid process; K. antc rio r cerebral artery.

168

8. T he Ambient and Interpeduncular Cisterns Fig. 8.4. Lateral vicw of vertebrohasilar arteriogram (subtraction technique) to show example of posterior thalamic pel-foratofs (arrow) arising from the pol artery and the basilar ancry bifurcation. From Fox [2]. ~

Fig. 8.5. Diagrams illustrating various relatio nships of the basilar artery termination to the dorsum sellae (A) and the th ird ventricle (B). From Greitz T, 1...Of5-

ted S (1954) The relationship between the third ventricle and the basilar artcry. Acta Radiol4 2: 85 - 100 [5].

169

Anatomy

Fig. 8.6. Two cxamplcsofiopamidol cislcrnography wilh axia l cr sections at lel·eI of midbrain. Thc cistcrnal CSF is whitc. A. UtIV)' black OrTout. from in· tcrhcmisphelic fissure to cistern of thc lamina lcr' millalis (poims to lamina tcrm inalis behind which is black unenhanced CSF in third ventricle): simigllt solid black OITOW lies at union of syl\'ian. chiasmatic and ambient cisterns and points to optic tract; wavy wllile aITow p<"lSses from lateral syl\'ian cistern (fissure) to medial sylvian cistem; jlmigllt solid wllile aITow lies on medial temporal lobc and points to the body of the ambient cistern lateral to midbrain : slum .wiid wllilt Qrrow lies on vcrm is of cercbellum and pOill lS 10 (illad rigc milial cistern : shorl o/lell Muck arrow lics in interpcdu ncular cistern and poims to mam-

millall' body of hYj>othalamus. B. BfackaITuwhead lics in j unction of ambient and intcrpedullcular cisterns and poillts 10 ocu lomotor nerve that separates these cisterns; doubit-headtd aITOW lies in interpeduncular cistcrn and points (a) anteriorly to pituitary stalk (surrounded by arachnoid enclosing less enhanccd CS F in hypophyscal cistern) and (b) posteriorly 10 ol1e of the two ascending P_I afleries;so/id black aITOW lies in intcrpeduncu la r cistcrn and extends from othcr asccnding P·l artery to postcrior clinoid process (whiter than tllC enhanced CSF);solid whitton'OW lies 011 peduncle of midbraill and points to body of ambient cistern ; opm arrow lies on anterior clinoid process aud points to internal carotid artery.

170

8. The Ambienl and In terpeduncular Cisterns

Within the interpeduncular cistern , the terminus of the basi lar artery may have various relationships with the dorsum sellae and its posterior clinoid processes as well as with the brainstem (Fi g. 8.5). The imaged anatomy of the structures about the ambie nt and interpeduncular cisterns can be see n in cross-section on the computed tomography (CT) scan after instillation of water-sol uble contrast medium into the CSF (Fig. 8.6). Figure 8.7 is a photograph of a plastic model of the brai n orie nted as the neurosurgeon will sec the brainstem, basilar a n e ry, superior cerebellar artery, oculomotor nerve, and poste rior cerebral a n e ry (P- I segment) . In Ihis view fro m the

plc riona l perspective, Lhe right temporal lobe and cerebellar hem isphere have been removed (a lso see Fig. 4.7).

Anatomy The surgeon follows th e posterior co mmunicating artery cau dally. Adhes ions between the uncus of the temporal lobe and oculomotor nerve are removed. The temporal lobe and its uncus are retracted. After openin g the a rachnoid membrane of Li licq uist (membrane of Key and Retzius), the surgeon sees the follow ing in a caudal-to-rostral direction (Figs. 8.8 and 8.9): the rostral pons, su perior cerebellar artery, oculomotor nen'e, posterior cerebral artery, posterior communicating a rtery a nd its anterior thalam ic perforators, a nI.erior choroidal artery. inl.ernal carotid artery. and optic nerve. The oculomotor nerve will be seen passing imo the dura of the oculomotor trigone (Fig. 8.3) just latera l to the posterior clinoid process. From there the oculomotor nen'e en ters the cavernous si nus. At this stage ofthe exposure, only the lateral termination of the P-I artery will be seen at its junction with the P-2 artery and the posterior communicating artery (Fig. 8.8). Usuall y the P- I artery is obscured by the a nterior thalam ic perforators as the artery curves ca udall y and medially away from the surgeon a nd lOward the basilar a rte ry tip. The upper trunk of the basilar a rtery may come into view (Fig. 8.9). At times the membrane of Liliequist will be thickened and imper fo rate from a previous

subarachnoid hemorrhage or me ningitis (Fig. 8.10), resulting in an obstruction to the fl ow of CSF a nd subsequent hydrocephalus. An incision in this thickened me mbrane (Fig. 8. 11 ) will result in a sudden flow of CSF a nd relaxation of the brain. Note thal now the a mel'ior thalamic perforators are seen on their lateral side whe reas views of the carotid cistern earlier showed these small arteries on their medial side (sec Figs. 6.7 and 6.8). In a rare patie nt the posterior clinoid process and its dural cover may project up between the caudal surfaces of the internal carotid artery and o ptic nerve or ch iasm (Fig. 8.1 2). In the majority of patients the posterior clinoid process projects upward in a parasagiual plane late ral to the in ternal carotid a rtery (Fig. 8.13). On occasion both posteriorclinoid processes and the top of the dorsum sel lae ca n be seen (Fig. 8. 14). This same figure shows the right posterior com municating artery clipped with small malleable clips (avoidi ng perforators) prior to severing this aner y between the cl ips. The PÂˇ2 artery passes laterally between the temporal lobe an d oculomotor nerve. The P- I artery takes its typical course away from the surgeon ; it loops superiorl y, caudally, a nd medially lOwa rd the rostral tip of the basi lar artery. In Fi g. 8.14 the midd le half of the P- I artery is hidden by the P-2 artery. Figure 8.15 is the sa me case after severin g of the right posterior communicating artery. Th is is a n unusual view of both P- I arteries, both 1'-2 arteries, and the left (opposite) posterior communicating a rtery. Figures 8.16 and 8. 17 a re two se parate examples of prev iolls su ba rachnoid hemorrhages that have caused adhesions in the arachnoid sheath enclosing the anterior thalamic perforators. T hese adhesions have ca used many of the perforators to stick together. This situation requires slow, del icate d issection to prevent perforator injury. Figures 8.18 and 8.19 are two se parate examples of approaches to the interped uncular cistern where the intracranial internal carotid artery is short. Re traction of the fronta l lobe brings A- I and M-I perforators into " iew at the bifurcation of the internal carotid artery. In Fig. 8. 18 the uncus, which hides the PÂˇ2 artery, is still ad herent to the oculomotor nerve. In Fig. 8. 19 the internal carotid artery hides the posterior communicating arte ry.

Anatomy

Fig. 8.7. Plastic model of brain: viewed as from a right pterional appro.1ch to the anatomy around the interpedu ncular cistern (see Figs. 4.6 and 4.i). The right temporal lobe and right cerebellum have been removed, btu the view is similar to that afte r wide opening of sylvian fiss ure. r-fl. Right front.allobe; J, both olf.lclory tracts; 1-1l, medial side of left (opposhe) temporal lobe; p-J, le ft Pol artery; i-sea, left supe rior cerebellar artery; ), right oculomotor lIerve; ba, b;:lsilar artery; '·va. left vertebral a rte ry: J~ va . rig ht I'enebral artery; //lcd, medulla oblo ngata ;

Iii

aiea, right anterior inferior cerebellar artery; 7 and 8. origins of facial and acoustic nerves; 6, right abd ucent nerve; 5. right trigeminal nerve arising from POllS: mep. sectioned middle cerebellar peduncle; ebllll, medial surface of le ft cerebellum (right side cut away); r-sea, right superior cerebellar artery; p·2, right 1'-2 ;1I·tel'}'; I'ed. pedu ncle (pyramidal tract) of midbrain: il'[. interpeduncular fossa of midbrain ; pea, right poste rior communicating artery; pil, pituitary bod y; 2. right optic nen'e; lIIam, mamillar}' bod y.

172

8. The Ambient and Imerpeduncular Cisterns

Figures 8.20 th rough 8.23 are examples of pending on the exaCl direction of the optics of the right latcral zone, middle zone, and left lal~ the microscope, the surgeon now sees both eral zone of the interpeduncular cistern as superior ce rebellar arteries (origins), both viewed progressively from the right pterional oculomoto r nerves, both P- I arte ries (origins), approach. In each res peClive case the micro- and the left mesence phalic peduncle (pyramiscope is tilted from a partial cauda-med ial di- daltract), T he anterior (frolltobasa l) surface of reclio n (ie, direction of the surgeon's view) to a the upper basilar a rtery is viewed by the surcaudal , yet morc medial, direction. Atthc same geon. time the righ t internal carOlid artery and the Figures 8.24 and 8.25 represent another proximal M- J artery arc displaced gently to the example of the transition from a view of the left (med iall y) by a llalTOW self-reta ining re- junClion of the a mbient and interped uncular tractor. Care is take n not to occlude the carotid cisterns (Fig. 8.24) to a view of the center of the artery (es pecially if vascular hypotension is interpeduncular cistern (Fig. 8,2 5), Note how used) or fracture atherosclerotic plaques in the the P-1 artery on the right tul"llS caudall y away a rtery. In some cases it may be necessary to clip fro m th e surgeon whi le the P- I artery on the (with sma ll malleable cli ps) and sever the post- left ta kes a more lateral course. Large and vital e rior com mu nicatin g artery (see Figs . 8.14 and ante rior a nd posterior thalamic perforators 8. 15), avoiding occlusion of anterior thalamic are presen l. pe rforato rs by the clips. Figure 8.26 gives a view of the anatomy of In Fig. 8.20 a clear view of the oculomotor the lamina termi nalis, chiasmatic, carotid , amnerve separating the superior cerebellar artery bient, a nd interpeduncular cistcl"Ils in one paand the P-2/posterior com municating junClion tient. Figme 8.27 demonstrates anatomy about is present. T his th ird cranial nerve begins, as it the carotid, ambient, and prepontine cistel"lls. typically does, as a broad neural band fro m the Figures 8.28 through 8.30 represent midbrain in the interpeduncular fo ssa. This another example of transi tion from viewing broad band gathers together rostral to the the lateral zone to viewing the central zone of pons and passed forward under the tentorial the interpeduncular cistern in a case of lowedge and into the oculomotor trigone (see lying basilar artery bifmcation. Figures 8.31 Fig. 8.3)just lateral to the posterior clinoid pro- through 8.33 il lustrate the ma ny anterior cess . The midbrain, from whence the thalamic perforators arising from the inte rnal oculomotor nerve originates, is hidden from carotid a nd posterior communicating arteries. view owing to the buckli ng of the brainstem They lie e nsheathed wi thin their own filmy during the e mbryonic stage of development. arachnoid envelope. Th e anter ior choroidal a rThe forward buckling of the developin g pon s tery takes a prominent course from the interaccounts fo r the rostral pons being seen by this nal carotid artery and' disappears behind the surgical ap proach. uncus. With retraction of the in temal carotid anery Figure 8.33 additionally gives a panoramic and a more medial til t of the aim of the micro- view of the anatomy of the lamina terminalis, scope, the center of the inter ped uncu lar cis- chiasmatic, carotid, ambient, and interpeduntern ca n be seen in Fig. 8.21. An even sharper cu lar cisterns. The relationshi p of th e posmedial angulation of the microscope aimed terior communicming artery to the P-I and P-2 caudal to the carotid a nery a nd hypothalamus arteries is illustra ted. Figure 8,34 gives a dear permits the surgeon to see beyond the inter- view from the bifurcation of the internal ped uncular midline as is revealed in Figs. 8.22 carotid a nd adjacent optic tract to the bifmcaa nd 8.23. In thi s circumstance the observer is tion of the basilar artery. The last two fi gures looking through the space between the back of dea rl y demonstrate that the pterional a pthe dorsum sellae and clivus (see Figs. 4.7 and proach permits access to lesions situatcd any8. 1) and the fron t of the brainstem (see where about the circle of Willis, It is ideally Fig. 8.7). With this right pterional approach , suited for multiple lesions (eg, aneurysms) prethe dorsum sellae (Fig. 8. 14) lies in the upper, sen t in diffcrent loci, yet within reach from the left-ha nd field of the observer's view, and the chiasmatic to the interpeduncular cisterns. basilar artery and rostral pons lie in the lower, The approach requi res sign ificant removal of right- hand field of the observer's view. De- the sphenoid wing and , in many cases, a wide

Anatomy

opening of the sylvian fissure. Add itional details of the neurosurgical techniques used by the author for lhis approach are given elsewhere [2].

Bibliography I. Fox J L (1979) f\I icrosurgical exposure of intracranial aneurysms.J Microsllrg I: 2-31 2. Fox J L (1983) Intracranial Ancwysms, vol 2. New York. SpringerÂˇVerlag, PP 877 - 1069 3. Fox JL (1985) Microsurgical exposure of venebrobasi lar aneurysms, in Rand RW (ed): Micra' neurosurgery, cd 3. St Louis, CV ]\'Iosby Co, PI' 589-599

173

4. "ox J L, AI-Mefty 0 (1980) Suprasellar arachnoid cysts: an extension of the membrane of Liliequisl. Neurosurgery 7: 615-618 5. Greilz T, Uifsled S (1954) The relationshi p between the third ventricle and the basilar anery. Acta Radiol42: 85 - 100 6. Malkasian DR, Rand RW (1978) Microsurgical anatomy, in Rand RW (ed): Micronfuroslllgcry,ed 2. St Louis, CV Mosbr Co, pp 37- 70 7. l avaras J M (1960) The roentgen diagnosis of inÂˇ cisural intracranial space occupring lesions. Am J Rocntgenol84: 52 - 69 8. Ya~rgil MG, Kasdaglis K, J ain KK el al (1976) Anatomical observations of the subarachnoid cisterns of the brai n during surgery. J Neurosurg 44: 298 - 302

174

8. The Ambient and Interpeduncular Cisterns

Fig. 8.8. Plcrional approach to ambient and interpedu ncular cisterns (see Fig. 8.7 and Fig. 4.7). pr, Probe retracting the illternal carotid artery (ica); 2, right o ptic nerve; ac, anterior clinoid process; aI', arachnoid: pc, posterior clinoid process; Ie , tentorial edge;), oculomotor ncn"c at lateral oordcr of interpedu ncular cistern and emering cavernous sinus th rough oculomotor ostium (see FIg. 8.3); sea, super"jol" cerebellar artery; col, cononoid: rei, tem-

\Xlra! lobe retractor; pons, rostral pan of pons; pea, posterior communicating anery entering posterior cerebral artery at the pol (P- / )/P-2(P-2) junction; p, anterior thalamic perforators; !lIIC, urlCUS: adw, duplicated anterior choroidal artery; v, \'cin. Note: P-2 artery and basal vein of Rosenthal lie ill ambient cistcrn between pontomesencephalic region and temporallobe. From Fox lll.

Anatomy

fi g. 8.9. Same case as in foig. 8.8. Probe (pr) isretrac ting posterio r commu nicating artc!"y (pea) to show origin of superio r cerebel lar a rtery (.sta) from basilar an ery (ha) in imcrpc duncula r cistcl"lI . m; Arach noid : porlS, rostral pa rt of pons; J, base of ocu lomo tor ne rve naring out at its midbra in origin: /1-/,1'-1 ar-

175

ter)'; p-2, 1>-2 arter), entcrin g ambien t cistern: Ii-rei, tempo ral lobe retracto r: ac}w, d u plicated anterio r choroidal artery ; Ime, uncus; V, vein : fl-rrt, frOlltal lobe rctractOl'; 2, optic nervc: iea, inte rnal carotid artcry:pc, posterio r clinoid process.

176

8. The Ambient and Interpeduncular Cisterns

Fig. 8.10. Path of posterior communicating anery (pea) in anothe r case. The thickened (horn previous subarachnoid bleed) arachnoid membrane of Liliequist (mem) separates unseen interpeduncu lar cistern from carotid cistern. The posterior communicating anery (pea) follows posterior extension of carotid cistern to join (*) the posterior cerebral artery (p-2) in the ambient cistern. The 1'-2 anery (P-2) ascends in the wing of the ambient cistern. ica,

Internal carotid artery; at, alllerio r clinoid process; tentorial margin: 3, oculomotor nerve; /l路rel, temporal lobe retractor; p, anterior thala mic perforators; ar, arachnoid membrane e nsheathing posterior communicating artery and its perforators (p); rei, relractor displacing M路l artery and carotid ar路 lery bifurcation median),; a'/, ol'igill of A路] ,trtery; 2. right optic nerve; at, anterior clinoid process. From Fox [2].

Ie,

Anatomy

Fig. 8.11. Same case as in Fig. 8. 10. Membrane or Liliequist (mem) has been opened, revcaling intcrpeduncular cistern. ), Right oculomotor nen'e; p, lateral medullary perforators: bo, basilar artery; r-

177

sea, right superior cerebellar artery; p-2, P-2 artery; pea, posterior communicating artery; INd, medial side or lert (opposite) peduncle of midbrain. From Fox [2).

178

8. The Ambiem and Imerpeduncular Cisterns

Fig. 8.12. Another case illustrating an unusual presentation of the posteriordinoid process (PC) projecting up between o ptic nerve (2) and internal carolid artery (ica). gr, Gyrus rectus; a-J, A- I artery; v, vein;

unc, UIl CUS; J, ocu lomotor nerve; an, collapsed aneurysm at posterior communicating artery; clp, clip on aneurysm; Ile, anterio r clinoid process.

Anatomy

Fig. 8.13. Anothe r case with view through ca rotid cistern into interpeduncular cistern. m-l, t.ÂˇI- 1artery; a- l , A- I artery; ot, optic tract; p, hypothalamic and anterior thalamic perfor,llors; ch, opLic chiasm; 2, right optic nerve; ac, amerior clinoid process; ica, internal carotid arterY;CTossed arrow, origin of posterior

li9

communicating artery (pea); ac/uJ., anterior choroidal a rtery; pol, P_I arte ry; p-2, P-2 artery; 3, oculomotor nerve; br, branch from superior cerebellar artery (sea); PO/IJ, rostral pons; an, aneurysm of basilar artery (00) at origi n of superior cerebella r artery (sea); pe, posterior clinoid process;ds, lOp of dorsum sellae.

180

8. The Ambient and Interpeduncular Cisterns

IÂˇsea

Fig. 8.14. Same case as in Fig. 8.13, looking leftward

across interpeduncular cistern. fl. Frontallobc; ret, retractor on internal cal"Olid artery (ica) and its bifurcation; p, ilnterior thalamic perforators; 2, right optic nerve; ac, amcrior clinoid process; l-pc, left (op'

posite) posterior clinoid process; tis, LOp of dorsum sellae; pc. right posterior clinoid process; I-sea, left superior cerebcll,ll" artery; ped, medial side o f left

peduncle of midbr.aiu; 3, left and right oculomotor nerves; cmssed Ulnm', one of twO malleable clips on posterior communicating ancry (pea); b-Ul!. base o f bifurcation aneurysm of basilar anery (00); /1-1, right pol anery; /1-2, right P-2 artery; UIlC, uncus; If-ret, ternporallobe retractor; pons. rostral pons; an, dome o r aneurysm at hidden origin or I'ight supclÂˇiorcerebcl. lar artery (r-sea).

Anatomy

Fig. 8.15. Same case asin Figs. 8.13 and 8.14. showing posterior circle of Willis in interpeduncular cistern. 2, Right optic nerve; iea, internal carotid alÂˇtery; ae, anterior clinoid process; i-pea , left poster ior communicating anery: p-2, left and right P-2 arteries; p-I.leftand right 1'- 1 aneries ;J, left (labeled twice) and right oculomotor nerves: l-pc, left posterio r

lSI

clinoid process; r-pc, right posterior clinoid process; 00, tip o f basilar artery; an, aneurysm at bifu rcation of hasilar artery; p, posterior thalamic perforators; ped, medial side of left peduncle of midbrain; sea, right superior cerebellar artery: pons. rostral pons; crossed arr~ malleable clip on caudal end of severed right posterior communicating artery; !Inc, uncus.

182

8. The Ambient and Inter peduncular Cisterns

Fig.8.16. Anothe r case illustrating the posterior comm unicating artery (pea) and its amerior thalamic perforators (p) stuck together by adhesions from previous hemorrhage. WIC, Uncus; aeM, anterior

choroidal artery; mol, M-I artery; pr, probe retracting internal carOlid artery (ica); a-I, A-I artery; 2, optic ne rve; pc, posterior clinoid process; mem, thickened membrane of Liliequist;;, ocu lomotor nene.

AnalOmy

Fig. 8.17. Anothcr case wherc the amerior thalamic perforalOrs (p) are stuck IOgether by adhesions in their cnclosing arach noid sheath. pr, Probe retracting intcrnal carotid artcry (ita); acha, duplicated anÂˇ terior choroidal artery and perforators ; crossed arrow, origi n of antcriorchoroidal aner),jan, aneurysms at

183

origin antcrior choroidal artcry (bottom) and posÂˇ terior communicating artery (toP): 2, optic ncn'c; boo, bifurcation of basilar artcry: 00, trunk of basilar artcry;), oculomotor ncrve;sca, superior ccrcbellar artcr),; p-2, P-2 an ery; pol, P_I artcry; pea, posterior comm unicating artcry; !II", uncus.

184

8. T he Ambient and Interpeduncular Cisterns

col

" I

Fig. 8.18. Following posterior comm u nicating artery (pea) toward interped uncular cistern hidden behind membrane of Liliequisl (mem). col, Coltonoicl; rei, temporal lobe retraCLQr; J, oculomotor nerve; unc,

uncus;p, anterior thalamic perforators and A-I perforators; akl, anterior temporal artery; mol, M-l af-

tery; a-I, A-I artery; 2, optic nerve; aeM, atHerior choroidal artery; ica, internal carotid artery; crossed arrow, origin of posterior communicating artery (pea); all, aneurysm at origin of posterior communicating artery; It, tentorial margin;pc, posterior clinoid process.

Anatomy

185

II-ret

Fig. 8.19. View ofrightlatcraJportion ofintcrpcduncular cistern after opening membrane of LiliequisL jl-rtl. Frontal lobe retractor; p, perforators from bi fu rcation of internal carotid artery (iea); 01, optic tract; a- I, A- I artery; mem, med ial jX>rtion of membrane of Liliequist; pc, posterior clinoid process; 00,

basi lar artery; an, aneurysm of basilar artery at origin of superior cerebellar artery (sea); p-l, P_I artery; p-2, P-2 artery; m-J, M-l artery; m-2, M-2 artery; It-nl, temjX>ral lobe retractor; unc, uncus; 3, ocu lomotor nerve; fe, tentor ial margin.

186

8. The Ambient and Intt:rpWuncular Cisterns

Fig. 8.20. Another case with view of right lateral portion o f interpeduncu lar cistern after remm'al of mcmbr.mc of Liliequisl. Notc how oculomotor nerve (J) gathers together from a broad band exiting the midbrain. pons. Rostral pons; sea, su perior cerebellar artery; 00, basilar artery near its bifu rcation: Ie, margin of te ntori um; /1, temporal lobe; col, cotlOno id ; rei, retractor: p-2, PÂˇ2 artery; p, perforators; 111-2. M-2 artery : mol, M- l artery; ot, optic tract; a-I.

A-I artery; 2, optic ne rve; mem, membrane of Liliequisl (anterior re n ectioll around pituitary stalk); ial, internal carotid artery; pea, posterior communicating artery; aciUl, anterior choroidal artery; pol, P_I artery. Reproduced by permission from Fox JL ( 1985) Microsurgical exposure ofvertebrobasilar aneurysms, in Rand RW (cd): MicrmleUrQS1I1gery, cd 3. Sf Louis, CV Mosby Co, pp 589-599 [3].

Anatomy

Fig. 8.21 . Same case as in Fig. 8.20. Internal carotid artery (ica ), middle cerebral artery (m-I), and posteriorcomm unicating artery (pea) retracted med ially by na rrow retractor (rtt ) to expose ceme r o r imerped uncu la r cistern contai ning aneurysm (an) at bi rurcation or basilar artery (ba). Except at its base, aneurysm is covcred by a carpet or fi brin. p-I. Left (loP) and rig ht (bottom) P- l arteries;sca, right su perior cerebellar a rtery: Ie, margin or tentorium : J,

187

oculomOlOr nen'C; pons. rostral pons; p. one o r several anterior thalamic perrorators rrom postcrior com municaling art.ery; 2. optic nerve; /le, anterior clinoid process:pc, posterior clinoid process. Reprod uced by permission rrom Fox J L (1985) Microneurosu rgical exposure or vertebrobasilar ane urysms. in Ra nd RW (cd): M icrotll'UfOsmgery,ed 3. 51 Lou is. CV Mosby Co, pp 589 - 599 [3).

188

8. The Ambient and Interpeduncular Cisterns

cot

Fig. 8.22. Example of ventral surface of basilar arlcry (ha) in interpeduncu lar cistern flanked by oculomotor nerves (3) . The membrane of Liliequist has been removed. t-sea, Left superior cerebellar aftef),; r-sea, right superior cerebellar artery; ], right and left oculomotor nerves; lie, right posterior clinoid process; pol, left and right P-l arteries; I),

posterior thalamic perforators from pol; *, base of basilar tip aneurysm; ica, internal carotid artery; ret, rClraClOr displacing iea bifurcation medially; aelia, anterior choroidal artery; fl. frontal lobe; col, cottonoid; /l-ret, right temporal lobe re tractor; crossed arrow, malleable dip on caudal end of severed right posterior communicating artery. From Fox [2J.

Anatomy

Fig. 8.23'. Another example of ventral surface of bifurcafion oflhe basilar artery (bba) in Ililerpeduncular cistern between both oculomotor nerves (3). prd, Left (opposite) peduncle (pyramidal tract) of mid brain ;sca. lcft superior cerebellar artery ; bo. basi-

189

iiiI' artery; Ie, margin oftentorium;p-l, right and left pol arteries; all, base of aneurysm at tip of basilar artery; fl-rel, frontal lobe retractor; Col, cottonoids; 11rtt, temporal lobe retractor. From Fox [2].

8. The Ambient and Interpeduncular Cisterns

190

,.1 '01

Fig. 8.24. Another case illustrating anatomy at j unction o f carotid , interpeduncular, and ambient cisterns after removal of arachnoid membrane of Lilicquist. rei, Retractor displacing internal carotid arte l")' medially; CQl, cou onoids; p, perforators; mol, M- I artery;aw, duplicated anter ior temporal artery;

v, veins; pons, rostral pons;), oculomotor nerve;sco, superior cerebellar artery; 00, basilar artery; pea, posterior communicating artery in carotid cistern; p-2, P-2 artery emering wing of ambient cistern beÂˇ tween pons and lemporallobe;p-J, pol artery going medially in interpeduncular cistern. From Fox [2J.

Ana{Qmy

191

". co.

r )

Fig. 8.25. Same case as in Fig. 8.24. View of ventral aspect of bifurcation of basilar artery (boo) and interÂˇ peduncular cistern between oculomO{Qr nerves (3). 00, Basilar artery: sea. right superior cerebellar artery; p-l, right (labeled twice) and lef! P_I arteries; p2, right P-2 arter y; pons, rostral pons; v, veins; ala, an-

terior temporal artery; mol. M-I artery; col, (ot{Qnoid; rel, retra({Qr on ica; p, posterior thalamic perforators; i-sea, left superior cerebellar artery; an, aneurysm of tip of basilar artery;crossed arrow, caudal end of severed posterior commu nicating artery (with malleable dips on it). From Fox [2] .

192

8. The Ambient and Interpeduncular Cisterns

Fig. 8.26. Another example of anatomy at confluence of carotid. lllle rpeduncular, and ambiem cislerns. cau-an, Dura of cavernous si nus containing giant internal carotid artery aneurysm; ica, internal carotid artery exiting from C3\'CrnOUS sinus; 00, basilar ancry; $la, superior cerebellar artery: J, OCU lO ll1 010 l' nerve entering cavernous sinus; pmlJ,

rostral pons; p-2. P-2 artery; crossed arrow points to posterior communicating artery hidden by internal carotid artery; unc, uncus; p. anterior thalamic perforalOr ; acha, anterior choroidal artery; *, bifurcation of internal carotid artery; col, cOllOnoids; fl, froma l lobc; QI, right optic tract; II, lamina terminalis; eli, o ptic chiasm; 2. both optic ne rves. t'rom Fox [2).

193

Anatomy

1I".t

00'

fig. 8.27. A vicw through carotid a nd interpeduncular cistel'lls into prepoilline cistern anterior to the pons (PO"s). ll路rtt , Temporal lobe retractor; col, cot路 tonoid; fl路ret, fro ntal lobe retractor; clp. shank of aneurysm clip on an 3mcriorcommunicating a rte ry ancurysm; a路 l. A- I artcry; mol . M-l an ery; tmc,

uncus; sea, superior cerebellar anery; an, a neurysm of basilar arte ry (1M) at takeoff of amerior inferior cerebellar anery ; J, oculomotor nerve; pc. posterior cli noid process; ica. internal carotid artery. From Fox [2].

194

8. The Ambicni and Jnterpeduncular Cisterns

Fig. 8.28. Another case with view of carotid , interpeduncula r, and rostral prepontine cisterns. Ie, Ma rgin o f te ntorium ; mem, remainde r of membrane o f Lilicquisl (most removed): rti, temporal lobe retraeLOr ; pons, rostral pons; J, oculomotor ncn'c;jK. post-

crior clinoid process; ac, anterior clinoid process; ica, jlllcrnal carotid artery; 2, o ptic nCl've; QI. optic tract; a-I, A- I artery; m-l, M-I artery; p-2, P-2 artery;p- J. p. I artery; crossed arrou, origin of posterior communicating artery.

Anatomy

fig. 8.29. Same case as in ~ig. 8.28 with medial retraction (1"(/) of the internal carotid artery (ica). 2. Optic ne rve: ac, anterior clinoid process; pc, posterior clinoid process;pÂˇl, left (obscured with blood) and right P- J arteries; " bifurcation of basilar artery; an, aneurysm of b.1silar artery at takeoff of hidden

195

right su pcrior cerebella r artery; ), oculomotOr nen'e entering cavernous sinus; POtU, rostral pons; p, perforator; p-2, right P-2 artery: pea, posterior communicating artel")'; m-l, MÂˇJ artel")'; 0-1, A- I artery; 01, optic tract.

196

8. The Ambient and Interpeduncular Cisterns

Fig. 8.30. Same case as in Figs. 8.28 and 8.29. View of bifurcation of basilar artery (boo) in center of imerpeduncular cistern. pol, Left and right po l arteries; J, ocu lo motor ncn"c; all, aneurysm at o rigi n of

superior cerebellar artery (sea); Ie, margin of tenLOriu m; pons. rostral pons; *, bifurcation of imernal carotid artery; ret, retractor displacing imernal carotid artery medially.

AnatOmy

Fig. 8.3 1. Another case, following arachnoid sheath of posterior communicating artery (pea) and iL" anÂˇ terior thalamic pe rforators (I) caudally toward inlerpeduncular cistern hidden behind membranc o f Lilic(IUist (mem). Ie, f\hrgin ofte nlOriull1 : ulle. uncus; IfÂˇrel, temporal lobe retractor: fl, fronta l lobe; PI', probe rctracting M-I artery (m-I) medially; 01, o ptic

197

tracl;jl-J'et, frontal lobe retractor; a-I, A-I artery; fl, lamina te n ninalis; cit, optic chiasm; iea, internal carotid artery: 011, aneurysm at origin o f posterior communicafing artcry; Gclla, amcrior choroidal artery passing under uncus toward choroid fissurc of lClllporallobe.

198

8. The Ambient and Interpeduncular Cisterns

Fig. 8.32. Same case as in Fig. 8.31 at higher magnificatio n to show anterior thalamic perforators (p) from postcfiorcommunicating artery (pea) and thei r ensheathi ng a rachnoid. ar, Thickened arachnoid

bands within envelope of arachnoid about perforators and posterior communicating artery; un" uncus of right tern poral lobe; adm , anterior choroidal artery; ica, interna l carotid artery; QI , o ptic tract.

AnalOmy

Fig.8.33. Same case as in Figs. 8.3 1 and 8.32. Arach noid membrane of Liliequ ist has becn dissected away. Note how pterional approach can gi\Âˇc panoramic vicw of chiasmatic, lamina terminalis, carotid, ambielll, and interpeduncular cisterns. 2, Both optic nerves; eh, optic chiasm; It. lamina termi nalis; 01, right optic tract; a.-I, A-I artery; p, per-

199

forators ; m-J, M-l artery; m-2, M-2 artery; ar, arachnoid sheath; aeM, anterior choroidal artery; ita, internal carotid artery; an, aneurysm; pea, posterior communicating artery; 00, basilar artery; p- l , P-I artery; p-2, P-2 a rte ry:), oculomotor nerve ; sea, origin of right superior cerebellar artery.

200

8. T he Ambient and Interpeduncular Cisterns

Fig. 8.34. Another case illustrating bifurcation of basilar artery (boo) in interpeduncular cistern. I-sea, Left superior cerebellar artery; pc. posterior clinoid process; ), left (h idden in shadows) and right oculomotor nerves; v, vein; r-sea, or igin of right superior cerebellar artery; {1-J, right and le ft pol ar-

teries in interped uncular cistern; pea, posterior communicating artery; p-2, origin of right PÂˇ2 artery; p, perforators; Il-ret, temporal lobe retractor ; unc, uncus; mol, r.1- 1 artery; ot, optic tran; ha, artery of Heubncr;jl, frontal lobe; a-I, A- I artery; aCM, anterior choroidal artery; ica, internal carotid artery.

Index

A Abducens nerve, 171 Acoustic nerve, origi n of, 17 1 Adhesions arachnoid membra ne, 94 between fro ntal and te mporal lobes. 56, 71 carotid arlery aneurysm to ocu lomoto r nerve, 111 fron tal lobe to oplic tract, 10. Ambient ciste rn, 165-200 anatomy of, 172, 199 body of, 169 j unction with ca rotid and interpeduncular ciste rns. 169, 172, 190, 192 j unction wi th sylvian and chiasmatic cisterns, 169 Aneurys m anterior cere bral artery A- I, 92, 16 1 anle rior choroidal artery. 92. 108 at o rigin, 84, 115, 183 anterior communicating arÂˇ lery, 124 , 132, 137, 139, 140, 143- 144, 193 hypothalamic perfo rators stuck to, 125, 149 basilar artery_ Stt Basilar aftery. aneurys m o f internal carotid artery. See Carotid artery, internal, a neurysm of middle cerebral arte ry M- I al bifurcation, 76-77 d ome in temporal lobe, 75 fl anked by tem poral and fro ntal M-2 arte ries, 7879

posterior cerebral an ery P- I, 120 posterior commun icati ng arÂˇ tery, 11 4. 178 at o rigin. 11 5- 11 6, 183184,197 at superio r cerebellar artery origin , 180. 185, 196 Aqueduct of Sylvius, 166 Arachnoid , 156, 174- 175 anterior re fl ection at pituitary sta lk, 125, 186 between frontal and tem poral lobes, 72 sc\'e red by microscissors, 56,84 between left optic nerve and frolltallobe. 140 between optic nerves, 98-99. 102, 116, 132-134, 148, 160 coveri ng inte rnal carotid artery and o ptic ne rve, 53, 74 d iste nded by cerebrospinal fl uid , 56. 59 at inte rhemispheric fissu re, 144, 150, 153-155, 160 at pituitary stalk, 138, 169 surgica l opelling of, 57, 8788, 177 and sepa ration by fo rceps blades, 64-65, 67 at sylvia n fissure. 146 Arachnoid bands o r fibers, 57, 87.90-91, 11 7. 153 at anterior cerebral artery A- I, 84, 127, 16 1- 163 in arachnoid envelope of thalamic perfo rators and posterio r communicating

artery. 198 between hypothalamic perforators and o ptic tract, 81 between midd le cerebral arte ry branches, 56, 70-

73 between middle cerebral M- l artery and temporal lobe. 80 between sylvia n vessels and pia, 63 at illlernal carotid artery, 67. 11 6 at lamina terminalis cistern , 125.14 1 at o ptic nerve/carotid a rtery j u nctio n, 67 at posterio r communicating artery, 83 in subd ura l space, 56, 58, 60-6 1 at sylvian fissure base. 56, 65-66 Arachnoid membrane of Liliequist, 68-69, 93-94, 98100, 103- 104. 107, 111 112, 116. 11 8. 125, 134, 138, 141 , 146- 148, 15 1, 165- 166, 184 adhesions o f, 94 attachme nts of, 98 coloratio n o f. 97 medial portion of, 185 at pituita ry stalk, 125, 138. 147- 148, 186 reflection of, 98 removal of, 188 surgical opening o f. 177 th ickening after he morrhage. 170, 176, 182

202

Index

Arachno id sheath of posterior communicating artery. 176 o f thalam ic perforators, 120 from posterior communicating an ery. 172, 197-

198

B Basilar ane ry. 39, 44-45, 69, 84, 107, 114 , 152. 171 ,

177, 190,192,199 aneurysm of. 179 at anterior infe rior (erebelÂˇ lar artery takeoff. 193 at bifurcation, 82, 18018 1, 187 at superior cerebellar arteryorigin, 185, 195 at tip. 18S-189, 191 bifurcation of, 166. 168, 183, 195--196, 200 between oculomotor nerves, 19 1 medullary perforators from, 11 5 near bifurcation, 186 origin of superior cerebellar artery. 165. 175, 179 relation to dorsum sellae, 168 relation to third ventricle.

168

lip of, 165, 18 1 tru nk of. 183 ventral surface of at bi furcation, 189, 191 nan ked by ocu lomotor nerves, 188

Basilar vein of Rosenthal, 165, 174

Bone nap attached to temporalis muscle, 40, 49 frontotemporal, 39-40 sutures for reattachment of, 40, 49 Bone-removal instrume nts, 24 Bonewax, use of, 24 Bridging artery from anterior communicating artery to left A-I, 126, 162 to left A-2, 11 2, 126, 153154, 157 Bridging veins between temporal lobe and sphenoparietal sinus, 4 1, 56,

66,74 electrocoagulatio n of, 56, 68 BUTT holes, 40, 48, 50

C Carotid artery, internal, 52, 6 1, 65-66, 77, 91, 110- 112, 135, 140, 145, 150-153, 159, 162- 163, 166, 169, 174- 176, 179- 184,IS6ISS, 193- 195, 197- 198 aneurysm of, 89-90, 104, 160, 192, 199 ad hesion to ocu lomotor nerve, II I adhesion to temporal lobe,

100 adhesion to tentori um ,

101

at anterior cho roidal artery takeoff, 84 at bifurcation , 57,85. 112113, 121 , 156- 157 arachnoid bands on, 67 ,11 6 arachnoid co,"ering of, 53, 74 athe rosclerotic, 63, 80, 10 1102, 107, 147- 148 bifurcatwn of, 79, 81, 84, 134 , 153, 156- 158, 192. 196,200 branches of, 57, 79 exit from cavernous sinus,

192 lateral retraction of, 103 left, 106, 114, 117- 11 9, 138, 146-147 bifurcation of, 138 long, 95, 98--99, 102 medial retraction o f, 109 origi n of anterior choroidal artery, 95, 100, 104, 13'1, 144, 152, 183 origin of posterior communicating artery, 95, 98, 100-101 , 104-105, I I I, 134, 141-142, 144 , 152153, 179,184, 194 ostium of, 167 perforatOrs from , 11 3- 114 ,

158 to anterior perforated substance, 118 at bifurcation, 11 8, 185 hypo physeal, 95, 99, l iS, 120, 125, 138 hypothalamic, 8 1, 95, 102-

103, 106, 11 8, 148, 159,

179 thalamic, anterior, 95, 102- 103, 120,172, 179 relation to carotid cistern, 93 relation to posterior clinoid process, 96, 114- 115 unusual, 170, 178 relation to posterior communicating artery, 192 right, 106, 114 , l iS, 138, 146, 148 bifurcat ion of, 12 1, 139 short, 95, 100-10 I sympathetic fibers on , 96, 11 6 view 10 optic tract, 103 Carotid cistern , 93- 12 1, 123, 128, 14S, 152 analOmy of, 93-97, 162, 172, 199 exposure of, 52 j unction with ambient and interpeduncular cisterns, 172, 190, 192 structures in, 96 Cavernous sinus, 95, 98 internal carotid artery exit from , 192 oculomotor nerve in , 170,

174

e ntrance of, 192, 195 unusual veins in , 97, 11 8-- 119 Cerebellar artery. anterior inferior aneurysm at takeoff from basilar artery, 193 right, 171 Cerebellar artery, superior, 165, 166.170, 174 , 183, 190, 192- 193 aneurysm at origin o f, ISO, IS5, I96

branch of, 179 le ft , 114 , 17 1, ISO, 188-- 189, 191,200 origin from basilar artery, 165,175,179 rig ht, S2, li S, 17 1, 177, l SI, 187- ISS, 191 aneu rys m at takeoff from basilar artery, 195 origin of, 199,200 separated by oculomotor nerve, 186 Cerebellum, 166 middle peduncle of, 17 1

203

Index tentorium of. See Tentorium cerebelli vermis of, 169 Cerebral arteries, anterior, 124,

167 A- I artery, 77, 85, 91, 93- 94, 10 1, 11 0, 11 3- 115. 118, 120, 123, 124, 133-135, 178-179, 182, 193-195, 197, 199-200 aneurysm of, 92, 16 1 arachnoid band over, 84, 127, 161- 163 hypoplasia of, 125. 146147, 149 left, 11 9, 125, 126, 136140,143- 144,149- 157, 159- 160. 162- 163 bridging artery to anterIOr communicating artery, 127, 162 origi n of, 82-83. 100, 108. 11 7,176 perforators from, 57. 7980,82,84,92,106.141142, 161 - 163, 170, 184, 186, 199 relation to artery o f Heubner, 95 right. 125. 126, 136- 140, 143-144 , 150-163 j unction with right A-2,

11 2 transsylvian view of, 82-83 A-2 artery, 126, 156-157 and common tru nk for artery of Heubner and right fro ntopolar artery, 126, 15 1 left. 137. 139- 140, 144, 153- 158, 160 bridging artery from anterior communicating artery. 112, 126, 1 53~ 154, 157 origin of, 159. 163 rig ht, 120, 137. 139- 140, 143, 149. 153- 158, 160 j unctio n with anterior communicating artery, 144

ju nction with rig ht A- I ,

11 2 origin of, 163 accessory. 126, 156- 157 o rigin o f, 127. 160 in chiasmatic cistern, 55

Cerebral arteries, mid d le. 55 branches of, 56, 57,60,66, 70-71,75,86-90,133 M- I arte ry. 84-85, 93, 94, 118, 120, 123, 14 1- 142, 144, 162-163, 179,182, 193-195, 197, 199-200 aneurysm o f at bifurca tion, 76-77 dome in temporal lobe,

75 nan ked by temporal and frontal M-2 arteries, 78-79 deep in sylvian fissu re, 89 emering sylvian fissu re, 8 1 frontal artery from, 75, 89 left, 11 9 long, 67, 78 origin of, 82-83, 106, 108, 112- 11 3, 11 5, 117 perforators fro m, 57.798 1,89-92,125,1 46- 147, 170, 181, 184-187, 190191,200 short, 57, 79 transsylvian view of, 82-83 variations in, 57 , 75 M-2 artery, 83, 90,157, 185186,199 aneu rys ms at bi fu rcation at M- I.77 dee p branches of, 87 fronta l artery from, 61, 76, 80,88, 146 variations in, 57, 75 Cerebral arteries, posterior. 108-109, 166- 167 1'-1 artery, 175 , 179, 183, 185-186, 194 aneurysm of, 120 ascending. 169 course o f, 170, 172, 190 left, 17 1, 181, 187- 189, 191. 195-196,200 origi n o f. 165 perforators from, 165, 168, 181,188,195 right, 180- 18 1, 187-189, 191, 195-196,200 short, 165 P-2 artery, 109, 114-1 15, 165, 176- 177,179. 183, 185, 192. 194 course of. 170 entering ambient cistern, 175, 190

left, 18 1 perfo rators from, 186, 190--19 1 right, 171, 180- 18 1. 19 1, 195 origin of. 200 relatio n o f P- 1 and 1'-2 to posterior communicating artery. 170, 172, 174. 186,199 Cerebral peduncle, 166 Cerebrospinal fluid circulation of, 94 in d istension of arachnoid membrane, 56, 59 drainage by lu mbar puncture, 40-4 1 fl ow through interpedu ncular cistern, 165, 166 in midbrai n se<:tions, 169 Chair, surgeon's, 16 Chiasmatic cistern. 93, 123- 164 anatomy o f, 123- 127. 172, 199 structures in. 126 union with sylvian and ambient cisterns, 169 Cho roidal artery, anterior. 57. 77,80--82,85,9 1,107, 110, 112- 113, 11 8, 145, 162- 163, 179,182,184, 186, 188, 192. 198-200 aneurysm of, 92, 108 at origin , 84. 115, 183 cou rse of, 172. 197 duplicated, 174, 175, 183 origin of, 95, 100, 104, 134, 144, 152, 183 perforato rs from, 183 relation to uncus of te mporal lobe, 95, 105 Circle o f Willis posterior, 18 1 relation to posterior clinoid process, 167 Clinoid process of sphenoid

bon'

anterior, 37-38, 4 1-44. 5 1, 69,83, 100, 107- 108, 11 0- 11 2. 11 6- 11 7. 123. 128, 134,141-142, 147, 151-152. 156, 167, 169. 174, 176,178-18 1, 187, 194- 195 attach ment to tentorium,

165

rig ht, 140, 157

204 Clino id process (to'I/.) posterior, 37-38, 42-45, 6667 ,69,83,98,100, 106108, 110- 111 , lJ 8, [20121, 138,152, 162, 167, 169, 174-175, 179, 182, 184-185, 187, 193- 195, 200 at tachment to tCllloriutn, 165 dura on, 99, 102. 118 left, 170, 180-- 18 1 relation to internal carotid artery. 96, 114- 115 right, 114, 166, 170, 18018 1, 188 unusual presentation or. 170, 178 Com municating artery. anterior, 11 3. 120, 150, 159, 163 aneurysm of, 124, 132, 137, 139- 140, 14 3- 144 , 193 hypothalamic perforators stuck to, 125, 149

bridging artery from left A· I, 127, 162 bridging artery to left A-2. 112. 126, 153- 154, 157 duplicating, 126, 127, 134, ISS, 158. 164 ju nction with A·I and A-2 arteries, 112, 144 perforators from , 11 2, 157 triplicating complex of, 125, 144 variations in complex of, 126. 127, 153- 157 V-shaped. 126. 152- 154. 156-157 Communicating artery. poster· ior, 77, 85, 91, 99. 11 211 3, 162- 163. 175,177. 195, 200 adjacent aneurysm, 114 aneurysm of collapsed, 178 at origin , 115- 11 6, 183184, 197 in carotid cistern, 190 caudal end in interpeduncu· lar cistern, 165 clips on, 170, 178, 180- 18 1, 188, 191 course o f, 176 ensheathed by arachnoid membrane, [76

Index hidden by internal carolid artery, 192 junction with P· I and P·2 ar· teries, 170, 172, 174 , 186 lateral direction of, 95, 106107 left , 11 8- 119, 138 origin of. 95. 98.100-10 1, 104- 105.11 1. 134, 14 1142, 144,152- 153,179, 184,194 perforalOrs frOm hypoph yseal,95, 102 hypothalamic, 95. 102- 103 thalamic, anterior, 82-83, 95, 102- 103, 109- 110, 172.174,176, 180, 184, 187.190, 192, 197- 198 adhesions in arachnoid sheath of. 170. 182183 in arachnoid sheath . 198 preaneurysmaltype of infundibulum . 95. 1[0 relation to P· I and P-2 arteries, 170, 172. 174. 186, 199 right, 138, 17 1 small, 95, 108 Cranimomy, right frontolateral, 39 Cribriform plate, 124, 130 Crista ga lli, 124 , 130-13 1 Cushing, Ha rvey. 2, 3. 4

Dahlgren. Karl , 3 Dandy, Walter, 4, 5-6 De Martel, Thierry. 3-4 Diaphragm sellae, 106. 112, 118 opening for pituitary stalk, 167 Dissecting instruments, 29, 30 Dorsum sellae, 166 front of. 115 relation to basi lar artery te r· mination, 168 side of, 114- 115 to p o f, 114- 11 5, 170, 179180 Doyen, Emile, 3 Drake, Charles, 16, 18 Drills and burrs, 24, 41 Dura of crista g'dlli . 130

exposure o f. 40, 49-50 frontal,49-50 margin of, 62 as o ptic canal margin, 128 of orbital roof p rojections. 129, 13 1 of posterior cli noid process, 99, 102, 118 of sphenoid wi ng, 65, 68, 72, 86 of sylvian fi ssure, 50 tempordl, 50 venous sinus in , 114-115 Dural flap , 4 1

E Electrocautery, 24-26, 39. 40-

41 F Facial nerve fro ntalis branches of, 40 origin o f. 17 1 "'alciform ligament, 167 Fishhook retractors. 22-23, 39,

"1aps cranial. 39-40 dural,41 scalp. 39. 47-48 Foramen ovale. 38 Forceps electrocautery, 24-26 jewelers, 27, 29. 56. 62 to open and separate arachnoid , 64-65, 67 "' rontal M-2 arteries, 61, 70, 75-76. 88-89 microaneurysllIs of. 76 frolll middle cerebral M-I artery. 75. 89 from middle cerebral M-2 artery. 6 1, 76, 80, 88, 146 aneurysm flanked by, 78-

Frontal dura. 49-50 Frontal lobe. 53, 58-59, 6 1-64, 66,69.72,74-75,77, 81-83,85-87,9 1,180. 188.192 adhesion 10 optic tracl, 104 adhesion to temporal lobe, 56,71 base o f, 131 c1evillion o f, 52, 124

Index le ft, 139- 140, 150 in quadrangular zone of chiasmatic cistern, 132-

133

righi , 139, 143, 150, 155, 171 Frontolaleral craniotomy, right,

Fronto-orbital arteries, 114 , 124 , 132-133, 137, 14 2, 14 7, 154 left, 117, 133, 140, 143-- 144. 149- 15 1, 155-159,162-

163

right, 14 3- 144 , 156. 163 fo-rontoparietal sutu re line, I , 37 Frontopolar arte ries left. 140, 149 low ta keoff o f. 155 low ta keoff o f. 125, 149, 155 rig ht, 149 common trunk with anery o f Heubner, 126, 15 1 Fron tosphenoidal suture li ne, 1,37 Fro ntotemporal bone nap, 39-

G Gigli saw, 3, 24, 40 Gyrus rectus, 65, 98, 105, 120, 123, 124. 128, 16 1, 178 initial exposu re o f, 124, 132-

13'

le ft, 114, 137, 142, 14 7-149, 155-156, 158. 162- 163 medial surface o f, 133 rig ht, 112, 11 4. 133, 136, 146- 147,151. 155- 156 ve in on, 99, 143 H

Hayes, George, 5 Head holder, 13-16 Hemorrhage, suba rach noid and adhesions in arachnoid sheath of thalamic perforalOrs, 170, 182- 183 thicke ned arach noid membra ne of Liliequ ist fro m, 170. 176 and xanthoch romic pigment from hemoglobin, 15 1 Heu bner recurrent arte ry, 57, 80-8 1,9 1. 102, 105,108, 113, 134- 135, 142- 143,

14 7, 152- 155, 158. 170171,200 adherent to aneurysm al carotid arte ry bifu rcation,

cOlllmo n trunk with right fromopolar artery. 126. 15 1 course o f, 127, 164 variations in, 125 large size of, 125, 14 6, 149 left, 133, 136- 137, 140, 144, 149, 157,159, 162- 163 perfo rato r fro m, 83 relation to anterior cerebral a rtery. 95 right, 136- 137. 139, 144, 150, 157, 163 Heuer, George, 4 , 5 History o f pte riona! a pproach, 1-7 cranial saws in, 2-3 hypophyseal nap in , 5-6 osteoplastic method o f Wagner, 1-2 skin incisio ns in , 7 tre phine and melal guide of de Martel in, 3-4 Hydrocephalus. commu nicating, 94 Hypoph y.seal a pproach of Heucr a nd Dandy. 4, 56 Hypo physeal a rtery, su perior, 79,84, 95, 99, 102. 106, 120 Hypophyseal cistern , 125. 138, 14 1, 169 Hypophyseal perforators from imernal carotid artery, 95,99, 11 5, 125, 138 arachno id sheath o f, 120 fro m posterior communicating artcry, 95, 102 Hypothala mic perforato rs from internal carotid artery. 81,95, 102- 103, 106, 11 8, 14 8, 159, 179 from posterio r commun icating artery, 95, 102-103 stuck to anterior commu nicating artery aneu rysm, 125, 149 Hypothalamus. mammillary body of, 166, 169, 17 1 Hyrtl's ca nal, 4 1

205 I Incisions in skin, 7. 39, 46 Instrumentation, 11-30 bone-removal, 24 d issccting, 29, 30 electroca u tery, 24-26, 39, 40-4 1 external, 13-22 fishhook retracto rs, 22-23, 39, 48 intraoperative, 22-30 jewelers' fo rceps, 27, 29, 56,

62 mirrors, 29 opcrating microscope, 16-22 overhead table, 22 retf3clOrs, 26-27. 28. 48. 5 152,56,58 scissors, 27, 29, 68, 74 suction and suctioll-i rrigatio n devices, 23-24, 4 1 surgeon's chair, 16 television systcms. 22 Inte rhe mispheric fiss ure (ciste rn), 123, 124. 133, 142, 147, 158, 169 arach noid covcring of, 144, 150, 153-- 155. 160 Interpedu ncu la r cistern , 69, 9l-94, 14 1, 152, 165200 anatomy of, 165- 173, 199 ap proaches to. 170. 184-185 basilar artery bifurcation in. 189

cente r of, 172, 187, 194196

fro nlOlateral ro ute 10, 98 j unCtio n with a mbient and C.t rOlid cisterns. 169. 172,190, 192 right lateral ponion of, 185-

186

Interpeduncu la r fossa o f midbrain, 17 1 Irrigating flu id , 23--24

J ewelers' forceps. 27, 29, 56, 62

K Kempe. Ludwig, 6, 39 Kcy and Retzius membra ne. Set Arachnoid membrane o f Lilieq uist

Index

206 L Lacrimal artery, 5 1 Lamina lerminalis, 85, 112-

11 3, 123. 124, 125, 133148, 150- 151 , 155- 160, 162- 163, 192, 197 anatomy 0[, 172, 199 Lamina terminalis cistern, 93, 125, 134- 136, 144 , 149, 169 anatomy of, 160-- 162 arachnoid bands at margin of, 125, 141 structures in, 126 Liliequist membrane. See Arachnoid mem brane of Liliequist

M Mammillary body of hypot halamus, 166, 169, 171 Medu lla oblongata, 17 1 Medu llary perforators from basilar artery. 115, 177 Meningo-orbital artery. 41, 5 1 Microscissors. 27.29.68, 74 Microscope, operating, 16-22 advantages of, 17- 18 disadvantages of, 17 Midbrain anatomy of, 165, 166 interpeduncular fossa of, 171 peduncle of (pyramidal tract), 169, 171- 172, 189 left. medial side of, 177 , 180- 181 Mirrors at tip o f probes, 29

Obalinski, Alfred, 3 Ocu lomotor nerves, 65, 69, 94, 98-100, 102. 104, 106110, 11 2, 11 5, 12 1, 152, 169, 176, 178- 179.182183. 185. 187, 190, 193194, 196, 199 adhesion to carotid artery aneurysm, III adhesion to uncus of temporal lobe, 170, 184 angulation of, 83 base of, 175 course of, 172 entering cavernous sinus, 170,174,192,195

le ft , 114. 180- 18 1, 188,200 origins of, 165 oSlium o f, 167, 174 relation to basilar artery bifurcatio n. 19 1 right, 114 , 166. 171, 177, 180- 18 1, 188,200 separating superior cerebellar artery. 172, 186 Oculomotor trigone, 167, 172 Olfactory bulb, 124, 131 O lfactory cistern , 123, 124, 129 Olfactory nerves, 124 Olfactory stria, medial and lateral, 124 Olfactory trace, 53, 95, 98--99. 102, 105, 124, 132-133, 155, 17 1 lower portion of, 128 left. 158-- 159 middle portion of, 129 rig ht, 156 upper portion of, 130, 13 1 Operating microscope, 16-22 Operating room table. 13 Ophthalmic artery, 95 left, 148 origin of, 104, 148 Optic canal, 38, 167 dural margin of, 128 Optic chiasm, 80-84, 9 1, 106, 112, 11 4, 11 7- 120, 123, 133, 136, 140- 144, 146152. 154-156, 158, 160, 162, 166,179,192,197, 199 lateral side of, 157 prefi xed, 124 , 125-126, 134135, 150 Optic cistern, 124 Optic nerves, 52, 66, 69, 77, 82-83, 100-101, 103105, 107- 108, 110, 112, 11 4, 11 8-- 120, 167.175, 182- 184. 186-187, 194195 arachnoid band over, 67 arachno id between, 98--99, 102, 11 6, 132- 134,148, 160 arachnoid covering of, 53. 74 lateral portion in carotid cistern, 123 left, 106, 117, 133, 138, 140143, 146- 152, 154-156, 158--160,162, 192, 199

in orbit, 124 right, 98-99, 102, 106, 11 6117.121, 128,133.138, 141 - 14 3, 146-- 150,152, 154- 160,162,171, 174, 176, 179- 181 . 192,199 unusual relation to posterior clinoid process, 170, 178 Optic tract, 79-85, 89-9 1, 106, 108- 110, 11 5, 120, 123, 135-136, 145,150- 15 1, 154, 161- 163, 169,179, 185-186, 194-195, 197198, 200 adhesion to frontal lobe, 104 right, 112, 114 , 118, 133, 138--1 44 , 146-- 149, 152, 155-159, 192, 199 terminus of, 165 view to inte rnal carotid artery, 103 Orbit dura covering roof projections, 129, 13 1 in surgical position, 42-45 Orbital fissure, superior. 38 O rbital gyrus, medial. 123, 124

p Parietosphenoidal suture line, 1,37 Parictotemporal suture line, I, 37 Peduncles cerebellar, middle, 17 1 cerebral, 166 interpedu ncular cistern. Set Interpeduncular cistern midbrain. 169, 171-172, 189 Perforated substance, anterior,

front border of, 124 perforators to, 57, 79, 84, 89, 118 Perforating arteries on aneurysm dome, 78 from anterior cerebral A- I artery, 57. 79-80, 82, 84, 92,106, 14 1- 142, 16 1163,170,184,186, 199 from anterior choroidal artery, 183 from anterior communicating artery, 11 2, 157 to anterior perforated substance, 57, 79, 84, 89, 11 8

207

Index arachnoid fibers from, 57, 90 from artery of Heubner, 83 hypo physeal. Su Hypophyseal perforators hypothalamic. Su Hypothalamic perforatOrs from internal carotid artery. Su Carotid artery. internal, perforators from medu llary, from basilar artery, 115, 177 from middle cerebral M- I artery, 57, 79-81, 89-92, 125 , 146-147,170,181, 184-187, 190-191, 200 from posterior cerebral arter-

P_I, 165, 168, 188, 195 P-2, 186, 190-19 1 from posterior com municating artery. Su Communicating artery, posterior, perforators from stria thalam ic, 57, 89-92 thalamic. See Thalamic per· foralO rs Pericallosal cistern, 123 Periosteal patch elevated from frontal bone, 39, 47 Petrous pyram id , 42-45 PhoLOgraphy, 33-35 current techniques in, 34-35 Pituitary gland, 97, 118, 140,

171 in fu ndibulum of. 166 Pituitary stalk , 82, 95-96, 102. 104, 106, 11 0, 114 , 119, 12 1,125, 138, 140- 14 1, 146,149 opening for, in diaphragm sellae, 167 portal veins of, 11 8 surrounded by arach noid, 125, 138, 147-148, 169 Pons rostral paft of, 115, 170, 172, 174-175,179-1 8 1,186187, 190-192, 194- 196 trigeminal nerve arising from, 171 Positioning of patient, 39 importance of, II , 16 Prepontine cistern, 193, 194 Psychopathic point, 6, 39 Pterion, defin ition of, 1,37 Pterygoid plates, 38

Quadrangular zone in chias· matic ciste rn , 124. 133163 Quadrigeminal cistern , 169 Quadrigeminal plate, 166

R Raney dips, 47 Recurrent artery o f Heubner. Set Heubner recurrent artery Reil island, 7 1 Retractors, 26-27, 28, 48, 5 152, 56, 58 fishhook, 22-23, 39, 48 self· retaining. 26-27 Rongeurs, 24, 40 Rosenthal vein , basilar, 165, 174

S Saws, cranial, development of, 2-3, 24, 40 Scalp nap, 39. 47-48 Scissors, types of, 27, 29, 68, 74 Sella turcica, 37-38 Skin incisions, 7, 39, 46 Skull fixation, three·poim, 1316,39 Sphenoid wings, 37, 38, 42-43,

45 dura over, 65, 68, 72. 86 prior to removal, 49-50 removal of, 39, 40-41 Sphenoidotemporal suture line, 1,37 Sphenoparietal sinus, bridging veins to temporal lobe, 41,56,66.74 electrocoagulation of. 56, 68 Stria thalamic perforators, 57. 89-92 Subarachnoid hemorrhage and adhesions in arach noid sheath of thalamic perforalOrs, 170, 182-183 thickened arachnoid memo brane of Liliequist from , 170, 176 and xanthochromic pigment from hemoglobin. 151 Suction and suction.irrigation devices, 23-24, 4 I Sutu re lines of skull, 1,37

Sylvian aqueduct, 166 Sylvian fissure (cistern), 52, 5592.93-94, 123 anatomy of. 56-57 arachnoid over, 146 dura over, 50 lateral, 169 medial, 169 surgical opening of, 56-91 union with chiasmatic and ambient ciSlern, 169 veins in, 63, 66, 75-76, 78 branches of, 59 Sympathetic fibers on internal carotid artery, 96, 116

T Table operating room, 13 overhead , 22 Television systems, 22 Temporal arteries anterior, 70, 75, 77-79, 83, 88-89,9 1, 100, 134, 147, 184,19 1 duplicated. 190 from middle cerebral arteries, 70 M·I, 75, 89 M-2. 6 1,76,80,88, 146 aneurysm nanked by, 78,

posterior, 76 superficial . 40 Temporal lobe, 53, 56, 58-59, 6 1-62,65-66.69-70,74, 85-87,9 1,186 ad hesions with carotid artery, 100 with frontal lobe, 56, 71 aneurysm dome in , 75 bridgi ng veins to sphenopa. rictal si nus, 41,56.66,74 electrocoagulation of. 56,

dura of, 49-50 elevation of, 52 left, medial side of, 11 7, 119, 171 medial , 169 right, 120 uncus of, 69, 102, 108-109, 11 2- 113, 115, 121, 152, 174-1 75, 178, 180-183, 185, 192-193, 197-198, 200

208

Index

Tcmporal lobe (conI.) adherence to oculomotor nerve, 170, 184 left, medial side of, 117 relation to anterior choroidal artery, 95, 105 retractio n of, 83 vein on, 128 Temporalis muscle. incision of,

39,47 T entorium cerebcUi, 166 anterior reflection of, 99, 162 attach ments to clinoid processes, 165 carotid artery aneurysm adhesion to, 101 edge or margin of, 68, 105, 107-108, 11 0, 114 , 116, 121 , 134,174, 176, 184-

187,189.194,196--197 incisura of, 166 medial reflections of, 167 Thalamic perforators alllerior from internal carotid artery, 95, \02- \03, 172,

179 in arachnoid sheath, 120 from posterio r communicating artery. 82-83, 95, 102-103, 109-110,170, 172,174,176,180, 184, 187, 190. 192, 197- 198 adhesions in arachnoid sheath of, 170, 182-

183 in arach noid sheath . 198

posterior, from posterio r cerebral arteries P_I. 165, 168, 18 1. 188. 195 P-2. 186, 190- 191

Third ventricle, 145 cerebrospinal fluid in, 169 relation to basilar artery, 168 Toison , J ean, 2-3 Tremor. reduction of, 29 Trephines, d evelopment of, 34 Trigeminal ne rve. right, a rising from pons, 171 Trochlear nerve, 165, 166 ostium of, 167 Tuberculum sellae, 37-38, 4344,117,135, 148, ISS,

159

U Uncus of temporal lobe, 69, 102, 108--109, 11 2- 113, 115, 121,152,174-175, 178, 180- 183,185,192193, 197-198,200 adherence 10 oculomotor nerve, 170, 184 left, medial side o f, 117 relation to anterior choroidal artery, 95, 105 retraction of, 83

Veins in ambient cistern , 174- 175,

in interpeduncular cistern , 190- 191,200 in lamina te rminalis cistern , 127, 161 portal, of pituitary stal k, 11 8 in sulcus belween frontal lobe and olfactory cistern ,

129

in sylvian fissure, 59, 63, 66, 75-76, 78 o n temporal lobe, 128 Venous d rainage, preservation of,41 Venous sinus, dural, 114- 115 Ventricle, third, 145 cerebrospinal fluid in , 169 relation 10 basilar artery, 168 Vertebral arteries, 17 1 Von Bergma nn , Ernst, 2

W Wagner. Wilhelm, 1-2,3 Willis circle posterior, 18 1 relation 10 posterior clinoid process, 167 X Xanthochromic pigment from hemoglobin of subarachnoid hemorrhage, 151

178

basilar, of Rosenthal, 165,

174

in carotid ciste rn, 110 in cavernous si nus, unusual, 97,1 18--119 in chiasmatic ciste rn , 163 on gyrus rectus, 99, 143

y Yasargil, Gazi, 6-7, 16

Zygoma. frOll tal process of, 44