Atlas of veterinary diagnostic imaging by Grupo Asís

Presentation brochure Fernando Liste Burillo

Las técnicas de diagnóstico por imagen a las que tienen acceso los veterinarios ofrecen diferentes ventajas respecto a la región o estructura orgánica que quiera evaluarse. El beneficio que puede obtenerse de ellas parte del conocimiento que el veterinario tenga de la técnica, su manejo y de la interpretación de los resultados. Por eso, en este atlas se han querido agrupar radiología, ecografía, tomografía computerizada y resonancia magnética, y, a través de más de 500 imágenes, mostrar su utilidad y aplicación según el área anatómica a examen. En los 6 capítulos del libro: descripción de las técnicas de diagnóstico por imagen, diagnóstico por imagen del tórax, abdomen, cabeza, columna vertebral y extremidades, se describen las aplicaciones de cada una de las técnicas esbozando sus indicaciones y contraindicaciones y se muestran imágenes características de la anatomía normal y de los distintos patrones de enfermedad en cada una de las áreas.

Fernando Liste Burillo

Un libro fundamental destinado a profesionales y estudiantes de la materia que invita a aprovechar todo el potencial diagnóstico que poseen las actuales técniServet (División de Grupo Asís Biomedia S.L.) cas de imagen en medicina veterinaria.

ATLAS OF VETERINARY DIAGNOSTIC IMAGING

Centro Empresarial El Trovador, planta 8, oficina I Plaza Antonio Beltrán Martínez, 1 • 50002 Zaragoza (España) Tel.: +34 976 461 480 • Fax: +34 976 423 000 • www.grupoasis.com

ATLAS OF VETERINARY DIAGNOSTIC IMAGING

The publishing strength of Grupo AsĂs Editorial Servet, a division of Grupo AsĂs, has become one of the reference publishing companies in the veterinary sector worldwide. More than 15 years of experience in the publishing of contents about veterinary medicine guarantees the quality of its work. With a wide national and international distribution, the books in its catalogue are present in many different countries and have been translated into nine languages to date: English, French, Portuguese, German, Italian, Turkish, Japanese, Russian and Chinese. Its identifying characteristic is a large multidisciplinary team formed by doctors and graduates in Veterinary Medicine and Fine Arts, and specialised designers with a great knowledge of the sector in which they work. Every book is subject to thorough technical and linguistic reviews and analyses, which allow the creation of works with a unique design and excellent contents. Servet works with the most renowned national and international authors to include the topics most demanded by veterinary surgeons in its catalogue. In addition to its own works, Servet also prepares books for companies and the main multinational companies in the sector are among its clients.

diagnostic imaging

Fernando Liste Burillo

Atlas of veterinary

ATLAS OF VETERINARY DIAGNOSTIC IMAGING Fernando Liste Burillo

Un libro fundamental destinado a profesionales y estudiantes de la materia que invita a aprovechar todo el potencial diagnóstico que poseen las actuales técnicas de imagen en medicina veterinaria.

ATLAS OF VETERINARY DIAGNOSTIC IMAGING

AuthorS: Fernando Liste Burillo (coord.), Isidro

Mateo Pampliega, Sergio P. Monteagudo Franco, Alberto Muñoz González.

Format: 22 x 28 cm. Number of pages: 304. Number of images: 750. Binding: hardcover.

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Diagnostic imaging techniques offer various advantages related to the organic structure or region to be evaluated. Thus, in this atlas, the radiology, ultrasound, computed tomography, and magnetic resonance imaging sections have been grouped together according to the anatomical area being examined and, through over 700 images, the utility and relevance of each technique is demonstrated. The 6 chapters of this book describe diagnostic imaging techniques for the thorax, abdomen, head, spinal column and limbs, showing the applications, indications and contraindications of each technique and using characteristic images of anatomically normal areas and the different patterns of illness affecting each of these areas.

Presentation of the book Common sense dictates that the foreword of a scientific and technical book is usually written by an expert in the relevant area. The reader is warned that it is not the case here. I met Fernando back in the summer of 1997 when he reached the final phase of the interview process as we sought to select a candidate for the professorship of Anatomy and Embryology for the newly created Veterinary Medicine degree at the Centro Universitario San Pablo-CEU (now Universidad CEU-Cardenal Herrera). I was a member of the interview panel. We had already decided that the person we sought would be the first member, and subsequently the director, of the future Department of Animal Medicine and Surgery. The decision was not difficult, as Fernando had the right clinical profile. He had come from Tufts University Veterinary College (Massachusetts, USA), where he had specialising in diagnostic imaging, a discipline he wished to pursue further. It was an intense few years, during which Fernando was gradually orienting his teaching towards disciplines such as clinical anatomy and radiology, while simultaneously setting up the Diagnostic Imaging Service at the Veterinary Hospital. I became familiar with his approach to work, which was methodical, orderly, meticulous, demanding, and characterised by a desire to excel. Thanks to his tenacity in continuously seeking improvements to facilities and equipment, the Diagnostic Imaging Service was expanded to include radiology, ultrasound, endoscopy and computed tomography. This atlas is the work of a clinical academic, someone who is passionate about teaching the discipline he loves. This dual profile, professor and veterinary surgeon, ensures that this Atlas of Veterinary Diagnostic Imaging is designed as a systematically organised and illustrated learning and consultation tool. Knowing its author, it couldnÂ´t have turned out any other way. Blas Enrique Ferrer Professor of Animal Nutrition, Department of Animal Science, Universidad PolitĂŠcnica, Valencia, Spain.

Atlas of veterinary diagnostic imaging

The authors Fernando Liste Burillo (Coordinator) Doctor of Veterinary Medicine, University of Zaragoza, Spain. Professor of Radiology, Department of Veterinary Medicine and Animal Surgery and Head of Veterinary Diagnostic Imaging at the Clinical Veterinary Hospital, Universidad CEU-Cardenal Herrera, Valencia, Spain.

Isidro Mateo Pampliega Head of Neurology and Neurosurgery at the Clinical Veterinary Hospital, Universidad Alfonso X el Sabio, Madrid, Spain.

Sergio P. Monteagudo Franco Head of Diagnostic Imaging, Clinical Veterinary Hospital, Universidad Alfonso X el Sabio, Madrid, Spain.

Alberto Muñoz González (Collaborator) Professor of Radiology and Physical Medicine at the Faculty of Medicine, Universidad Complutense, Madrid.

hkeita/shutterstock.com

Director of Resonancia Magnética Veterinaria, Sierra de Madrid Veterinary Hospital, San Agustín del Guadalix, Madrid, Spain.

Communication services Web site Online visualisation of the sample chapter. Presentation brochure in PDF format. AuthorÂ´s CV. Sample chapter compatible with iPad.

www.grupoasis.com/promo/diagnostic_imaging

ATLAS OF VETERINARY DIAGNOSTIC IMAGING Fernando Liste Burillo

Table of contents 1. Diagnostic imaging techniques Radiography Radiographic tables suggested for different anatomical regions

Bronchial pattern Vascular pattern

Non-cardiac thoracic ultrasound Computed tomography of the lung Abnormalities of the pleural space

Computed tomography (CT)

Mediastinal disorders

Ultrasound

Oesophageal disorders

Magnetic resonance imaging (MRI)

Abnormalities of the diaphragm

Basic principles of MRI Weighting and enhancement of the image: T1 and T2-weighted sequences Inversion-recovery sequences Image formation Special considerations

Selecting the appropriate diagnostic imaging method References

2. Diagnostic imaging of the thorax

References

3. Diagnostic imaging of the abdomen Radiographic anatomy of the abdomen: diagnostic approach Abdominal contrast radiography

Tomographic anatomy of the abdomen Liver Hepatomegaly Decreased liver size

Radiographic anatomy and diagnostic approach

Spleen

Radiographic anatomy of the heart

Pancreas

Heart-size evaluation

Lung field and pleural space Mediastinum Diaphragm Thoracic skeletal structures and cranial abdomen Tomographic anatomy of the chest Cardiomegaly Pulmonary patterns Interstitial pattern Alveolar pattern

Splenomegaly

Gastrointestinal tract Stomach Contrast studies

Small intestine Large intestine

Urogenital system Upper urinary tract: kidneys and ureters Lower urinary tract: bladder, urethra and prostate Genital tract Uterus and ovaries Testicles

Adrenal glands

Intra-axial lesions

Lymph nodes

Cerebrovascular disease

Interventional abdominal ultrasound

Haemorrhagic lesions

References

4. Diagnostic imaging of the head Radiographic anatomy, computed tomography and magnetic resonance imaging of the head Techniques used to scan the brain Conventional radiography Ultrasound

Ischaemic injury (stroke) Inflammatory diseases Of infectious origin Non-infectious Degenerative diseases Congenital anomalies Metabolic/nutritional encephalopathies Neoplasms Gliomas Pituitary neoplasms Metastatic lesions

Changes associated with intracranial lesions

Computed tomography

Hydrocephalus

Magnetic resonance imaging

Oedema

Other techniques

Brain herniation

Neuroanatomical considerations

Techniques used to examine the skull, sinuses and ear Radiography Ultrasound Computed tomography Magnetic resonance imaging

Brain: intracranial lesions Parameters to consider Anatomical origin of the lesion

Examination of the skull, sinuses, ear and eye: representative pathology Cranial vault and skull base Inflammatory disorders: osteomyelitis Trauma Congenital anomalies Hydrocephalus Occipital dysplasia Neoplasms

Nasal cavity and sinuses

Presence of single or multiple lesions

Inflammatory disorders

Site

Neoplasms

Shape Margins Growth pattern Signal intensity and signal density Contrast capture and enhancement

Extra-axial lesions Lesions of the skull

Mandible and temporomandibular joint Trauma Mandibular fractures Temporomandibular dislocation Degenerative processes Craniomandibular osteopathy

Ear

Lesions of the meninges

Nasopharyngeal polyps

Lesions of the peripheral nerves

Otitis media/interna

Lesions of the choroid plexus

Neoplasms

Eye and periorbital region Intraocular lesions Cornea and anterior chamber Crystalline lens Vitreous body and retina Lesions of varied location

Retrobulbar lesions Optic nerve and extraocular muscles

Soft tissues of the neck: pharynx, larynx and hyoid References

5. Diagnostic imaging of the spine Radiographic anatomy, computed tomography and magnetic resonance imaging of the spine Examination of the spine: indications for different diagnostic imaging techniques Conventional radiography and myelography Ultrasound Computed tomography (CT) Magnetic resonance imaging (MRI)

Imaging diagnosis of spinal disease Extradural lesions Intradural-extramedullary lesions Intramedullary lesions Nerve root diseases

References

6. Diagnostic imaging of limbs General concepts The forelimb Shoulder Elbow Carpus and hand

The hindlimb and hip Hip Stifle Tarsal region and foot

Bone growth disorders Osteochondrosis/osteochondritis Imaging findings in osteochondrosis

Elbow dysplasia Imaging findings in elbow dysplasia

Hip dysplasia Radiographic features

Aseptic necrosis of the femoral head (Legg-CalvĂŠ-Perthes disease) Radiographic features

Panosteitis Radiographic features

Hypertrophic osteodystrophy Radiographic features

Retention of growth cartilage Radiographic features

Premature epiphyseal closure Radiographic features

Degenerative joint disease Imaging findings in osteoarthritis

Fractures and dislocations Types of fractures Evolution of fracture callus Dislocations Poor union/nonunion of fractures

Aggressive and non-aggressive bone lesions Characterisation of bone lesions Site Lysis pattern Periosteal reaction Continuous periosteal reactions Interrupted periosteal reactions Zone of transition between lesion and healthy bone Cortical alterations Variation in the radiographic image over a short period of time

Distinguishing bone tumours from osteomyelitis

References

DIAGNÓSTICO POR IMAGEN DEL TÓRAX

DIAGNOSTIC IMAGING

OF THE SPINE Isidro Mateo Pampliega Alberto Muñoz González (collaborator)

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Radiographic anatomy, computed tomography and magnetic resonance imaging of the spine Figures 1-8 show the main anatomical details of the spine with different imaging techniques: conventional radiography, computed tomography and magnetic resonance imaging.

14 1

9 10 15

13 11

6 7 8

Figure 1. Lateral radiograph of a dog’s cervical spine after injecting iodinated contrast material (iohexol) into the subarachnoid space at the cisterna magna, to outline the contour of the spinal cord.

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Figure 2. Ventrodorsal radiograph of a dog’s cervical spine after injecting iodinated contrast material (iohexol) into the subarachnoid space at the cisterna magna, to visualise the outline of the spinal cord.

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9 24

11 12

26 27 25 22

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Figure 3. Lateral radiograph of a dog’s thoracic spine after injecting iodinated contrast material (iohexol) into the subarachnoid space at the cisterna magna, to visualise the outline of the spinal cord.

RADIOLOGY

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28 29

24 25 26

Figure 5. Lateral radiograph of a dogâ&#x20AC;&#x2122;s lumbar spine after injecting iodinated contrast material (iohexol) into the subarachnoid space at the dorsal L5-L6 intervertebral space, to visualise the outline of the spinal cord.

Figure 4. Ventrodorsal radiograph of a dogâ&#x20AC;&#x2122;s thoracic spine after injecting iodinated contrast material (iohexol) into the subarachnoid space at the cisterna magna, to visualise the outline of the spinal cord.

1. Atlas. 2. Spinous process of the axis. 3. Dens (odontoid process). 4. Spinous process. 5. Tympanic bulla. 6. Angular process of the mandible. 7. Transverse process. 8. Transverse processes of C6. 9. Articular facet of the cranial vertebral. 10. Articular facet of the caudal vertebra. 11. Dorsal contrast column.

12. Ventral contrast column. 13. Cisterna magna. 14. Cisterna magna. 15. Basilar artery. 16. Cervical intumescence. 17. First rib. 18. Arch of the atlas. 19. Transverse foramen. 20. Ventral crest of the axis. 21. Accessory process. 22. Costovertebral junction.

23. Spinous process of T1. 24. Intervertebral foramen. 25. Intervertebral disc. 26. Vertebral body. 27. Anticlinal vertebra. 28. Lumbar intumescence. 29. Cauda equina. 30. Sacrum. 31. Promontory. 32. Sacral wing. 33. Sacral foramina.

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b 2 1

22 3 19

10 22 28

Figure 7. Tranverse CT images of different spinal segments after the injection of contrast medium. The anatomical sections are C1 (a), C6 (b), T10 (c) and L4 (D). 29

29 32

Figure 6. Ventrodorsal radiograph of a dogâ&#x20AC;&#x2122;s lumbar spine after injecting iodinated contrast material (iohexol) into the subarachnoid space at the dorsal L5-L6 intervertebral space, to visualise the outline of the spinal cord.

Figure 8. Tranverse MRI images of different spinal segments obtained at C4-C5 (a), T2-T3 (b), T13-L1 (c), L4-L5 (d) and L7-S1 (e).

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TOMOGRAPHY

MAGNETIC RESONANCE

Exploration of the spine: Indications for different diagnostic imaging techniques Conventional radiography and myelography Radiography is a useful diagnostic technique to first approach the diagnosis of spinal injuries, especially with diseases causing bone disorders. In order to adequately assess the spine, the main X-ray beam should penetrate perpendicular to the area under study. In some cases, sedation or general anaesthesia are required to ensure correct positioning. Setting up an adequate radiographic technique (mAs, Kvp) as well as proper collimation, filtering and focus-film distance will determine image quality. Modern digital equipment automatically optimises some of these parameters, which results in improved radiographic quality compared with old conventional imaging. Myelography is a special radiographic technique that involves the injection of radiopaque contrast medium into the subarachnoid space, thereby enabling visualisation of the outline of the spinal cord. Contrast media must be iodinated, non-ionic and with low osmolarity. Highosmolarity contrast media are extremely irritating to the central nervous system. Iohexol (240300mg/ml) or iopamidol (200mg/ml), with osmolarities between 600 and 700 mOsm, are commonly used. The contrast medium must be injected into the subarachnoid space through the cisterna magna in the case of cervical myelography, or into the lumbar subarachnoid space at the dorsal intervertebral foramen of L4-L5 or L5-L6 in the case of lumbar myelography. Some authors believe that the injection of contrast medium must always be performed into the lumbar subarachnoid space in order to observe its cranial progression. However, it is generally recommended to perform the contrast medium injection closer to the area of the suspected lesion. Doses of 0.3 and 0.4 ml/kg of contrast medium are used for cervical and lumbar myelography respectively. After injecting the contrast agent in the cervical region, the patient should be positioned with its head elevated to facilitate gravitational flow to the caudal segments. Some of the complications derived from myelography are the following: ■■ Injection of contrast medium outside the subarachnoid space (epidural, subpial). ■■ Cord damage (with much more severe effects in case of cervical punctures). ■■ Exacerbation of neurological signs after contrast medium injection. ■■ Seizures after anaesthesia. ■■ Intracranial subarachnoid haemorrhage.

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MRI MRI provides better soft-tissue contrast than any other imaging technique, which makes it the most suitable method for the study of diseases affecting the spinal cord, nerve roots, meninges and intervertebral discs. The study protocol will depend on the type of magnet, the field strength and the size of the animal. The patient should be placed in dorsal recumbency as close as possible to the antenna. Initially, it is advisable to use a sagittal T2-weighted sequence of the spine and then plan further cross-sectional imaging on the areas of interest. Transverse images should be also T2-weighted with 3-4 mm of thickness depending on the patientâ&#x20AC;&#x2122;s size. This type of study is generally sufficient for the diagnosis of degenerative disc disease and herniation (strong hypointense signal). However, additional T1-weighted or fat-saturation sequences before and after injecting a paramagnetic contrast agent may be required in cases of a suspected infectious or neoplastic disease. Typical anatomical landmarks to identify the location of thoracolumbar lesions are the last thoracic vertebra (last rib), the position of the celiac trunk and the cranial mesenteric artery (between T13-L2) and the lumbosacral joint (Fig. 12).

Figure 12. Vascular landmarks for vertebral localisation on MRI images. Lateral T2-weighted sagittal image of the lumbar spine showing the celiac trunk and cranial mesenteric artery ventral to the L1-L2 disc space (arrows). The arrow indicates a disc protrusion at L7-S1.

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Imaging diagnosis of spinal disease Extradural lesions This section includes conditions that originate in the extradural space or surrounding bone/ ligamentous structures and compress the cord or nerve roots.

Extradural haemorrhage Extradural haematomas can be found as a result of spontaneous bleeding or trauma. MRI or CT imaging features of the haemorrhage will depend on its stage (Fig. 13).

Figure 13. Epidural haemorrhage. Transverse CT image at the body of L3 showing right dorsal displacement of the cord due to an epidural mass located on the left ventral and lateral aspect of the vertebral canal (arrow).

Inflammatory diseases Inflammatory diseases of infectious origin primarily affect young animals. The presentation is usually subacute or chronic. Patients initially present with non-specific pain or resistance to manipulation, and develop neurological symptoms later on.

Vertebral osteomyelitis. Diskospondylitis In both cases, the most common cause is a bacterial or fungal infection. Microorganisms can reach the bone or the intervertebral disc from a foreign body such as a spike, or from haematogenous spread due to concomitant urological respiratory or dermatological infections.

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Figure 14. Radiographic and CT features of diskospondylitis. A: Lateral radiograph of the lumbosacral spine (a) showing rough contours of the cranial and caudal endplates at L7-S1 (arrows). B: Transverse CT image at T12-T13 showing severe destruction of the intervertebral disc.

Vertebral osteomyelitis is also known as spondylitis and can extend from the body to the lamina and pedicles. Radiographic features usually include focal bone lysis and sclerosis at the ventral aspect of the vertebral body and soft-tissue swelling. In diskospondylitis, the infection reaches the intervertebral disc after direct contact or haematogenous spread. The structure of the intervertebral disc is severely affected and lysis of the adjacent vertebral endplates is often observed, with additional roughening of the articular surfaces in the joint (Fig. 14). The most usual location for diskospondylitis is the lumbosacral space. Although the lesion can be solitary, it is not uncommon to find multiple affected intervertebral discs. Thus, a comprehensive radiographic study of the spine is highly recommended in these cases. The radiographic changes associated with diskospondylitis are not directly related to the clinical signs; a treated animal with clinical improvement may show worsening of lesions on radiographs for several days. In general, bone lysis and sclerosis on radiographs and CT scans are considered signs of progression and remission of the disease respectively. On an MRI image, a progressively decreased volume of the soft-tissue mass around the joint is a positive sign for remission. The radiographic features of diskospondyltis have already been discussed. However, these signs may not be apparent until 2 weeks after the onset of the disease. Myelography is useful to detect focal cord compression from a soft tissue mass effect in diskospondylitis. Intensity changes at the endplates (hypointense on T1 -weighted sequences and hyperintense T2-weighted) along with heterogeneous enhancement and presence of a soft tissue mass around the space are MRI features of diskospondyltis (Fig. 15).

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TOMOGRAPHY

Figure 15. Transverse MRI sections of the lumbar spine showing diskospondylitis at L1-L2. T1-weighted images before (a) and after (b) paramagnetic contrast medium injection and with fat suppression (c). Note the marked, heterogeneous contrast uptake at the intervertebral disc (arrows), as well as the formation of a soft tissue mass on the ventral aspect of the vertebral canal (arrows).

Epidural and paraspinal abscesses Spinal and paraspinal abscesses are rare, and usually occur due to the extension of infectious diseases in adjacent areas. The most obvious radiographic changes are observed on MRI, which typically show a mass with prolonged relaxation times (hypointense on T1-weighted sequences and hyperintense on T2-weighted sequences) with increased contrast uptake (Figs. 16 and 17).

Figure 16. Epidural abscess. Transverse T2-weighted (a) and T1-weighted (b, c) MRI images before (a, b) and after (c) the injection of paramagnetic contrast medium at the level of L1 in the same animal as in Figures 14 and 15. The soft tissue mass displaces the cord to the right and shows a hyperintense signal on the T2-weighted image, with additional ring-like contrast uptake (arrows).

Figure 17. Paraspinal abscess. Transverse T2-weighted MRI images at the level of L5-L6 (a), body of L5 (b) and L4-L5. There are two ovoid structures showing signal voidÂ (*) within the epaxial muscles and the left retroperitoneal cavity (arrows) respectively. Both abscesses are connected by means of a newly formed duct (arrows).

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Injuries Spinal trauma originates injuries on the cord or surrounding bone structures (Figs. 18 and 19). An initial radiographic study of the whole lateral spine should be performed. Dorsoventral, ventrodorsal or oblique views can also be informative. However, it is important to remember that the patient should be handled carefully in this case as improper handling could aggravate the clinical picture. Non-contrast, conventional radiography might lack sensitivity for the detection of minor fractures or subluxations. Myelography allows assessment of the spinal cord in a relatively simple manner after a traumatic episode, for example to diagnose meningeal lacerations or cord compressive disease. However, it requires contrast injection and increased handling of the patient, which might not be ideal in traumatic injuries since it might affect the animalâ&#x20AC;&#x2122;s neurological status. Myelography is also somewhat insensitive for the evaluation of intramedullary lesions. Special imaging techniques such as CT or MRI can overcome these diagnostic limitations by providing cross-sectional images.

Figures 18a and 18b. Compression fracture of L3: conventional radiograph. The lateral view (a) shows a transverse comminuted fracture of L3 resulting in shortening of the vertebra and misalignment of the vertebra with the caudal vertebrae. The ventrodorsal view (b) shows multiple comminuted fragments around the fracture site as well as shortening of L3. Additional fractures of the right transverse processes of L2 and L3 are noted (arrows).

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TOMOGRAPHY

Figures 19a and 19b. Vertebral subluxation: conventional radiography. (a) Lateral view showing a slight malalignment of the vertebral canal at L4-L5 with additional fracture of the articular facets (arrow) and a small chip fragment ventral to the cranial aspect of L4. (b) Ventrodorsal view showing right lateral displacement of L4 with respect to L5 and vesical distension (arrows).

Due to its high sensitivity to detect bone lesions, CT is the technique of choice for the initial evaluation of trauma patients. Cross-sectional imaging can easily detect small bony fragments inside the vertebral canal, acute bleeding or abnormalities on the articular processes of the lamina. Diagnostic limitations of spinal CT include inability to detect ischaemic lesions within the cord parenchyma or small volumes of non-calcified disc material extruded dorsally into the vertebral canal (Fig. 20).

Figure 20. CT image of a lumbar vertebral fracture in a dog. (a) Multiplanar sagittal reconstruction showing a bony fragment in the vertebral canal (arrow). (b) Detail of a dorsal 3D reconstruction of the lumbar spine showing fracture of the articular processes (arrows). (c) 3D transverse view reconstructed image showing bony material at the ventral aspect of the vertebral canal (white arrow) and fracture of the spinous process (red arrow).

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MRI is able to recognise an ischaemic lesion within the spinal cord as it appears hyperintense on T2-weighted images. However, MRI is less sensitive than CT when it comes to detecting bone lesions (Fig. 21). T1-weighted images with fat saturation after intrathecal injection of gadolinium will help in the recognition of post-traumatic fistulae or brachial plexus damage.

Figure 21. MRI findings in spinal trauma. Transverse image at the level of the T10-T11 disc space showing a fracture of the vertebral pedicles (arrows) and presence of disc material dorsal and lateral to the cord (arrow), which shows a hyperintense signal and is partially compressed.

Congenital anomalies There is a variety of congenital spinal defects in dogs and cats that are clinically silent and diagnosed as incidental findings when radiographic studies are performed for other reasons. Therefore, these vertebral malformations should not be immediately linked to the clinical picture in patients with neurological signs.

Atlantoaxial subluxation This particular condition has a higher incidence in toy breeds and is caused by a malformation of the odontoid process of the axis, which may be absent (agenesis), hypoplastic or incompletely fused to the vertebral body of C2. This malformation causes atlantoaxial instability, with an increased distance between C1 and C2, which should be no more than 2-3 mm in normal dogs (Fig. 22). The radiographic diagnosis of atlantoaxial subluxation requires a lateral view to confirm the dorsal displacement of the spinous process of the axis from the dorsal arch of the atlas and a ventrodorsal or slightly oblique view to visualise the dens. Individuals with atlantoaxial subluxation often present with additional malformations such occipital dysplasia, hydrocephalus or syringomyelia. Thus, CT or MRI imaging of the brain and spine is highly recommended before planning any surgical correction of this disorder.

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Presentation brochure Fernando Liste Burillo

Fernando Liste Burillo

ATLAS OF VETERINARY DIAGNOSTIC IMAGING

Centro Empresarial El Trovador, planta 8, oficina I Plaza Antonio Beltrán Martínez, 1 • 50002 Zaragoza (España) Tel.: +34 976 461 480 • Fax: +34 976 423 000 • www.grupoasis.com

ATLAS OF VETERINARY DIAGNOSTIC IMAGING