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ECBSE Ultrasound of the Neck Gaitini ‌.

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EFSUMB Course Book Student Edition Editors: Jan Tuma, Radu Badea, Christoph F. Dietrich

Ultrasound of the Neck Diana Gaitini 1, Evans RM 2, Ivanac G 3 1

Ultrasound Unit, Department of Medical Imaging, Ramban Health Care Campus and Faculty of Medicine Technion, Israel Institute of Technology, Israel 2 Department of Diagnostics, Abertawe Bro Morgannwg Univesity Health Board, Wales, UK 3 Department of Diagnostic and Interventional Radiology, Dubrava University Hospital and Medical School, University of Zagreb, Zagreb, Croatia

Corresponding author: Ass. Clin. Prof. Dr. Diana Gaitini Department of Medical Imaging Rambam Health Care Campus and Faculty of Medicine Ha'alya Ha'shnia 8, 31096 Haifa, Israel.

Phone: 972-4-8543675; 972-50-2061271 Fax: 972-4-8543303 Email: d_gaitini@rambam.health.gov.il Acknowledgment: None.

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Content Introduction ................................................................................................................. 2 Thyroid gland………………………………………………………………………………... 2 Examination Technique .......................................................................................... 2 Anatomy .................................................................................................................. 4 Congenital Anomalies ............................................................................................. 6 Focal Disease ......................................................................................................... 8 Diffuse Disease ..................................................................................................... 15 Parathyroid gland………………………………………………………………………… ..18 Anatomy ................................................................................................................ 18 Hyperparathyroidism ............................................................................................. 19 Lymph nodes………………………………………………………… …………………….23 Anatomy .............................................................................................................. . 23 Lymphadenopathy ............................................................................................... .25 Salivary Glands…………………………………………………………………… …….. ..27 Anatomy ................................................................................................................ 27 Enlarged Salivary Glands...................................................................................... 28 Neck Vessels……………………………………………………………………………… .29 Carotid Arteries ..................................................................................................... 29 Vertebral Arteries .................................................................................................. 36 Jugular Veins ....................................................................................................... 37 Recommended reading…………………………………………………………………… 39

Introduction Ultrasound is (US) the first used imaging modality for the examination of the neck.

The superiority of ultrasound examination in comparison with palpation in the detection of lymphadenopathy, salivary glands and other soft tissue pathologies has been proved. US are the most sensitive imaging test for the examination of thyroid gland focal lesions and diffuse abnormalities in the thyroid parenchyma. Colour and spectral Doppler capabilities allow for characterization of mass vascularization and for the accurate evaluation of neck vessels. Carotid sonography is increasingly becoming the first and often the sole imaging study for the investigation of carotid stenosis. Non-invasive, accurate, and cost-effective, US provide morphologic and functional information. US have an important role in the guidance of interventional procedures, for diagnostic purposes-such as fine-needle aspiration (FNA) and coreneedle biopsy (CNB) - and for percutaneous treatment.

Thyroid Gland Examination Technique

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The neck is examined while the patient is lying supine and the neck hyperextended, sometimes with the aid of a pillow placed below the shoulders [Figure 1], with a high frequency linear transducer (usually 5-12 MHz), allowing a penetration of about 5 cm and a resolution of 0.7-1 mm, never achieved by any other imaging method [Figure 2]. Thyroid scans are performed at several levels in transverse and longitudinal planes. The whole gland and the surrounding structures may be shown in a transverse extended-field-of-view scan of the neck, followed by transverse and longitudinal scans through each lobe.

Figure 1 Patient position for the ultrasound examination of the thyroid. (a) The patient is lying supine and the neck hyperextended, with the aid of a pillow placed below the shoulders. (b) The operator performing the

examination.

(a)

(b)

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Figure 2 Transducer selection. A linear transducer with a high resolution frequency (5-12 MHz) provides excellent ultrasound images of the neck and in particular of the thyroid gland.

Anatomy The thyroid gland is divided into two lobes, connected by a thin isthmus; a small pyramidal lobe extending cranially from the isthmus is seen in a minority of cases.

Topographically, the gland lies in the anterior inferior neck, anterior and on either side of the trachea. Anterior to the gland are the thin strap muscles-sternohyoid, sternothyroid and omohyoid- and anterior-lateral, the more bulky sternocleidomastoid muscles. Lateral to each thyroid lobe are located the common carotid artery and the internal jugular vein. Posterior to each thyroid lobe and anterior to the vertebrae lies the longus colli muscle. Behind the trachea and the thyroid lobe, usually the left one, the cervical oesophagus is seen.

In adults, the thyroid lobe dimensions are about 4-6 cm in length and 1.3-1.8 cm in anteroposterior and transverse diameter and the isthmus up to 3 mm in thickness.

Thyromegaly is present when the anteroposterior diameter of the lobes exceeds 2 cm and of the isthmus, 4 mm.

Sonographically, the normal thyroid has a homogenous echopattern, hyperechoic compared to the neck muscles. The trachea is seen as an echogenic convex line, with a large acoustic shadow produced by air, which obscures the posterior wall of the trachea and the vertebral body behind it. The adjacent muscles are hypoechogenic with echogenic fibrous lines; the vessels are anechogenic with well defined walls. The jugular vein is easily compressible by a light pressure. The carotid artery is non compressible and pulsatile. Typical bowel layers are seen in the oesophagus. On colour or power Doppler sonography, flow is seen scattered

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throughout the gland in a degree similar to other superficial solid organs such as testes [Figure 3].

Figure 3 Thyroid gland. Normal anatomy. (a) Transverse view of the thyroid gland (b) Longitudinal view of the left lobe (c) Transverse extended-field-ofview scan of the neck. (d) Transverse view of each lobe and the isthmus in a split image. Abbreviations: (T) shadowing produced by air in the trachea, (CCA) common carotid artery, (JV) internal jugular veins (JV), (S,SM) strap muscles, (SCM) sternocleidomastoid muscle, (LC) longus colli muscle, (E) oesophagus.

a)

b)

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d)

Congenital Anomalies Embryological, the thyroid gland develops at the level of the base of the tongue, starting in the 1st- 2nd week and completing in the 11th week of intrauterine life. The thyroid gland arises as an endodermal thickening at the junction of the developing anterior and posterior tongue, at the level of the foramen caecum, between the first and second branchial arches. From the lingual position, the gland descends to the lower neck pulled by the aortic sac of the heart, keeping an elongated pharyngeal connexion, the thyroglossal duct, that normally disappears in the 5th-6th week of intrauterine life.

Congenital abnormalities of the thyroid include ectopia, hypoplasia, congenital agenesis and thyroglossal duct cysts. Ectopic or "lingual" thyroid, due to a deficit in migration, occurs in about 1/100.000 individuals. It is generally diagnosed on thyroid scintigraphy (I123), most commonly seen in the midline above the hyoid bone, between the foramen cecum and the epiglottis [Figure 4].

Figure 4 Ectopic lingual thyroid. Midline sublingual I123 uptake, is seen on thyroid scintigraphy, without any uptake at the level of the normal thyroid.

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Hypoplastic and agenetic thyroids are readily evaluated by US. Unilateral hypoplasia or agenesis may result in contralateral hypertrophy. Thyroglosal duct cysts may develop in cases with residual thyroid cells in the thyroglossal duct. It is the most common of the congenital cysts in the neck, most often present in childhood, located in the middline, between the thyroid gland and the hyoid bone. Sonographically, the lesion is sonolucent with low-level intraluminal echoes [Figure 5]. As the thyroglossal cyst may represent the only remaining thyroid tissue, a thyroid radionuclear scan must be performed pre-operatively to confirm that the thyroid gland is present and normally functioning.

Figure 5 Thyroglossal cyst. A midline neck lump was palpated in this 2-yearold male child. (a) Transverse scan. (b) Longitudinal scan. A cystic mass with low-level internal echoes was demonstrated in the midline, between the thyroid isthmus and the hyoid bone.

(a)

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Focal Disease Thyroid nodules are extremely common. The incidence is directly correlated to age: the percentage of patients with nodules is approximately equal to age minus 10.

Ultrasound is an extremely sensitive tool in the detection of nodules, the incidence of detected nodular disease almost equal to that of pathologists at post-mortem autopsy [Figure 6]. Nevertheless, the incidence of thyroid cancer is very low (10-13% of thyroid nodules).

Figure 6 Incidence of thyroid nodules. Thyroid nodules incidence (x axis) increases with age (y axis). On US and autopsy nodules are detected in a similar incidence (50% and 40% of patients above 50-year-old, respectively), farther higher than on palpation.

Hyperplasia of the thyroid gland or goiter, is three times more common in females, in 80% of cases idiopathic, and in 20% related to iodine deficiency, familial causes or medications. When hyperplasia progresses to nodularity, the pathological condition is called multinodular goiter (MNG) [Figure 7].

Figure 7 Multinodular goiter. Panoramic view. Multiple nodules of variable echogenicity are seen scattered in an enlarged thyroid gland. (CA) carotid artery.

Pathologically, the nodules may be hyperplastic, adenomatous or colloid.

Sonographically, nodular hyperplasia presents variable echogenicity, hypo, iso or

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hyper compared to normal parenchyma. Cystic components are common, usually associated with internal septations and mural nodules [Figure 8].

Figure 8 Cystic components with septations in a benign goiterous nodule.

Bright foci with "ring down" or "comet tail" artifacts representing inspissated colloid, may be seen. Careful should be taken to avoid mistakes calling these colloid focus microcalcifications [Figure 9].

Figure 9 "Ring down" sign from bright foci in a mixed solid and cystic colloid nodule, representing inspissated colloid.

Macrocalcifications, in the form of peripheral "eggshell" or large internal foci, may be present [Figure 10].

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Figure 10 Patterns of calcifications in a benign thyroid nodule. (a) Peripheral "egg shell" calcification surrounding the nodule. (b) Calcifications inside the nodule.

(a)

b)

Benign follicular adenomas account for 5-10% of thyroid nodules. They are solid hypo to hyper echoic nodules, well marginated and often with a hypoechoic halo [Figure 11]. Follicular adenoma and follicular carcinoma can be differentiated only on the basis of vascular and capsular invasion. US and FNA are unable to distinguish between them and a cytological diagnosis of follicular tumour should be followed by surgical resection.

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Figure 11 Follicular adenoma. Well-marginated homogeneous hypoechogenic nodule, surrounded by a hypoechogenic halo.

Thyroid cancer represents <1% of all malignancies and mortality from thyroid cancer is about 0.5/100.000, with a 4-8% 20 years cumulative mortality. A 2.4-fold increase in the diagnosis of thyroid malignancy in the last thirty years with a stable mortality rate indicates that changes in the diagnostic approach of thyroid nodules has resulted in an increased detection of sub-clinical disease. The most common histological diagnosis is papillary, accounting for more than 75%, followed in frequency by follicular, medullary, anaplastic and Hurtle cell cancer. Papillary cancer is the most common type in younger than 40 years and in females, has an excellent prognosis, with a 90-95% survival at 20 years. It is multifocal in 20% of cases and grows slowly. Lymphatic dissemination to the cervical lymph nodes is often present at diagnosis, without affecting the good prognosis. Sonographically, papillary tumours are typically solid, hypoechoic and frequently with microcalcifications. Lymph node metastasis may also contain microcalcifications and cystic degenerative areas [Figure 12].

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Figure 12 Papillary thyroid cancer. Examples of patterns in different cases. (a) Hypoechoic poorly marginated solid lesion. FNA under US guidance was performed (arrow). (b) Complex lesion, solid with internal cystic components. (c) Metastatic jugular lymphadenopathy with microcalcifications. (d) Metastatic jugular lymphadenopathy with microcalcifications and cystic changes. (e). Hypervascularization in a thyroid tumour, seen on Power Doppler.

(a)

(b)

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(c)

(d)

(e)

Follicular cancer represents about 10% of thyroid malignancies, and is divided into minimally and widely invasive forms. It is indistinguishable sonographically and by FNA cytology from adenoma. Thus, any follicular lesion has to be resected for histological examination. It appears as a solid, hypoechogenic, sometimes with a cystic component [Figure 13]. Unlike papillary cancer, follicular cancer spreads hematogeneously to bone, brain, lung and liver.

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Figure 13 Follicular thyroid cancer. Examples of patterns in different cases. (a) Hypoechoic homogeneous solid lesion, peripheral to central vessels â&#x20AC;&#x153;spoke-and-wheel-likeâ&#x20AC;? appearance. (b) Hypoechoic lesion with a large cystic component.

(a)

(b)

Medullar cancer accounts for 5% of thyroid malignancies. It secrets calcitonin and in 10-20% of cases is associated with multiple endocrine neoplasia type II. The sonographic appearance is similar to the papillary carcinoma one. Anaplastic cancer accounts for less than 5% of thyroid cancers. It is more common in patients older than 60 years old, and has a dismal prognosis. It usually appears as a large, solid, hypoechoic mass. Local invasion of adjacent structures is common. Thyroid lymphoma represents less than 5% of thyroid tumours, and metastases, most commonly from lung, breast and renal cell cancers are very unusual.

The sonographic appearance of benign and malignant nodules overlap and thus, sonography is unable to determine with assurance if a nodule is benign or malignant.

Nevertheless, there are sonographic findings in favour of benign and malignant nodule. These are summarized in Table 1.

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Table 1 Differentiation of Thyroid Nodules by sonographic characteristics Benign characteristics Simple cysts Cystic components Hyperechogenic/Isoechogenic Gross calcifications/Eggshell calcification Thin peripheral halo

Malignant characteristics Solid Hypoechogenic Microcalcifications No halo or thick peripheral halo

FNA (fine needle aspiration) cytology of thyroid nodules is indicated in nodules with malignant characteristics, in patients with a history of MEN II, previous neck radiation or thyroid resection and in the presence of cervical lymphadenopathy suspicious for metastatic disease. Solid solitary nodules should be biopsied when the diameter exceeds 1.5cm and mixed solid and cystic, when exceeding 2 cm. Ultrasound-guided FNA is an established technique for the diagnosis of thyroid malignancy.

Diffuse Disease Hashimoto's thyroiditis (chronic immune lymphocytic thyroiditis), the most common cause of hypothyroidism, is due to autoantibodies to thyroglobulin. The gland is normal or enlarged and hypoechoic, with a heterogeneous echotexture, and a multilobulated appearance due to echogenic fibrous stands and very vascular on Color Doppler. It carries a slightly increased risk of thyroid lymphoma; benign and malignant nodules may coexist with this autoimmune thyroiditis. In the end stage, the gland becomes atrophic [Figure 14].

Figure 14 Hashimoto's thyroiditis. Examples of patterns in different cases. (a) Scattered tiny hypoechoic nodules. (b) Marked hypervascularity. (c and d) Diffusely hypoechoic heterogeous gland, with hyperechoic fibrous strands. (e) End-stage hyperechogenic atrophic gland.

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Graves' disease (diffuse toxic goiter), the most common cause of hyperthyroidism, is another autoimmune disorder. The gland is enlarged, hypoechogenic, and hypervascular ("thyroid inferno") [Figure 15].

Figure 15 Graves' disease. (a) Diffusely enlarged, homogeneously hypoechoic gland. (b) Extremelly increased gland vascularity.

(a)

(b) Subacute granulomatous thyroiditis (de Quervain's thyroiditis) is caused by a viral infection, usually following an upper respiratory tract infection. Transient hyperthyroidism is followed by transient hypothyroidism. The thyroid is enlarged and painful, often with fever. Sonography shows a poorly marginated area or areas of decreased echogenicity [Figure16].

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Figure 16 Subacute granulomatous thyroiditis (de Quervain's thyroiditis). (a) and (b). Diffusely enlarged hypoechoic heterogeneous gland, with poorly defined areas of hypoechogenicity in both lobes of the thyroid gland.

(a)

(b)

Parathyroid glands Anatomy Normal parathyroid glands are usually four, two upper, located behind the middle portion of the each thyroid lobe, and two lower, behind and just inferior to the lower poles of the thyroid gland, oval in shape, 1*3*5 mm in diameter (Figure 17). They are almost never seen with ultrasound due to their small shape and insufficient acoustic difference with the surrounding tissues.

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Figure 17 Parathyroid glands. Normal anatomy. (a) Relationship of upper and lower parathyroid glands with the thyroid gland. (b) Relashionship with the larynx (voice box).

(a)

(b)

Hyperparathyroidism Primary hyperparathyroidism is a relatively common endocrine disorder (1-2/0.000), affecting patients between 40-60 years old, with a female-to-male ration of 2.5 to 1.

In about 85% of cases it is due to a solitary parathyroid adenoma, 15%, to multiple gland adenoma or hyperplasia, 1% carcinoma. It may be associated with multiple gland neoplasia (MEN) I. The diagnosis is based on clinical and laboratory findings.

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Secondary hyperparathyroidism is usually secondary to renal insufficiency. On sonography, parathyroid adenoma (PTA) is seen as an oval, hypoechoic solid mass, hypervascular on colour Doppler, located posterior to the thyroid gland, with a linear interface between the PTA and the thyroid gland [Figure 18].

Figure 18 Parathyroid adenoma. Examples of patterns in different cases. (a) Very hypoechoic solid adenoma of the lower parathyroid gland. (b) Vascularity detected on colour Doppler. (c) and (d) Large solid hypoechoic parathyroid adenoma of the upper parathyroid gland in transverse (c) and longitudinal (d) scans.

(a)

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(d)

Ectopic PTA is found in about 3% of cases, in different locations: retrotracheal and retroesophageal, in the lower neck and mediastinum, in the carotid sheath and intrathyroid [Figure 19].

Figure 19 Parathyroid adenoma in ectopic locations. (a) and (b) Intrathyroid PTA on CT and on US scans. (c) and (d) PTA in the sheath of the common carotid artery, on transverse and longitudinal view (arrows).

(a)

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(c)

(d)

A combination of sonography and scintigraphy with sestamibi for the diagnosis of PTA is routinely used [Figure 20]. Parathyroid carcinoma tends to be larger, about 35 cm in diameter, irregularly rounded, heterogeneous and usually infiltrating the surrounding tissues.

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Figure 20 Parathyroid adenoma diagnosed by Technetium 99-m sestamibi scintigraphy. (a) Early (10') image shows thyroid gland uptake, superimposed on the PTA uptake. (b) Delayed (120') image shows persistent uptake in the PTA and show out in the thyroid gland.

(a) (b) Other modalities such as CT scans, MRI, angiography and venous sampling are reserved for problem cases. US-guided FNA may be performed when the lesion is seen on sonography but not confirmed on sestamibi scan.

The treatment of choice of hyperparathyroidism is surgical removal of the enlarged parathyroid gland, carrying a cure rate of 95-98%, with a low morbidity. Accurate preoperative imaging and intraoperative parathyroid hormone monitoring is required for the performance of minimally invasive surgical techniques with unilateral neck exploration, which is the present procedure of choice.

Lymph Nodes Anatomy Lymph nodes are composed of lymphoid follicles located in the outer cortex and lymphatic channels, blood vessels and connective tissue, in the inner medulla [Figure 21].

Figure 21 Normal lymph node. Drawing showing the cortical and medullary components of the node.

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Normal lymph nodes are identified in the neck, in particular around the neck vessels, as an oval-shaped structure, long-short axis ratio of 1.5-2, with an echogenic hilum and a hypoechogenic cortex and a central vascularity [Figure 22] [Table 2].

Figure 22 Normal lymph node. An oval-shaped structure, long/short axis 1.5-2 times, hypoechogenic cortex, echogenic hilum and central vascularity is seen.

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Table 2 Characteristics of Normal Lymph Nodes Oval-shaped Long-short axis ration more than 1.5 Hypoechogenic cortex, echogenic hilum Central vascularity

Lymphadenopathy Enlarged nodes may be reactive or neoplastic. Reactive, hypertrophic or inflammatory lymph nodes are round to oval shaped, larger than 5 mm in short diameter, with a thickened homogeneously hypoechoic cortex and a preserved echogenic hilum with increased central vascularity [Figure 23]. Abscess formation is a major complication of lymphadenitis. Cervical lymphadenitis is very common in children; it is the most common cause of a pediatric neck mass, and may persist for months after adequate treatment.

Figure 23 Neck lymphadenitis. Oval-shaped lymph node, with a thickened homogenously hypoechogenic cortex, and central increased vascularity is seen.

Malignant lymph nodes are round shaped, with a short to long axis (S/L) ratio > to 0.5, generally enlarged, very hypoechoic, heterogeneous, without central hilum, and with peripheral of mixed vascularity (Figure 24).

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Figure 24 Malignant lymphadenopathy. Lymphoma. (a) Rounded lymph nodes, very hypoechogenic, without central hilum (b) Peripheral vascularity.

(a)

(b)

Metastatic lymph nodes from thyroid papillary carcinoma often present necrosis and microcalcifications [Figure 25] [Table 3].

Figure 25 Malignant lymphadenopathy. Metastatic thyroid carcinoma. Rounded hypoechogenic lymph nodes, without central hilum, and scattered echogenic foci (arrows), compatible with microcalcifications.

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Table 3 Characteristics of Neoplastic Lymph Nodes Round-shaped Long-short axis ratio less than 1.5 Absent echogenic hilum Peripheral of mixed vascularity Cystic changes, microcalcifications (thyroid)

Ultrasound-guided core needle biopsy is often necessary for the diagnosis of malignancy in suspected lymph nodes [Figure 26].

Figure 26 Ultrasound-guided core biopsy of lymph node. A 14-16 gauge long throw core biopsy needle is advanced and fired into the lesion.

Ultrasound guidance allows real time observation of the needle passage and entry into the lesion. Reverberation artifacts are seen posterior to the needle.

Salivary Glands Anatomy The parotid and submandibular glands are easily identified on ultrasound examination, as oval, medium echogenic, well delimitated structures, the parotid gland along the ramus and the submandibular, below the lower edge of the mandible [Figure 27].

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Figure 27 Normal salivary glands. (a) Submandibular gland. (b) Parotid gland.

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Enlarged salivary glands Ultrasound is performed for the differential diagnosis of an enlarged salivary gland, to determine if the cause is a generalized inflammation, sialolithiasis or neoplasms.

Stones are more common in the submandibular glands and may be intraductal, associated with a dilated duct, or intraglandular. Like stones everywhere, they appear as echogenic foci with posterior acoustic shadow [Figure 28].

Figure 28 Intraductal stone. A very echogenic structure casting an acoustic shadowing associated with an enlarged duct is seen in the submandibular salivary gland.

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Tumours are relatively rare, more common in the parotid gland and generally benign.

Pleomorphic adenoma is a benign lesion, accounting for approximately 70% of tumours. It is seen as a solid, hypoechoic, homogeneous mass [Figure 29]. Warthin's tumours are also benign, and account for approximately 10% or salivary glands tumours. They are less homogeneous than the pleomorphic adenoma, often with cystic elements [Figure 30].

Figure 29 Parotid pleomorphic adenoma. A large, homogeneous hypoechoic mass is seen in the parotid gland.

Figure 30 Parotid Warthin's tumour. A large, heterogeneous mass is seen in the parotid gland.

Neck Vessels Carotid Arteries Carotid sonography with Doppler capabilities is nowadays considered the first and often the sole examination to evaluate the carotid arteries.

The normal carotid arteries are rounded, sonolucent, with a bilayered appearance of

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the wall, of less than 0.8 mm thickness [Figure 31].

Figure 31 Normal carotid artery wall. Normal intima-media thickness measured between the interfaces blood-intima and media-adventitia (arrows).

The normal flow in the internal carotid artery (ICA), which supplies the brain, is a lowresistance flow, with broad systolic peaks and maintained diastolic flow [Figure 32].

Figure 32 Normal internal carotid artery flow. Low resistance waveform characterized by a broad systolic peak and well maintained diastolic flow.

The normal flow in the external carotid artery (ECA), which supplies the muscles and skin of the neck, face and scalp, is a high resistant flow, with sharp systolic peaks and low or absent diastolic flow (Figure 33).

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Figure 33 Normal external carotid artery flow. High resistance wave flow characterized by a sharp systolic peak and low diastolic flow.

The normal flow in the common carotid artery (CCA) has characteristics of both branches, although, due to the larger flow directed to the internal carotid artery- in the range of 70-80%- tends to mirror the flow in the internal carotid artery [Figure 34].

Figure 34 Normal common carotid artery flow. Intermediate resistance wave flow, in-between ICA and ECA flow, although nearer ICA flow.

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Further differences between ICA and ECA are summarized in Table 4.

Table 4 Main differences between ICA and ECA ICA

ECA

Posterior/Lateral Larger diameter No branches Low resistance flow

Anterior/Medial Smaller diameter Yes branches High resistance flow

A carotid ultrasound study is aimed to identify atherosclerotic changes, mainly intimamedia thickness and plaques, and the Doppler component, to determine the severity of carotid stenosis. The criteria for the classification of ICA stenosis is based in the peak systolic velocity (PSV), ICA/CCA velocity ration and end diastolic velocity (EDV) [Table 5].

Table 5

Criteria for Diagnosis of ICA Stenosis Primary Parameters %Diameter PSV (cm/sec) Stenosis

Additional Parameters

Plaque estimate (%)

ICA/CCA PSV Ratio

ICA EDV (cm/sec)

Normal

< 125

_

<2

< 40

<50

< 125

< 50

<2

< 40

50-69

125-230

> 50

2-4

40-100

70-near occlusion

> 230

> 50

>4

> 100

Variable

Variable

Near occlusion

Total occlusion

High, low or undetectable _

Visible No detectable

_

_

Carotid Artery Stenosis: Gray-Scale and Doppler US Diagnosis. Society of Radiologists in Ultrasound Consensus Conference. Radiology 229: 340-346; 2003

Flow velocity increases rapidly when the stenosis is larger than 50%. At critical stenosis (>95% stenosis), flow velocities may decrease. Total occlusion causes loss of flow, but very tight stenosis can diminish flow to an undetectable level [Figure 35].

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Figure 35 Relationship between % decrease in lumen diameter (x axis) and flow velocity (y axis).

Spencer MP, Reid JM. Quantitation of carotid stenosis with continous wave Doppler ultrasound. Stroke 1979; 10: 793-8

Further imaging studies, like CT angiography or MR angiography are needed for the differentiation between critical stenosis and occlusion, since a very tight stenosis is still a surgically treated pathology, as opposite to total occlusion.

Different degrees of carotid stenosis and occlusion are exemplified in Figures 36-40.

Figure 36 Mild stenosis (<50% ICA diameter stenosis) A small plaque is seen in the proximal ICA ( arrow). Systolic (111 cm/sec) and diastolic (33.4 cm/sec) flow velocities are within normal limits.

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Figure 37 Moderate stenosis (50-69% ICA diameter stenosis). Peak systolic velocity is elevated to 157 cm/sec and EDV to 55 cm/sec.

Figure 38 Severe stenosis (>70%) ICA diameter stenosis) Peak systolic velocity is elevated to 284 cm/sec and end diastolic velocity, to 110 cm/sec.

Figure 39 Critical stenosis (>95%) ICA diameter stenosis). Examples in two patients. (a) "String sign" critical stenosis of the artery diameter (arrow). (b) Peak systolic velocity dropped due to the high resistance in the carotid artery.

(a)

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(b) Figure 40 Occlusion. No flow is detected in the ICA.

Ultrasound may be useful to characterize atheromatous plaques. A homogeneous plaque tends to be stable, but an inhomogeneous plaque, sometimes with internal hemorrhage or ulceration, is unstable, prone to rupture and embolization [Figure 41].

Figure 41 Ulcerated plaque. "Intraplaque flow" with colour Doppler, characteristic appearance of ulcerated plaque.

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Vertebral Arteries The vertebral arteries are seen crossing between the transverse processes of the cervical spine. The patency and direction of flow may be determined by US-Doppler colour, and the flow characteristics, by spectral Doppler. The vertebral wave forms are similar to the ICA [Figure 42].

Figure 42 Normal vertebral artery flow. Low resistance flow in the vertebral artery. Note the acoustic shadows from the transverse processes (arrows), resulting in segmental visualization of the vertebral arteries.

Reversed flow compared to flow direction in the CCA indicates severe stenosis or occlusion at the level of the origin of the subclavian or innominate arteries (Figure 43).

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Figure 43 Reversed vertebral artery flow. "Subclavian steal", characteristic of severe stenosis or occlusion at the level of the origin of the subclavian or innominate arteries. (a) Flow in vertebral artery. (b) Flow in common carotid artery.

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Jugular Veins The normal internal jugular vein runs lateral and anterior to the carotid arteries. The flow wave form is pulsatile due to the proximity of the veins to the heart. The vein is easily compressed [Figure 44].

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Figure 44 Normal jugular vein. (a) Sonolucent and compressible lumen. Right plot, before compression. Left plot: after compression. (b) Pulsatile wave flow.

(a)

(b)

A continuous flow indicates proximal obstruction. Lack of flow and uncompressibility of the vein, often with a low echogenic lumen is indicative of thrombosis [Figure 45].

Figure 45 Thrombosed jugular vein. (a) Echogenic and uncompressible vein Right plot, before compression. Left plot: after compression. (arrows). (b) Flow void on Doppler.

(a)

Ultrasound of the Neck Gaitini

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(b)

Recommended reading 1. Gaitini D, Evans RM and Ivanac G. Thyroid Ultrasound. In: Dietrich CF. EFSUMB Course Book on Ultrasound, London 2012, pp. 461-524.

2. EFSUMB Cases of the Month (www.efsumb.org).

3. Baskin HJ. Ultrasound of thyroid nodules. In: Baskin HJ, editor. Thyroid ultrasound and ultrasound-guided FNA biopsy. Boston: Kluwer Academic Publisher, 2007: 71-86 4. Thyroid and Parathyroid Ultrasound Examination Guideline (AIUM in conjunction with ACR, SPR and SRU), 2013 (www.aium.org).

5. Gritzman N, Quis SA, Evans RM and Ivanac G. Sonography of the salivary glands and soft tissue lesions of the neck. In: Dietrich CF. EFSUMB Course Book on Ultrasound, London 2012, pp. 475-500.

6. Gaitini D, Soudack M. Diagnosing carotid stenosis by Doppler sonography: state of the art. J Ultrasound Med. 8:1127-1136, 2008