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ULTRASOUND OF THE NECK
RADIOLOGIC EVALUATION OF THE NECK
0033-8389/00 $15.00
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ULTRASOUND OF THE NECK Dietmar Koischwitz, MD, and Norbert Gritzmann, MD
High-resolution B-mode sonography has improved in the past few years and has become a very valuable tool in the diagnosis of diseases of the head and neck. Sonography is commonly the first imaging modality after clinical examination. It is easily tolerated by patients and is inexpensive. It provides valuable diagnostic information with a high degree of diagnostic accuracy. On the basis of the sonographic findings, selection of additional imaging modalities including CT and MR imaging can be applied more judiciously. This article provides the most up-to-date information about the indications, findings, and limitations of high-resolution B-mode sonography in the evaluation of head and neck pathology. INSTRUMENTATION Optimal ultrasound (US) examination of the superficial structures of the head and neck requires appropriate equipment with highresolution small-parts transducers that make use of high-frequency US. US sequences between 5 and 20 MHz are used (most commonly 7.5 to 10 MHz). Either the transducer is placed directly on the skin or a silicon stand-off pad is placed between the transducer and the skin to get ideal contact with the surface, especially in the angle of the jaw and the neck. High-frequency small-parts sonography, using frequences between 5 and 10
MHz, is used for the near field; this allows an axial resolution of 0.5 mm or less and a lateral resolution of 1 mm or less. The spatial resolution improves when high frequencies (15 to 20 MHz) are used, which provide nearly microscopic resolution of small areas.35 EXAMINATION TECHNIQUE A systematic examination protocol is mandatory for the evaluation of the head and neck. It begins with the examination of the thyroid gland where the instrument is adjusted and frequency and gain are optimized. The examination is continued along the vascular sheath to the floor of the mouth, tongue, and the salivary glands and tonsils. The next step is to examine the status of the lymph nodes including nuchal, accessory, and transverse cervical nodes. If clinically indicated, the larynx and cervical esophagus are also evaluated.18,35
CERVICAL LYMPH NODES The majority of the normal lymph nodes in the head and neck show an axial diameter of 2 to 5 mm with the exception of the jugulodigastric and the jugulo-omohyoid lymph nodes, which are larger and reveal an axial diameter of 8 to 10 mm, and a longitudinal diameter of 15 to 20 mrn.lo,15,35 Normal lymph
From the Central Department of Radiology, Siegburg Hospital GmbH, Siegburg, Germany (DK); and the Departments of Radiology and Nuclear Medicine, Hospital of the Brothers of St. John, Salzburg, Austria (NG)
RADIOLOGIC CLINICS OF NORTH AMERICA VOLUME 38 * NUMBER 5 SEPTEMBER 2000
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nodes are difficult to detect because of their high echogenicity, which is similar to that of the surrounding fatty tissue. They can only be demonstrated by the use of high frequencies (13 MHz)." Diseases of the lymph nodes lead to an increase of fluid either by swelling of the histiocytes in the sinus, by hyperplasia of lymph follicles, or by invasion of tumor cells. As a consequence, this results nearly always in enlargement of the lymph nodes and a reduction of the e~hogenicity.~~
REACTIVE LYMPH NODES
Enlarged reactive lymph nodes are the most frequent sonographically encountered entities in the head and neck in nonselected patients. Some reactive lymph nodes are found in nearly every patient, most commonly the submandibular and lateral cervical nodes. The reactive enlargement of the lymph nodes is the response to past inflammatory disease and is reflected bv histiocvtosis in the lymph node sinus. The typical sonographic appearance shows a longitudinal-to-oval shape with rounded poles and a smooth border. The echogenicity is low and homogeneous with a hyperechoic peripheral or central band, consisting of the lymph node hilus with fat and small vessels (Fig. 1).The axial diameter is usually less than 8 mm, whereas the longitudinal diameter can range from 15 to 20 mm.2
Figure 1. Reactive-hyperplastic lymph nodes, left lateral cervical. Hypoechoic structure with moderate enlargement, smooth border, and preserved eccentric hyperechoic hilus.
Figure 2. Acute nonspecific lymphadenitis, left submandibular. Craniocaudal section. Round spherical and ovalshaped hypoechoic lymph node with a smooth border and hilus not detectable.
INFLAMMATORY LYMPH NODE DISEASE
In acute, nonspecific lymphadenitis the lymph nodes are painful and markedly enlarged. Their shape is longitudinal or ovoid with rounded poles. In addition, they may be round to spherical with smooth borders and display a hypoechoic appearance. The hilus of the lymph node is not always apparent. The differentiation from the surrounding soft tissues and from other lymph nodes, however, is mostly discernible (Fig. 2). The enlargement of acute inflammatory lymph nodes ranges from 20 to 25 mm in longitudinal diameter; however, it should be emphasized that the absolute measurements of the size of a lymph node, such as the longest diameter, is not sufficient for differentiation of inflammatory from metastatic lymph nodes. Different authors'6,42 have shown that the ratio between longitudinal and transverse diameter of a lymph node (longitudinal-trunsverse diameter ratio), also known as the shortto-long-axes ratio, or the maximal-transverse quotient, also known as roundness index (RI), has a higher degree of accuracy in the differentiation between inflammatory and metastatic lymph nodes. A RI greater than 2 (longitudinal shape) indicates inflammatory disease in 84%, whereas a RI less than 1.5 (spherical shape) favors metastatic involvement in 71% of cases.47 In subacute inflammation the lymph nodes
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echogenic subcutaneous fatty tissue and muscles. PRIMARY LYMPH NODE DISEASES
Figure 3. Specific lymphadenitis (tuberculosis) in the upper third of the right lateral cervical group. Spherical shape with irregular border and with central necrosis of the involved lymph node. Adjacent to it are four smaller reactive lymph nodes.
tend to become smaller. This can be well documented by sonography. The shape remains longitudinal, the borders are smooth, and the internal architecture is less hypoechoic. The lymph node demonstrates small spots and stripes and the echogenic hilus is visible. In chronic inflammation, after weeks and months, when the clinical symptoms have subsided, the lymph nodes can still be detected by sonography. They are small, soft, movable, slightly hypoechoic with smooth borders, and have a longitudinal shape.
Sarcoidosis (Boeck's disease) is a benign granulomatous disease of the lymph nodes, whereas Hodgkin's and non-Hodgkin's lymphomas are aggressive malignant lymph node neoplasms. Both reveal sonographically similar and overlapping features. In nearly every case multiple lymph nodes are involved (e.g., one or two regional groups), which result in conglomeration of the enlarged lymph nodes. The individual nodes are round to oval in shape. A solitary involvement of only one lymph node is rare. On sonography these lymph nodes demonstrate a round-to-spherical shape, and occasionally very large lymph nodes reveal low echogenicity or appear nearly nonechoic, simulating a cyst. Sometimes there are tiny echogenic foci in the nonechoic structures of the lymph nodes (punctate echo structure). The borders are smooth and the differentiation between the involved lymph node and the surrounding tissues is clearly delineated (Fig. 4). In cases with rapid, aggressive growth of malignant lymphomas perinodal edema may occur. Extranodal spread with infiltration of surrounding tissues rarely occurs. In sarcoidosis the lateral cervical lymph nodes and transverse supraclavicular lymph nodes are frequently involved bilaterally, as well as, occasionally, the intraglandular pa-
SPECIFIC LYMPHADENITIS
Specific lymphadenitis is principally caused by tuberculosis. The involved lymph nodes are commonly large, painless, or slightly painful under pressure. There is a significant discrepancy between the individual involved lymph nodes, with a spectrum ranging from large, round, nonechoic, to cystic-necrotic nodes with blurred borders. The surrounding uninvolved lymph nodes appear 66 Edema in the reactive and hyperpla~tic.~, surrounding tissue adjoining the tuberculous lymph node mass imparts a blurred appearance to the borders of the lymph nodes (Fig. 3). Inflammation in the surrounding tissues with the formation of fistulas may ensue in cases with nodal necrosis, abscess formation, and perforation of the capsule of the lymph nodes. Fistulas appear as hypoechoic or nonechoic linear stripes and contrast with the
Figure 4. Malignant B-cell lymphoma. Manifestation in the right lateral chain. Hypoechoic structure, smooth border, no extranodal tumorous spread, with a deformity and flattening against each other. Facet formation sign.
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rotid lymph nodes. In Hodgkin’s disease or non-Hodgkin’s lymphoma the involved lymph nodes are located most commonly posterior to the sternocleidomastoid muscle, whereas metastases from squamous cell carcinoma are localized more frequently in front of the sternocleidomastoid muscle. When rapid growth of the lymph nodes occurs in the early stages of malignant lymphoma extranodal expansion may occur late leading to deformation and flattening of the lymph nodes against each other, referred to as the facet formation sign.39In B-mode sonography echogenic lines or double lines are demonstrated between the enlarged lymph nodes. They represent encased, but not infiltrated, small vessels (small-vessel sign).36This is analogous to the sandwich-sign of the mesenteric vessels in the upper abdomen. LYMPH NODE METASTASES
Cervical lymph node metastases in the head and neck region are caused by squamous cell carcinoma in 80% of cases. Characteristic sonographic findings of metastatic lymph node disease are enlargement with a round-to-spherical shape. Commonly they are hypoechogenic, occasionally inhomogeneously echogenic, with a loss of the hilar definition. In cases of extranodal spread with infiltrative growth, the borders are poorly defined.2,13. 16. 19. 29,47,48,53,58,61,67 Common findings of metastases from squamous carcinoma are extranodal spread and central necrosis together with liquid areas in the lymph nodes 68 Lymph node metastases from ma(Fig. 5).67, lignant melanoma and papillary thyroid carcinoma have a nonechoic, nearly echo-free appearance, mimicking a cystic lesion. The sonographic diagnosis of lymph node metastases from thyroid carcinoma is more difficult than the diagnosis of metastases from squamous cell carcinoma. In some metastatic thyroid carcinomas the tumor cells infiltrate and invade the lymph node only partially and peripherally with no increase in the nodal size. Metastases of medullary and papillary thyroid carcinomas may show small punctate calcifications, referred to as psammoma bodies. The metastases may have increased vascularity. By applying color-coded duplex sonography (CCDS) it is possible to demonstrate the pathologic increased vascularity even in small lymph node metastases of 3 to 4 mm in diameter. On B-mode sonog-
Figure 5. Lymph node metastasis from squamous cell carcinoma of hypopharynx-left cervical-lateral. lntranodal necrosis.
raphy these small metastatic nodes show a hypoechogenic cystic appearance. On CCDS the number of visible vessels is disproportionally high relative to the small nodal size. Sensitivity of US in the diagnosis of cervical lymph node metastases is approximately 89% to 95%,16,19whereas specificity is about 80% to 95%.19* 56, 61 The lower percentage of specificity by US is accounted for by the difficulties in differentiating between enlarged nodes of reactive lymphoid hyperplasia and enlarged metastatic nodes. The round-to-spherical shape of the nodes is the most important criterium in the diagnosis of metastatic lymph node disease, which is clearly expressed in the RI.47, 58 Nevertheless, the sonographic differentiation between benign and malignant lymph nodes can be very difficult because of the overlap in the echogenic features and the shape of the pathologic nodes. The relationship of large lymph node metastases and tumoral invasion of the large vessels can be optimally assessed by sonography. Infiltration of the carotid arteries occurs in less than 15% of cervical metastatic lymph nodes. A direct sign of tumorous infiltration of the vessel (to the level of the media) is the conversion of the normally echogenic wall of the carotid artery to a hypoechogenic wall, which is demonstrated in 90% of cases.25,31 The length of the circumferential contact with the tumor is diagnostically significant. The probability of invasion of the wall of the artery increases when tumor covers a length of over 3.5 cm and when the circumferential encasement is over 150 degrees (Fig. 6). In the last few years
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Figure 6. Large metastatic lymph node tumor from small cell carcinoma of bronchus. A, Transverse; 6,longitudinal section. The length of contact between tumor and the common carotid artery is 5 cm. In transverse section the common carotid artery is encased by more than 150". Hypoechoic transformation of the otherwise echogenic wall of the artery. A tumorous infiltration into the vessel wall must be assumed.
different authors have used CCDS or power Doppler sonography for differentiation of di54, 56 by classifying verse lymphaden~pathies~~, lymph node perfusion. This has remained up until now more subjective because of lack of 54, 56 reliable objective criteria.51, In reactive lymph nodes a central linear or central hilar increased perfusion is found. In acute lymphadenitis a subjective recognizable, sometimes massive increased perfusion is found and the vascular architecture is preserved (color Fig. 7A). A missing or weak perfusion correlates with chronic inflammation but also with metastases. In metastatic squamous cell carcinoma different patterns of perfusion are found including peripheral increased perfusion, focal absence of perfusion (color Fig. 7C), absence of central vessels, displacement of vessels, or a chaotic irregular pattern of perfusion (color Fig. 7B). Highresistance indices or a high variation of the resistance index in the involved lymph nodes is regarded as a sign of metastatic involvement.19,56 The technologic possibilities for measurement of resistance indices in small, borderline lymph nodes of 6 to 8 mm diameter, however, are limited. In malignant lymphomas increased perfusion is found with preservation of the architecture of the vessels, similar to the findings in acute inflammatory disease (Fig. 70).57The classification of lymph node perfusion is very subjective and not applicable as a single method for differentiation
of the various lymphadenopathies. Increased perfusion can be found in malignant lymphomas and in inflammation. On the other hand, a reduction of perfusion can occur in regressive alterations of lymph nodes and in metastatic involved lymph nodes. There has been no progress in the use of contrast medium in sonographic differentiation of lymphadenopathies. The arrangement of intranodal vessels and their diagnostic analysis are noncontributory even though they are better delineated. US-guided fine-needle aspiration biopsy is recommended for histologic differentiation of the various lymph node path~logies.~,l4 Today it is still the best and most accurate method for the diagnosis of lymph node metastases. Nonpalpable lymph nodes can be punctured under sonographic guidance.52 Sensitivity, specificity, and positive and negative predictive value are reported in the literature with percentages between 95% and 980/o. 53, 59, 60 .st
PRIMARY SOFT TISSUE TUMORS
Hemangiomas and Lymphangiomas These lesions occur most commonly during the first 2 years of life or even in utero. They are divided into capillary or cavernous and are multicystic, fluid-filled cavities. The echogenicity is variable and depends on the size
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Figure 7. Lymph node perfusion. A, Lymphadenitis. Oval-shaped lymph node in the parotid gland with hilar perfusion running out of the eccentric hilum. 6,Lymph node metastases of an epithelial carcinoma in the accessory group. Spherical hypoechoic lymph node with chaotic perfusion. C, Lymph node metastasis of a papillary carcinoma of the thyroid gland, cervical-lateral. Cystic area in the lymph node and a striking increased perfusion in a septum. Illustration continued on opposite page
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Figure 8. Cystic lyrnphangioma. Transverse submental section. Multiple cystic communicating spaces filled with hypoechoic fluid.
Figure 7 (Continued). 0,Non-Hodgkin's lymphoma. Threedimensional power angio mode showing increased wellarranged hilar vascularization.
of the cystic component. They can be hypoechoic or more or less isoechoic, but usually are hyperechoic compared with the surrounding cervical soft tissues. They are highly c~mpressible.'~ Cystic lymphangioma (hygroma) can be firm and elastic, so that palpation often suggests a lipoma; however, sonographically the nonechoic cystic appearance is diagnostic (Fig. 8). CCDS helps to detect the perfusion in hemangiomas and confirm the vascular nature of the lesion.
ease, and neurinomas after amputation or operation are commonly located in the dorsolateral parts of the neck behind the sternocleidomastoid muscle. They show a hypoechogenic pattern with a smooth capsule (Fig. 10). Sometimes degenerative cystic changes occur. In some cases it is possible to demonstrate the continuity of the neurinoma with the nerve, which shows a spindle-shaped thickening at the junction between the nerve and the tumor.
Lipomas Most lipomas have an ovoid shape; are located superficially in the subcutaneous tissues; and are soft, elastic, and compressible. Pure fat-containing lipomas are rare and are relatively h y p o e ~ h o g e n i c The . ~ ~ more common fibrolipomas have a high echogenicity with a typically striated, feathery appearance (Fig. 9). Neural Tumors Neurofibromas, s c h w a ~ o m a s ,Or multiple neurofibromas in von Recklinghausen's dis-
Figure 9. Lipofibroma, infraparotid left. Elliptical hypoechoic tumor with some echogenic stripes caused by fibers.
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mass at the carotid bifurcation with increased 32 va~cularity.'~, ABNORMALITIES OF THE CERVICAL VESSELS
Figure 10. Schwannoma. Craniocaudal section, left cervical-lateral. Medium hypoechoic structure of an ovalshaped tumor with smooth borders between sternocleidomastoid muscle and common carotid artery.
Aneurysms, elongation, and tortuosity of the carotid arteries can cause tumorlike swellings in the neck that can be mistaken for a tumor or a lymph node lesion.40, They usually manifest as a pulsatile neck mass. A partially thrombosed aneurysm of the carotid artery is rare but may simulate a tumor. Bmode sonography is capable of delineating an aneurysm or tortuous carotid arteries (Fig. 12). The additional use of CCDS clarifies the diagnosis and differentiates nonperfused material in an aneurysm from perfusion of a tumor.
TUMORS OF THE CAROTID BODY (CHEMODECTOMAS)
CYSTIC LESIONS
Carotid body tumors are typically localized within the carotid bifurcation or adjacent to the carotid arteries with displacement of the internal and external carotid arteries. These tumors are highly vascular, which can usually be demonstrated by B-mode sonography (Fig. 11).CCDS displays the mass and its vascularization. The diagnosis of a carotid body tumor is based on the sonographic findings of a
Cystic lesions in the head and neck are not uncommon. The frequency of cysts in the head and neck is in the range of 1%to According to publications in the literature there are more than 20 different cystic entities.21,27* 69 The most common cysts originate from the thyroid gland, the thyroglossal duct, and branchial clefts, followed by cystic lymphangiomas. The remaining cystic lesions include ranula, dysodontogenetic cysts, lar-
Figure 11. Chemodectoma in the left carotid bifurcation. A, Transverse section. Solid inhomogeneous tumor with substantial vascularization. 6,Craniocaudal section. Encasement of the carotid bifurcation with spread of the vessels. ACI = internal carotid artery, ACE = external carotid artery, ACC = common carotid artery.
ULTRASOUND OF THE NECK
Figure 12. Fusiform aneurysm of the common carotid artery with partial thrombosis. Arrows mark the outline of the aneurysm.
yngoceles, and so forth. In patients with metastatic squamous cell carcinoma of the neck necrotic lymph node metastases may mimic a cyst.
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variable echogenicity. They can be echo-free, but most of the cysts are moderately echogenic and homogeneous, revealing a very fine granular echo pattern caused by cellular debris or crystals of cholesterol within the cyst fluid.4,27 The echo pattern usually is more heterogeneous and echogenic when concomitant inflammation exists (Fig. 14A). Reactive hyperplastic lymph nodes can be found in the adjoining soft tissue structures. In some cysts there is an interface between the echo-free fluid and the echogenic material (composed of cellular debris and crystals) in dependent positions. The sediment material can be mobilized by exerting intermittent pressure with the fingertips on the cyst wall, differentiating debris from solid tissue in the cyst wall. Power sonography differentiation of inflammation of cysts from inflammation of adjacent lymph nodes by the lack of perfusion in cysts. In the rare cases with development of a carcinoma in a branchial cleft cyst B-mode sonography can demonstrate the solid tumor component in the cyst (Fig. 14B) and Doppler sonography can confirm tumor vascularization.
Thyroglossal Duct Cysts
Thyroglossal ducts cysts are located in or near the midline of the neck, between the f m m cecum ~ ~ of the tongue base and the pyramidal lobe of the thyroid gland. They are most commonly located at the hyoid bone and in most cases there is a connection between the cyst and the hyoid bone.', On sonograms the thyroglossal duct cyst appears as a typical cystic lesion, nonechoic or hypoechoic with posterior acoustic enhancement and well-defined margins. Occasionally they are multicystic and contain solid components of echogenic thyroid tissue (Fig. 13).In case of infection the cyst becomes painful and the fluid in the cyst displays inhomogeneous echoes from pus. In 1%of thyroglossal duct cysts a carcinoma may develop, usually a papillary adenocarcinoma. In such cases the cyst increases in size and solid tumor tissue fills out the cystic lumen.
Epidermoids and Derrnoids (Dysodontogenic Cysts)
Epidermoids or dermoids are mainly localized in the midline of the tongue and the floor of the mouth. They are caused by epidermoid cell inclusions during the process of fusion of the branchial arches. These cysts are
Branchial Cleft Cysts
Branchial cleft cysts are located most comregi0nTventrolatmonly in the lateral era1 to the carotid bifurcation. They develop from the first or second branchial clefts with
Figure 13. Thyroglossal duct cyst. Craniocaudal section. C = cyst with solid components and with close relation to the hyoid bone (OH).
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Figure 14. Branchial cleft cyst. A, Craniocaudal section. Inflammation of the cyst. Moderate hypoechoic fluid is present with concomitant lymphadenitis (LK). 6,Craniocaudal section. Carcinoma in a branchial cleft cyst. Mostly solid tissue in the cyst.
often highly echogenic because of the increased acoustic impedance of fluid, sebum, or hairs in the lumen (Fig. 15). The change in shape of these echogenic cysts during speaking, swallowing, and tongue movement can be demonstrated sonographically and thereby exclude a solid tumor. Ranula Ranula is a cyst in the floor of the mouth of variable size and shape, caused by obstruction of sublingual ducts. Occasionally they
can become large and lead to deformity of the floor of the mouth. They can plunge caudolaterally over the posterior margin of the mylohyoid muscle or bulge in a dorsal direction with consequent difficulties in speaking and swallowing. In the case of an intraglossal location clinical differentiation from a tumor may be difficult. Sonography demonstrates a cystic, nonechoic or hypoechoic lesion, or occasionally a more echogenic lesion secondary to intracystic cellular debris. The margins are smooth and sometimes septations are found. During chewing, eating, and swallowing the cyst changes its shape and tends to bulge caudolaterally. Laryngoceles Laryngoceles are dilatations of the samle of the laryngeal ventricle of Morgagni. They can contain mucous, saliva, or air. They are classified as internal, external, and combined dependent on their location relative to the larynx. Most common symptoms are hoarseness, stridor, dysphagia, and swelling in the neck. If calcification of the thyroid cartilage does not interfere US may visualize a fluid-filled laryngocele as an echo-free, welldefined structure inside the thyroid cartilage (internal laryngoceles) and at the level of the thyrohyoid membrane (combined type) (Fig. 16).5 SALIVARY GLANDS
Figure 15. Epidermoid cyst in the tongue. Transverse section. Epidemic cyst with internal horn dandruffs. M MH = mylohyoid muscle.
The parotid, the submandibular, and the sublingual glands can be visualized sono-
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Sjogren’s Syndrome
In advanced cases of autoimmune sialadenitis sonography visualizes multiple cystic lesions caused by parenchymal destruction along with dilatation of the intraglandular ducts.9The remaining parenchyma is inhomogeneous and hypoechoic. With color Doppler sonography hypervascularization of the gland parenchyma can be demonstrated in 50% of patients (parotid inferno).50The increased vascularization of the involved gland correlates with the severity of the parenchymal changes. Sarcoidosis of the Parotid Glands Figure 16. Laryngocele. Transverse section of the larynx. A cystic saccule is found in the larynx and in the extralaryngeal right paralaryngeal space (combined type). C = laryngocele, L = larynx.
graphically. The glands are typically homogeneous echogenic structures. The intraglandular and extraglandular ducts can only be visualized sonographically by use of highfrequency, high-resolution transducers (11 MHz and higher). The facial nerve in the parotid gland most often cannot be visualized. Inflammatory disease is the most common abnormality of the salivary glands. The ratio of the different diseases of the salivary glands are estimated as sia1adenitis:sialolithiasis:sialadenosis:sialoma 100:50:10:1.15,26
The extrapulmonary manifestations of sarcoidosis affect the parotid glands in 1%to 6% and may be associated with uveitis and facial paralysis (Heerfordt’s s y n d r ~ m e )Sonogra.~~ phy demonstrates well-defined, painless enlargement of the parotid glands with a few or multiple small hypoechogenic granulomatous nodules, which are diffusely distributed throughout the glands. Sialolithiasis
Salivary stones cause painful, intermittent swelling and pain during eating. The submandibular gland is the most common site of
Acute and Chronic Sialadenitis
Acute bacterial sialadenitis occurs predominantly in elderly and debilitated patients. The salivary glands can also be involved in viral infections, including epidemic parotitis. Specific infections, such as tuberculosis or actinomycosis, are infrequent. In about 50% of cases with stones there is associated sialadenitis. In acute or chronic sialadenitis sonography demonstrates inhomogeneous hypoechogenicity of the glandular parenchyma. In acute inflammation hypoechogenicity is often more dominant than in chronic inflammation (Fig. 17). Sonographic findings occur in 18% of patients with chronic recurrent inflammation. These consist of inhomogeneous, patchy changes with duct ectasia in the parenchyma.12,28,44
Figure 17. Acute sialadenitis in the left parotid gland. Transverse section showing unilateral enlargement of the gland. lnhomogeneous hypoechoic parenchyma. Liquid-containing abscess with abscess membrane (arrows). UK = jaw.
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involvement (83%), followed by the parotid gland (13%) and, rarely, the sublingual gland S YO).^', Eighty percent of the stones are calcified and can be detected by conventional radiograph examination. Sonography has the capability to localize nonopaque stones that cannot be visualized by plain film examination. Stones are located in the glands or in the ducts. Concomitant inflammation with dilatation of the ducts occurs (Fig. 18A). The accuracy of sonography in salivary lithiasis ranges from 80% to 94%.41,45, 65 The typical sonographic appearance of a salivary stone reveals an echogenic complex with sound shadowing (Fig. 18B). Stones smaller than 2 mm in diameter may not show a shadowing. Errors in diagnosis occur in very small stones in the intraglandular ducts without ductal dilatation. Demonstration of small stones is facilitated by increasing salivary flow with the administration of a lemon stick, which leads to duct ectasia, and stones are recognized more clearly. Sialadenosis Sialadenosis is a noninflammatory, nonneoplastic, symptomatic enlargement of the salivary glands, most commonly involving the parotid glands. It is commonly associated with endocrine diseases; nutritional or metabolic states; and following administration of certain drugs (anorexia, diabetes, alcoholism, and so forth). The sonographic examination shows enlarged glands, with homogeneous,
echogenic parenchyma excluding enlargement of the glands secondary to tumor or adjoining lymph node enlargement.43,a
TUMORS OF THE SALIVARY GLANDS Salivary gland tumors constitute about 0.3% of all neoplasms. They are located in the parotid glands in 70% to 80% of cases. Pleomorphic adenomas comprise 70% to 80% of parotid tumors, whereas 5% to 10% are papillary cystadenoma lymphomatosum (Wharthin’s tumor). Tumors of the parotid glands are malignant in about 10% of cases, of the submandibular gland, in about 45%, and of the sublingual glands in about 90% of cases.46,65 Benign Tumors of the Salivary Glands Pleomorphic Adenoma
Pleomorphic adenoma is the most frequent tumor of the salivary glands (24%to 71%).43,46 The adenoma is localized in the superficial lobe of the gland in 90% and the deep lobe in about 10% of cases. The tumor is composed histologically of epithelial, myoepithelial, and mesenchymal tissues. Because of its mixed and variable composition, the sonographic appearance is also varied. The tumor is well circumscribed and reveals a homogeneous ul-
Figure 18. Sialolithiasis. A, Right submandibular gland. Hypoechoic enlargement of the gland, and ductectasias of the intraglandular ducts. lntraductal concrement with echogenic surface and dorsal shadowing (SS). B, Submandibular duct (D SM). lnhomogeneous hypoechoic structure of the submandibular gland (GL SM). Encased stone with echogenic surface and dorsal shadowing (arrows).
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trasonic pattern with decreased echogenicity and a smooth or polycyclic border (Fig. 19). Occasionally, the tumor is hyperechoic and cystic areas or calcifications may be seen. Malignant transformation of a pleomorphic adenoma occurs in 1.5%to 4.5%, which is characterized by an irregular border and an inhomogeneous, hypoechoic, or nonechoic imaging pattern. Cystadenolymphoma
Cystadenolymphoma (Wharthin’s tumor) is the most frequent monomorphic adenoma of the salivary glands. It is composed histologically of epithelial and lymphoid components. The tumor represents 2% to 24% of all tumors of the salivary glands. In 90% Warthin’s tumors are located in the superficial lobe of the parotid gland, and in 8% to 30% they occur bilaterally. Sonographically, the Wharthin’s tumor has a smooth border, is hypoechogenic, and homogeneous or inhomogeneous with cystic areas with multiple septae (Fig. ZO).43 Larger cysts appear nonechoic with posterior acoustic enhancement. Malignant Tumors of the Salivary Glands
The most frequent malignant tumors in the salivary glands are mucoepidermoid carcinoma followed by adenoid cystic carcinoma, squamous cell carcinoma, acinic cell tumor, and adenocar~inoma.~~ The histologic differ-
Figure 20. Cystadenolymphoma (Wharthin’s tumor) in the right parotid gland. Hypoechoic inhomogeneous, in part cystic tumor in the dorsal-caudal area of the gland.
entiation according to their aggressiveness results in two main groups: (1) tumors with high-grade malignancy and (2) tumors with low-grade malignancy. A histologic diagnosis cannot be established sonographically as with other imaging methods. Malignant tumors of small size (less than 2 cm) and tumors of lowgrade malignancy usually have a homogeneous sonographic pattern and smooth borders and are assessed incorrectly as benign. Tumors of high-grade malignancy and larger than 2 cm in diameter show mostly irregular borders and an internal heterogeneous echo pattern with irregular, fluid-filled necrotic areas. They present as an infiltrating mass and occasionally ipsilateral lymph node metastases (Fig. 21).63If the tumor is very large, sonography is not able to assess the infiltration into the deep surrounding structures, including the base of skull and mandible. In such cases CT or MR imaging is indispensable. Color Doppler sonography may demonstrate hypervascularity in carcinomas of the salivary glands and reveal multiple irregular vessels within the tumor. In malignant tumors there is increased vascularity along with a high arterial flow velocity.38A clear differentiation between benign or malignant tumor by means of morphologic criteria or evaluation of the perfusion is not possible in many cases. Nonepithelial Tumors of the Salivary Glands
Figure 19. Pleomorphic adenoma of the right parotid
gland. Oval-shaped, smooth, somewhat polycyclic border, hypoechoic inhomogeneous structure.
The benign tumors of the stroma of the salivary glands, such as angioma, lipoma,
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be misinterpreted as a tumor of the salivary glands.55The differentiation is easily made by US. A functional assessment is performed with measurement of the masseter muscle in a relaxed position and a strained position while biting.
INFECTION OF THE NECK, TONSILS, TONGUE, AND FLOOR OF THE MOUTH
Figure 21. Carcinoma of right parotid gland (mucoepidermoid carcinoma, high-grade type malignancy). Hypoechoic, very inhomogeneous tumor (TU) with irregular borders. Complete delineation is not possible.
neurinoma, and so forth, show a similar appearance as in other locations. The malignant nonepithelial tumors of the salivary glands including fibrous histiocytoma, malignant schwannoma, fibrosarcoma, and rhabdomyosarcoma reveal a hypoechoic pattern with irregular borders and infiltration of skin or bones. INTRAGLANDULAR METASTASES
Lymph node metastases of the parotid gland can occur, most commonly from malignant melanoma and squamous cell carcinoma of the skin and metastatic carcinoma of the breast and lung. Malignant lymphomas can involve the intraglandular parotid lymph nodes.
Inflammations in the area of the neck, tongue, and floor of mouth are not uncommon and can be caused by dental infection, tonsillitis, pharyngitis, and occasionally by foreign body perforation. US is useful for the evaluation of the extent and location of the inflammatory process and the search for an abscess cavity that necessitates surgical intervention. In phlegmon there is diffuse inflammatory edema in the neck and fascia1 spaces surrounding muscles and the great vessels. Sonographically an edematous, inflammatory, stripy collection of fluid between preformed anatomic structures is seen. Sometimes the source of the infection can be demonstrated. An abscess presents as a very painful circumscribed hypoechogenic or nonechoic, space-occupying lesion (Fig. 22). The central area of an abscess contains fluid, like pus, and can be echo free. The borders are irregular and blurred. Soft tissue remnants, vessels, or foreign bodies within the abscess cavity demonstrate echogenic reflections.
SWELLING OF SOFT TISSUES (PSEUDOTUMORS)
There is nonglandular circumscribed or diffuse swelling of the soft tissues in the neck including edema, lipomatosis, hematoma, and low-grade infection, which may mimic a tumor. They can be differentiated from a neoplasm or enlarged lymph nodes by sonography in conjunction with palpation. HYPERTROPHYOFMASSETER MUSCLES
Hypertrophy of the rnasseter I'nuscle can occur on one or both sides. Clinically, it may
Figure 22. Abscess in the base of tongue. Transverse section. Nearly nonechoic, liquid space-occupying lesion with irregular borders in the genioglossal muscle.
ULTRASOUND OF THE NECK
Aerobic bacteria may produce small bubbles of air seen as bright reflexes. TUMORS OF THE TONGUE AND FLOOR OF THE MOUTH
Benign tumors in the oral cavity are mostly papillomas of the tongue; goiter of the base of the tongue, and some mesenchymal tumors including fibroma, lipoma, or neurinoma. The most common benign tumor of the tongue in babies is hemangioma, which is most commonly congenital and causes macroglossia with a tendency to bleed. These hemangiomas can be diagnosed sonographically. They usually shrink in the course of years, which can be documented by US. This eliminates the need for MR imaging examination under anesthesia. The US pattern consists of hyperechoic areas interspersed with canalicular liquid spaces. Malignant tumors in the oropharynx represent about 5% of all malignancies. The most frequent tumor is carcinoma of the tongue. These carcinomas infiltrate the deep structures in the tongue and the oral cavity and commonly reveal ulcerations. At the time of diagnosis they are advanced and conform to stages T2 to T4 (Fig. 23).28Sonographically, cancer of the tongue presents as a hypoechogenic, inhomogeneous, space-occupying lesion with blurred borders within the echogenic intrinsic tongue muscles. Sonography can evaluate extension across the midline and infiltration of the floor of the mouth including mylohyoid muscle invasion and the relation-
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ship of the tumor to the mandible. T4 tumors often cannot be completely delineated, in particular the retropharyngeal extension and the parapharyngeal infiltration below the skull base.22-24,30
SUMMARY
Sonography, when performed by an experienced examiner, can be used for evaluation of many pathologies in the head and neck area. Some benign neck lesions, such as cysts, lipomas, carotid body tumors, and hyperplastic lymph nodes, have typical sonomorphology. Sonography has an accuracy rate of about 90% in cervical lymph node staging and can delineate subclinical lymph node recurrences. It is the method of choice for evaluation of tumor infiltrations of the wall of the great vessels. Salivary gland tumors in the superficial lobe can be delineated completely by sonography. Salivary stones can be detected and localized. Carcinoma of the tongue and floor of the mouth with T1 and T2 staging can be assessed by US. The use and contribution of color Doppler sonography for the assessment of pathologic entities in the neck is a method under clinical investigation. US-guided fineneedle aspiration biopsy of lymph nodes and tumors of the salivary glands is easy to perform and is characterized by high sensitivity and specificity. To perform US examinations of the head and neck area of the highest quality the examiner should be familiar with the anatomy of the head and neck, be informed about the clinical problem, and have experience in the interpretation of abnormal US findings. US of the head and neck area is one of the most difficult sonographic examinations and should be performed by an experienced physician.
References
Figure 23. Stage T4 carcinoma of the tongue, transverse section. Hypoechoic, in-depth infiltrating tumor (TU) with irregular borders, crossing the midline. Zunge = tongue.
Ahuja AT, King AD, King W, et al: Thyroglossal duct cysts: Sonographic appearances in adults. Am J Neuroradiol 20:579-582, 1999 Ahuja AT, Ying M, King W: A practical approach to ultrasound of cervical lymph nodes. J Laryngol Otol lll:245256, 1997 Atula TS, Grenman R, Varpula MJ, et al: Palpation, ultrasound, and ultrasound-guided fine-needle aspiration cytology in the assessment of cervical lymph node status in head and neck cancer patients. Head Neck 18:545-551, 1996 Baatenburg de Jong RJ, Rongen RJ, Lameris JS, et al:
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Evaluation of branchiogenic cysts by ultrasound. ORL J Otorhinolaryngol Relat Spec 55294-298, 1993 5. Baatenburg de long RJ, Rongen RJ, Lameris JS, et al: Ultrasound in the diagnosis of laryngoceles. ORL J Otorhinolaryngol Relat Spec 55:290-293, 1993 6. Baatenburg de Jong RJ, Rongen RJ, Lameris JS, et al: Ultrasound characteristics of thyroglossal duct anomalies. ORL J Otorhinolaryngol Relat Spec 55:299-302, 1993 7. Baatenburg de Jong RJ, Rongen RJ, Lameris JS, et al: Ultrasound in the diagnosis of cervical tuberculosis adenitis. Auris Nasus Larynx 25:67-72, 1998 8. Baatenburg de Jong RJ, Rongen RJ, Verwoerd CDA, et al: Ultrasound-guided fine-needle aspiration biopsy of neck nodes. Arch Otolaryngol Head Neck Surg 117402404, 1991 9. Bradus JB, Hybarger P, Gooding GAW: Parotid gland: US findings in Sjogren syndrome. Radiology 169:749751, 1988 10. Bruneton JN: Ultrasonography of the Neck. Berlin, Springer, 1987 11. Bruneton JN, Balu-Maestro C, Marcy PY, et al: Very high frequency (13 MHz) ultrasonographic examination of the normal neck. Detection of normal lymph nodes and thyroid nodules. J Ultrasound Med 13:8790, 1994 12. Bruneton JN, Normand F, Santini N, et al: Salivary glands. In Bruneton JN (ed): Ultrasonography of the Neck. Berlin, Springer, 1987, pp 64-80 13. Candiani F, Martinoli C: Salivary glands. In Solbiati L, Rizzatto G (eds): Ultrasound of Superficial Structures. Edinburgh, Churchill Livingstone, 1995, pp 125-139 14. Chang DB, Yang PC, Yu CJ, et al: Ultrasonography and ultrasonographically guided fine-needle aspiration biopsy of impalpable cervical lymph nodes in patients with non-small cell lung cancer. Cancer 5:1111-1114, 1992 15. Czembirek H, Friihwald F, Gritzmann N: Kopf-HalsSonographie. New York, Springer, 1988 16. Delorme S: Sonography of enlarged cervical lymph nodes. Imaging 60:267-272, 1993 17. Derchi LE, Serafini G, Rabbia C, et al: Carotid body tumors: US evaluation. Radiology 182:457-459, 1992 18. Dewes W, Gritzmann N, Koischwitz D, et al: High resolution small parts ultrasound (7,5 MHz) of the neck. Radiologe 36:12-21, 1996 19. Eichhom T, Schroder HG: Ultrasound in metastatic neck disease. ORL J Otorhinolaryngol Relat Spec 55:258-262, 1993 20. Eichhom T, Schroeder HG, Schwerk WB, et al: The importance of sonography in the follow-up of head and neck cancer. HNO 35:46?-467, 1987 21. El-Silimy 0, Comey C The value of sonography in the management of cystic neck lesions. J Laryngol Otol 107245251, 1993 22. Fruhwald F: Clinical examination, CT and US in tongue cancer staging. Eur J Radiol 8:236-241, 1988 23. Friihwald F, Neuhold A, Seidl G, et al: Sonography of the tongue and floor of mouth. Part 11. Neoplasms of the tongue. Eur J Radiol 6:108-112, 1986 24. Friihwald F, Salomonowitz E, Neuhold A, et al: Tongue cancer: Sonographic assessment of tumor stage. J Ultrasound Med 6:121-137, 1987 25. Gooding GAW: Malignant carotid artery invasion: Sonographic diagnosis. ORL J Otolarhinolaryngol Relat Spec 55:263-272, 1993 26. Gritzmann N: High resolution sonography of the salivary glands. AJR Am J Roentgenol 153:161-166, 1989
27. Gritzmann N: Sonographie bei cystoiden cervikalen Raumforderungen. Ultraschall Med 9:148-154, 1988 28. Gritzmann N: Sonography of the extra-thyroidal cervical soft tissue, the salivary glands and floor of the mouth. Eur J Ultrasound 1:9-21, 1994 29. Gritzmann N, Czembirek H, Hajek P, et al: The sonographic anatomy of the neck and its importance in the staging of lymph nodes in head and neck malignancy. Rofo Fortschr Geb Rontgenstr Neven Bildgeb Verfahr 146:l-7, 1987 30. Gritzmann N, Friihwald F: Sonographic anatomy of the tongue and floor of the mouth. Dysphagia 2 1 9 6 202, 1988 31. Gritzmann N, Grasl MC, Helmer M, et al: Invasion of the carotid artery and jugular vein by lymph node metastases. Detection with sonography. AJR Am J Roentgenol 154:411414, 1990 32. Gritzmann N, Herold C, Haller J, et al: Duplex-sonography of tumors of the carotid body. Cardiovasc Intervent Radiol 10:280-284, 1987 33. Gritzmann N, Koischwitz D: Ultrasound of the neck. J Otolaryngol 22:315320, 1993 34. Gritzmann N, Traxler M, Helmer M, et al: Sonography and CT in deep cervical lipomas and lipomatoses of the neck. Ultrasound Med 7451456, 1988 35. Koischwitz D: Sonographie der Kopf-Hals-Region. Berlin, Springer, 1993 36. Majer MC, Hess CF, Kolbel G, et al: Small arteries in peripheral lymph nodes: A specific US sign of lymphomatous involvement. Radiology 168:241-243, 1988 37. Mann WT, Beck A, Schreiber 1, et al: Ultrasonography for evaluation of the carotid artery in head a& ieik cancer. Laryngoscope 104:885888, 1994 38. Martinoli C, Derchi LE, Solbiati L, et al: Color Doppler sonography of salivatory glands. AJR Am J Roentgenol 163:933-941, 1994 39. Mori M, Sakamoto T, Takahashi M, et al: Facet formation sign in sarcoidosis: A new sign in endoscopic US. Radiology 169:113, 1988 40. Plas H, Peene P, Lemahieu SF, et al: Carotid artery aneurysm simulating a pyriform sinus mass. Rofo Fortschr Geb Rontgenstr Neven Bildgeb Verfahr 153:603-605, 1990 41. Rabinov K, Weber AL: Radiology of the Salivary Glands. Boston, GK Hall Medical, 1985 42. Rothstein SG, Persky MS, Horii S: Evaluation of malignant invasion of the carotid artery by CT scan and ultrasound. Laryngoscope 98321-324, 1988 43. Schroeder HG, Schwerk WB, Eichhom T: High resolution real time sonography in diseases of salivary glands. Part 11: Tumors. HNO 33:511-516, 1985 44. Schurawitzki H, Gritzmann N, Fezoulidis J, et a1 Ranking and indication of high resolution real-time sonography in non-tumourus diseases of the salivary glands. Rofo Fortschr Geb Rontgenstr Neven Bildgeb Verfahr 146:527-532, 1987 45. Schwerk WB, Schroeder HG, Eichhom T: High resolution real time sonography in diseases of salivary glands. Part I: Inflammatory conditions. HNO 33:505-510, 1985 46. Seifert G: Histopathology of malignant salivary gland tumors. Eur J Cancer 28:49-57, 1992 47. Solbiati L, Arsizio 8, Rizzatto G, et al: High-resolution sonography of cervical lymph nodes in head and neck cancer: Criteria for differention of reactive versus malignant nodes. Radiology 169:113, 1988 48. Solbiati L, Cioffi V, Ballarati E: Ultrasonography of the neck. Radiol Clin North Am 30:941-954, 1992
ULTRASOUND OF THE NECK 49. Solbiati L, Rizzatto G: Ultrasound of Superficial Structures. Edinburgh, Churchill Livingstone, 1995 50. Steiner E, Graninger W, Gritzmann N, et al: Colour coded duplex sonography of the parotid gland in Sjogren’s syndrome. Rofo Fortschr Geb Rontgenstr Neven Bildgeb Verfahr 160:294-298, 1994 51. Steinkamp HJ, Rausch M, Maurer J, et al: Colour coded duplex sonography for the differential diagnosis of cervical lymph node enlargement. Rofo Fortschr Geb Rontgenstr Neven Bildgeb Verfahr 161:226232, 1994 52. Takashima S, Sone S, Nomura N, et al: Non-palpable lymph nodes of the neck: Assessment with US and US-guided fine-needle aspiration biopsy. J Clin Ultrasound 25283-292, 1997 53. Takes RR, Knegt P, Manni JJ: Regional metastases in head and neck squamous cell carcinoma: Revised value of US with US-guided FNAB. Radiology 1981819-823, 1996 54. Teichgraber U, Steinkamp HJ, Mueffelmann M, et al: Differential diagnosis of lymph node lesions: A semiquantitative approach with power-Doppler sonography. Eur J Ultrasound lO(Supp1 1):16, 1999 55. Traxler M, Ertl U,Ulm C, et al: Sonographic diagnosis of the unilateral benign hypertrophic masseter muscle. 2 Stomatol 88:23-27, 1991 56. Tschammler A, Gunzer U, Reinhardt E, et al: Type diagnosis of enlarged lymph nodes by qualitative and semi quantitative evaluation of lymph node perfusion with colour coded duplex sonography. Rofo Fortschr Geb Rontgenstr Neven Bildgeb Verfahr 154:414-418, 1991 57. Tschammler A, Wirkner H, Ott G, et al: Vascular patterns in reactive and malignant lymphadenopathy. Eur Radiol 6:473-480, 1996 58. Van den Brekel MWM, Castelijns JA, Snow GB, et al: The size of lymph nodes in the neck on sonograms as a radiologic criterion for metastasis: How reliable is it? AJNR Am J Neuroradiol 19:2191-2197, 1997
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59. Van den Brekel MWM, Castelijns JA, Stel HV, et al: Occult metastatic neck disease: Detections with US and US-guided fine-needle aspiration cytology. Radiology 180:457-462, 1991 60. Van den Brekel MWM, Van den Waal I, Meyer CJLM, et al: The incidence of micrometastases in neck dissection specimes obtained from elective neck dissection. Laryngoscope 106:987-991, 1996 61. Vassallo P, Wernecke K, Roos N, et al: Differentiation of benign from malignant superficial lymphadenopathy: The role of high resolution US. Radiology 183:215-220, 1992 62. Wang AM, OLeary DH: Common carotid artery aneurysm: Ultrasonic diagnosis. J Clin Ultrasound 16:262-264, 1988 63. Weissman JL: Imaging of the salivary glands. Semin Ultrasound CT MR 16:546-568, 1995 64. Westhofen M. Ekasound B-scans in the fol\ow-uf of head and neck tumours. Head Neck Surg 9:272278, 1987 65. Wittich GR, Scheible WF, Hajek P: Ultrasonography of the salivary glands. Radiol Clin North Am 23:2937, 1985 66. Ying M, Ahuja AT, Evans R, et al: Cervical lymphadenopathy sonographic differentiation between tuberculous nodes and nodal metastases from non head and neck carcinoma. J Clin Ultrasound 26:383-389, 1998 67. Yousem DM, Som PM, Hackney DR, et al: Central nodal necrosis and extracapsular neoplastic spread in cervical lymph nodes: MR imaging versus CT. Radiology 182:753-795, 1992 68. Yusa H, Yoshida H, Ueno E: Ultrasonic criteria for diagnosis of cervical lymph node metastases of squamous cell carcinoma in the oral and maxillofacial region. J Oral Maxillofac Surg 57:41-48, 1999 69. Zanella FE, Beyer D, Cornelius G, et al: Real time sonography in the diagnosis of cysts in the neck. Rofo Fortschr Geb Rontgenstr Neven Bildgeb Verfahr 145:278-282, 1986
Address reprint requests to Dietmar Koischwitz Radiologisches Zentralinstitut Krankenhaus Siegburg GmbH Ringstrasse 49 D-53721 Siegburg Germany
0033-8389/00 $15.00
+ .OO
ULTRASOUND OF THE NECK Dietmar Koischwitz, MD, and Norbert Gritzmann, MD
High-resolution B-mode sonography has improved in the past few years and has become a very valuable tool in the diagnosis of diseases of the head and neck. Sonography is commonly the first imaging modality after clinical examination. It is easily tolerated by patients and is inexpensive. It provides valuable diagnostic information with a high degree of diagnostic accuracy. On the basis of the sonographic findings, selection of additional imaging modalities including CT and MR imaging can be applied more judiciously. This article provides the most up-to-date information about the indications, findings, and limitations of high-resolution B-mode sonography in the evaluation of head and neck pathology. INSTRUMENTATION Optimal ultrasound (US) examination of the superficial structures of the head and neck requires appropriate equipment with highresolution small-parts transducers that make use of high-frequency US. US sequences between 5 and 20 MHz are used (most commonly 7.5 to 10 MHz). Either the transducer is placed directly on the skin or a silicon stand-off pad is placed between the transducer and the skin to get ideal contact with the surface, especially in the angle of the jaw and the neck. High-frequency small-parts sonography, using frequences between 5 and 10
MHz, is used for the near field; this allows an axial resolution of 0.5 mm or less and a lateral resolution of 1 mm or less. The spatial resolution improves when high frequencies (15 to 20 MHz) are used, which provide nearly microscopic resolution of small areas.35 EXAMINATION TECHNIQUE A systematic examination protocol is mandatory for the evaluation of the head and neck. It begins with the examination of the thyroid gland where the instrument is adjusted and frequency and gain are optimized. The examination is continued along the vascular sheath to the floor of the mouth, tongue, and the salivary glands and tonsils. The next step is to examine the status of the lymph nodes including nuchal, accessory, and transverse cervical nodes. If clinically indicated, the larynx and cervical esophagus are also evaluated.18,35
CERVICAL LYMPH NODES The majority of the normal lymph nodes in the head and neck show an axial diameter of 2 to 5 mm with the exception of the jugulodigastric and the jugulo-omohyoid lymph nodes, which are larger and reveal an axial diameter of 8 to 10 mm, and a longitudinal diameter of 15 to 20 mrn.lo,15,35 Normal lymph
From the Central Department of Radiology, Siegburg Hospital GmbH, Siegburg, Germany (DK); and the Departments of Radiology and Nuclear Medicine, Hospital of the Brothers of St. John, Salzburg, Austria (NG)
RADIOLOGIC CLINICS OF NORTH AMERICA VOLUME 38 * NUMBER 5 SEPTEMBER 2000
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nodes are difficult to detect because of their high echogenicity, which is similar to that of the surrounding fatty tissue. They can only be demonstrated by the use of high frequencies (13 MHz)." Diseases of the lymph nodes lead to an increase of fluid either by swelling of the histiocytes in the sinus, by hyperplasia of lymph follicles, or by invasion of tumor cells. As a consequence, this results nearly always in enlargement of the lymph nodes and a reduction of the e~hogenicity.~~
REACTIVE LYMPH NODES
Enlarged reactive lymph nodes are the most frequent sonographically encountered entities in the head and neck in nonselected patients. Some reactive lymph nodes are found in nearly every patient, most commonly the submandibular and lateral cervical nodes. The reactive enlargement of the lymph nodes is the response to past inflammatory disease and is reflected bv histiocvtosis in the lymph node sinus. The typical sonographic appearance shows a longitudinal-to-oval shape with rounded poles and a smooth border. The echogenicity is low and homogeneous with a hyperechoic peripheral or central band, consisting of the lymph node hilus with fat and small vessels (Fig. 1).The axial diameter is usually less than 8 mm, whereas the longitudinal diameter can range from 15 to 20 mm.2
Figure 1. Reactive-hyperplastic lymph nodes, left lateral cervical. Hypoechoic structure with moderate enlargement, smooth border, and preserved eccentric hyperechoic hilus.
Figure 2. Acute nonspecific lymphadenitis, left submandibular. Craniocaudal section. Round spherical and ovalshaped hypoechoic lymph node with a smooth border and hilus not detectable.
INFLAMMATORY LYMPH NODE DISEASE
In acute, nonspecific lymphadenitis the lymph nodes are painful and markedly enlarged. Their shape is longitudinal or ovoid with rounded poles. In addition, they may be round to spherical with smooth borders and display a hypoechoic appearance. The hilus of the lymph node is not always apparent. The differentiation from the surrounding soft tissues and from other lymph nodes, however, is mostly discernible (Fig. 2). The enlargement of acute inflammatory lymph nodes ranges from 20 to 25 mm in longitudinal diameter; however, it should be emphasized that the absolute measurements of the size of a lymph node, such as the longest diameter, is not sufficient for differentiation of inflammatory from metastatic lymph nodes. Different authors'6,42 have shown that the ratio between longitudinal and transverse diameter of a lymph node (longitudinal-trunsverse diameter ratio), also known as the shortto-long-axes ratio, or the maximal-transverse quotient, also known as roundness index (RI), has a higher degree of accuracy in the differentiation between inflammatory and metastatic lymph nodes. A RI greater than 2 (longitudinal shape) indicates inflammatory disease in 84%, whereas a RI less than 1.5 (spherical shape) favors metastatic involvement in 71% of cases.47 In subacute inflammation the lymph nodes
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echogenic subcutaneous fatty tissue and muscles. PRIMARY LYMPH NODE DISEASES
Figure 3. Specific lymphadenitis (tuberculosis) in the upper third of the right lateral cervical group. Spherical shape with irregular border and with central necrosis of the involved lymph node. Adjacent to it are four smaller reactive lymph nodes.
tend to become smaller. This can be well documented by sonography. The shape remains longitudinal, the borders are smooth, and the internal architecture is less hypoechoic. The lymph node demonstrates small spots and stripes and the echogenic hilus is visible. In chronic inflammation, after weeks and months, when the clinical symptoms have subsided, the lymph nodes can still be detected by sonography. They are small, soft, movable, slightly hypoechoic with smooth borders, and have a longitudinal shape.
Sarcoidosis (Boeck's disease) is a benign granulomatous disease of the lymph nodes, whereas Hodgkin's and non-Hodgkin's lymphomas are aggressive malignant lymph node neoplasms. Both reveal sonographically similar and overlapping features. In nearly every case multiple lymph nodes are involved (e.g., one or two regional groups), which result in conglomeration of the enlarged lymph nodes. The individual nodes are round to oval in shape. A solitary involvement of only one lymph node is rare. On sonography these lymph nodes demonstrate a round-to-spherical shape, and occasionally very large lymph nodes reveal low echogenicity or appear nearly nonechoic, simulating a cyst. Sometimes there are tiny echogenic foci in the nonechoic structures of the lymph nodes (punctate echo structure). The borders are smooth and the differentiation between the involved lymph node and the surrounding tissues is clearly delineated (Fig. 4). In cases with rapid, aggressive growth of malignant lymphomas perinodal edema may occur. Extranodal spread with infiltration of surrounding tissues rarely occurs. In sarcoidosis the lateral cervical lymph nodes and transverse supraclavicular lymph nodes are frequently involved bilaterally, as well as, occasionally, the intraglandular pa-
SPECIFIC LYMPHADENITIS
Specific lymphadenitis is principally caused by tuberculosis. The involved lymph nodes are commonly large, painless, or slightly painful under pressure. There is a significant discrepancy between the individual involved lymph nodes, with a spectrum ranging from large, round, nonechoic, to cystic-necrotic nodes with blurred borders. The surrounding uninvolved lymph nodes appear 66 Edema in the reactive and hyperpla~tic.~, surrounding tissue adjoining the tuberculous lymph node mass imparts a blurred appearance to the borders of the lymph nodes (Fig. 3). Inflammation in the surrounding tissues with the formation of fistulas may ensue in cases with nodal necrosis, abscess formation, and perforation of the capsule of the lymph nodes. Fistulas appear as hypoechoic or nonechoic linear stripes and contrast with the
Figure 4. Malignant B-cell lymphoma. Manifestation in the right lateral chain. Hypoechoic structure, smooth border, no extranodal tumorous spread, with a deformity and flattening against each other. Facet formation sign.
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rotid lymph nodes. In Hodgkin’s disease or non-Hodgkin’s lymphoma the involved lymph nodes are located most commonly posterior to the sternocleidomastoid muscle, whereas metastases from squamous cell carcinoma are localized more frequently in front of the sternocleidomastoid muscle. When rapid growth of the lymph nodes occurs in the early stages of malignant lymphoma extranodal expansion may occur late leading to deformation and flattening of the lymph nodes against each other, referred to as the facet formation sign.39In B-mode sonography echogenic lines or double lines are demonstrated between the enlarged lymph nodes. They represent encased, but not infiltrated, small vessels (small-vessel sign).36This is analogous to the sandwich-sign of the mesenteric vessels in the upper abdomen. LYMPH NODE METASTASES
Cervical lymph node metastases in the head and neck region are caused by squamous cell carcinoma in 80% of cases. Characteristic sonographic findings of metastatic lymph node disease are enlargement with a round-to-spherical shape. Commonly they are hypoechogenic, occasionally inhomogeneously echogenic, with a loss of the hilar definition. In cases of extranodal spread with infiltrative growth, the borders are poorly defined.2,13. 16. 19. 29,47,48,53,58,61,67 Common findings of metastases from squamous carcinoma are extranodal spread and central necrosis together with liquid areas in the lymph nodes 68 Lymph node metastases from ma(Fig. 5).67, lignant melanoma and papillary thyroid carcinoma have a nonechoic, nearly echo-free appearance, mimicking a cystic lesion. The sonographic diagnosis of lymph node metastases from thyroid carcinoma is more difficult than the diagnosis of metastases from squamous cell carcinoma. In some metastatic thyroid carcinomas the tumor cells infiltrate and invade the lymph node only partially and peripherally with no increase in the nodal size. Metastases of medullary and papillary thyroid carcinomas may show small punctate calcifications, referred to as psammoma bodies. The metastases may have increased vascularity. By applying color-coded duplex sonography (CCDS) it is possible to demonstrate the pathologic increased vascularity even in small lymph node metastases of 3 to 4 mm in diameter. On B-mode sonog-
Figure 5. Lymph node metastasis from squamous cell carcinoma of hypopharynx-left cervical-lateral. lntranodal necrosis.
raphy these small metastatic nodes show a hypoechogenic cystic appearance. On CCDS the number of visible vessels is disproportionally high relative to the small nodal size. Sensitivity of US in the diagnosis of cervical lymph node metastases is approximately 89% to 95%,16,19whereas specificity is about 80% to 95%.19* 56, 61 The lower percentage of specificity by US is accounted for by the difficulties in differentiating between enlarged nodes of reactive lymphoid hyperplasia and enlarged metastatic nodes. The round-to-spherical shape of the nodes is the most important criterium in the diagnosis of metastatic lymph node disease, which is clearly expressed in the RI.47, 58 Nevertheless, the sonographic differentiation between benign and malignant lymph nodes can be very difficult because of the overlap in the echogenic features and the shape of the pathologic nodes. The relationship of large lymph node metastases and tumoral invasion of the large vessels can be optimally assessed by sonography. Infiltration of the carotid arteries occurs in less than 15% of cervical metastatic lymph nodes. A direct sign of tumorous infiltration of the vessel (to the level of the media) is the conversion of the normally echogenic wall of the carotid artery to a hypoechogenic wall, which is demonstrated in 90% of cases.25,31 The length of the circumferential contact with the tumor is diagnostically significant. The probability of invasion of the wall of the artery increases when tumor covers a length of over 3.5 cm and when the circumferential encasement is over 150 degrees (Fig. 6). In the last few years
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Figure 6. Large metastatic lymph node tumor from small cell carcinoma of bronchus. A, Transverse; 6,longitudinal section. The length of contact between tumor and the common carotid artery is 5 cm. In transverse section the common carotid artery is encased by more than 150". Hypoechoic transformation of the otherwise echogenic wall of the artery. A tumorous infiltration into the vessel wall must be assumed.
different authors have used CCDS or power Doppler sonography for differentiation of di54, 56 by classifying verse lymphaden~pathies~~, lymph node perfusion. This has remained up until now more subjective because of lack of 54, 56 reliable objective criteria.51, In reactive lymph nodes a central linear or central hilar increased perfusion is found. In acute lymphadenitis a subjective recognizable, sometimes massive increased perfusion is found and the vascular architecture is preserved (color Fig. 7A). A missing or weak perfusion correlates with chronic inflammation but also with metastases. In metastatic squamous cell carcinoma different patterns of perfusion are found including peripheral increased perfusion, focal absence of perfusion (color Fig. 7C), absence of central vessels, displacement of vessels, or a chaotic irregular pattern of perfusion (color Fig. 7B). Highresistance indices or a high variation of the resistance index in the involved lymph nodes is regarded as a sign of metastatic involvement.19,56 The technologic possibilities for measurement of resistance indices in small, borderline lymph nodes of 6 to 8 mm diameter, however, are limited. In malignant lymphomas increased perfusion is found with preservation of the architecture of the vessels, similar to the findings in acute inflammatory disease (Fig. 70).57The classification of lymph node perfusion is very subjective and not applicable as a single method for differentiation
of the various lymphadenopathies. Increased perfusion can be found in malignant lymphomas and in inflammation. On the other hand, a reduction of perfusion can occur in regressive alterations of lymph nodes and in metastatic involved lymph nodes. There has been no progress in the use of contrast medium in sonographic differentiation of lymphadenopathies. The arrangement of intranodal vessels and their diagnostic analysis are noncontributory even though they are better delineated. US-guided fine-needle aspiration biopsy is recommended for histologic differentiation of the various lymph node path~logies.~,l4 Today it is still the best and most accurate method for the diagnosis of lymph node metastases. Nonpalpable lymph nodes can be punctured under sonographic guidance.52 Sensitivity, specificity, and positive and negative predictive value are reported in the literature with percentages between 95% and 980/o. 53, 59, 60 .st
PRIMARY SOFT TISSUE TUMORS
Hemangiomas and Lymphangiomas These lesions occur most commonly during the first 2 years of life or even in utero. They are divided into capillary or cavernous and are multicystic, fluid-filled cavities. The echogenicity is variable and depends on the size
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Figure 7. Lymph node perfusion. A, Lymphadenitis. Oval-shaped lymph node in the parotid gland with hilar perfusion running out of the eccentric hilum. 6,Lymph node metastases of an epithelial carcinoma in the accessory group. Spherical hypoechoic lymph node with chaotic perfusion. C, Lymph node metastasis of a papillary carcinoma of the thyroid gland, cervical-lateral. Cystic area in the lymph node and a striking increased perfusion in a septum. Illustration continued on opposite page
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Figure 8. Cystic lyrnphangioma. Transverse submental section. Multiple cystic communicating spaces filled with hypoechoic fluid.
Figure 7 (Continued). 0,Non-Hodgkin's lymphoma. Threedimensional power angio mode showing increased wellarranged hilar vascularization.
of the cystic component. They can be hypoechoic or more or less isoechoic, but usually are hyperechoic compared with the surrounding cervical soft tissues. They are highly c~mpressible.'~ Cystic lymphangioma (hygroma) can be firm and elastic, so that palpation often suggests a lipoma; however, sonographically the nonechoic cystic appearance is diagnostic (Fig. 8). CCDS helps to detect the perfusion in hemangiomas and confirm the vascular nature of the lesion.
ease, and neurinomas after amputation or operation are commonly located in the dorsolateral parts of the neck behind the sternocleidomastoid muscle. They show a hypoechogenic pattern with a smooth capsule (Fig. 10). Sometimes degenerative cystic changes occur. In some cases it is possible to demonstrate the continuity of the neurinoma with the nerve, which shows a spindle-shaped thickening at the junction between the nerve and the tumor.
Lipomas Most lipomas have an ovoid shape; are located superficially in the subcutaneous tissues; and are soft, elastic, and compressible. Pure fat-containing lipomas are rare and are relatively h y p o e ~ h o g e n i c The . ~ ~ more common fibrolipomas have a high echogenicity with a typically striated, feathery appearance (Fig. 9). Neural Tumors Neurofibromas, s c h w a ~ o m a s ,Or multiple neurofibromas in von Recklinghausen's dis-
Figure 9. Lipofibroma, infraparotid left. Elliptical hypoechoic tumor with some echogenic stripes caused by fibers.
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KOISCHWITZ & GRITZMANN
mass at the carotid bifurcation with increased 32 va~cularity.'~, ABNORMALITIES OF THE CERVICAL VESSELS
Figure 10. Schwannoma. Craniocaudal section, left cervical-lateral. Medium hypoechoic structure of an ovalshaped tumor with smooth borders between sternocleidomastoid muscle and common carotid artery.
Aneurysms, elongation, and tortuosity of the carotid arteries can cause tumorlike swellings in the neck that can be mistaken for a tumor or a lymph node lesion.40, They usually manifest as a pulsatile neck mass. A partially thrombosed aneurysm of the carotid artery is rare but may simulate a tumor. Bmode sonography is capable of delineating an aneurysm or tortuous carotid arteries (Fig. 12). The additional use of CCDS clarifies the diagnosis and differentiates nonperfused material in an aneurysm from perfusion of a tumor.
TUMORS OF THE CAROTID BODY (CHEMODECTOMAS)
CYSTIC LESIONS
Carotid body tumors are typically localized within the carotid bifurcation or adjacent to the carotid arteries with displacement of the internal and external carotid arteries. These tumors are highly vascular, which can usually be demonstrated by B-mode sonography (Fig. 11).CCDS displays the mass and its vascularization. The diagnosis of a carotid body tumor is based on the sonographic findings of a
Cystic lesions in the head and neck are not uncommon. The frequency of cysts in the head and neck is in the range of 1%to According to publications in the literature there are more than 20 different cystic entities.21,27* 69 The most common cysts originate from the thyroid gland, the thyroglossal duct, and branchial clefts, followed by cystic lymphangiomas. The remaining cystic lesions include ranula, dysodontogenetic cysts, lar-
Figure 11. Chemodectoma in the left carotid bifurcation. A, Transverse section. Solid inhomogeneous tumor with substantial vascularization. 6,Craniocaudal section. Encasement of the carotid bifurcation with spread of the vessels. ACI = internal carotid artery, ACE = external carotid artery, ACC = common carotid artery.
ULTRASOUND OF THE NECK
Figure 12. Fusiform aneurysm of the common carotid artery with partial thrombosis. Arrows mark the outline of the aneurysm.
yngoceles, and so forth. In patients with metastatic squamous cell carcinoma of the neck necrotic lymph node metastases may mimic a cyst.
1037
variable echogenicity. They can be echo-free, but most of the cysts are moderately echogenic and homogeneous, revealing a very fine granular echo pattern caused by cellular debris or crystals of cholesterol within the cyst fluid.4,27 The echo pattern usually is more heterogeneous and echogenic when concomitant inflammation exists (Fig. 14A). Reactive hyperplastic lymph nodes can be found in the adjoining soft tissue structures. In some cysts there is an interface between the echo-free fluid and the echogenic material (composed of cellular debris and crystals) in dependent positions. The sediment material can be mobilized by exerting intermittent pressure with the fingertips on the cyst wall, differentiating debris from solid tissue in the cyst wall. Power sonography differentiation of inflammation of cysts from inflammation of adjacent lymph nodes by the lack of perfusion in cysts. In the rare cases with development of a carcinoma in a branchial cleft cyst B-mode sonography can demonstrate the solid tumor component in the cyst (Fig. 14B) and Doppler sonography can confirm tumor vascularization.
Thyroglossal Duct Cysts
Thyroglossal ducts cysts are located in or near the midline of the neck, between the f m m cecum ~ ~ of the tongue base and the pyramidal lobe of the thyroid gland. They are most commonly located at the hyoid bone and in most cases there is a connection between the cyst and the hyoid bone.', On sonograms the thyroglossal duct cyst appears as a typical cystic lesion, nonechoic or hypoechoic with posterior acoustic enhancement and well-defined margins. Occasionally they are multicystic and contain solid components of echogenic thyroid tissue (Fig. 13).In case of infection the cyst becomes painful and the fluid in the cyst displays inhomogeneous echoes from pus. In 1%of thyroglossal duct cysts a carcinoma may develop, usually a papillary adenocarcinoma. In such cases the cyst increases in size and solid tumor tissue fills out the cystic lumen.
Epidermoids and Derrnoids (Dysodontogenic Cysts)
Epidermoids or dermoids are mainly localized in the midline of the tongue and the floor of the mouth. They are caused by epidermoid cell inclusions during the process of fusion of the branchial arches. These cysts are
Branchial Cleft Cysts
Branchial cleft cysts are located most comregi0nTventrolatmonly in the lateral era1 to the carotid bifurcation. They develop from the first or second branchial clefts with
Figure 13. Thyroglossal duct cyst. Craniocaudal section. C = cyst with solid components and with close relation to the hyoid bone (OH).
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KOISCHWITZ & GRITZMANN
Figure 14. Branchial cleft cyst. A, Craniocaudal section. Inflammation of the cyst. Moderate hypoechoic fluid is present with concomitant lymphadenitis (LK). 6,Craniocaudal section. Carcinoma in a branchial cleft cyst. Mostly solid tissue in the cyst.
often highly echogenic because of the increased acoustic impedance of fluid, sebum, or hairs in the lumen (Fig. 15). The change in shape of these echogenic cysts during speaking, swallowing, and tongue movement can be demonstrated sonographically and thereby exclude a solid tumor. Ranula Ranula is a cyst in the floor of the mouth of variable size and shape, caused by obstruction of sublingual ducts. Occasionally they
can become large and lead to deformity of the floor of the mouth. They can plunge caudolaterally over the posterior margin of the mylohyoid muscle or bulge in a dorsal direction with consequent difficulties in speaking and swallowing. In the case of an intraglossal location clinical differentiation from a tumor may be difficult. Sonography demonstrates a cystic, nonechoic or hypoechoic lesion, or occasionally a more echogenic lesion secondary to intracystic cellular debris. The margins are smooth and sometimes septations are found. During chewing, eating, and swallowing the cyst changes its shape and tends to bulge caudolaterally. Laryngoceles Laryngoceles are dilatations of the samle of the laryngeal ventricle of Morgagni. They can contain mucous, saliva, or air. They are classified as internal, external, and combined dependent on their location relative to the larynx. Most common symptoms are hoarseness, stridor, dysphagia, and swelling in the neck. If calcification of the thyroid cartilage does not interfere US may visualize a fluid-filled laryngocele as an echo-free, welldefined structure inside the thyroid cartilage (internal laryngoceles) and at the level of the thyrohyoid membrane (combined type) (Fig. 16).5 SALIVARY GLANDS
Figure 15. Epidermoid cyst in the tongue. Transverse section. Epidemic cyst with internal horn dandruffs. M MH = mylohyoid muscle.
The parotid, the submandibular, and the sublingual glands can be visualized sono-
ULTRASOUND OF THE NECK
1039
Sjogren’s Syndrome
In advanced cases of autoimmune sialadenitis sonography visualizes multiple cystic lesions caused by parenchymal destruction along with dilatation of the intraglandular ducts.9The remaining parenchyma is inhomogeneous and hypoechoic. With color Doppler sonography hypervascularization of the gland parenchyma can be demonstrated in 50% of patients (parotid inferno).50The increased vascularization of the involved gland correlates with the severity of the parenchymal changes. Sarcoidosis of the Parotid Glands Figure 16. Laryngocele. Transverse section of the larynx. A cystic saccule is found in the larynx and in the extralaryngeal right paralaryngeal space (combined type). C = laryngocele, L = larynx.
graphically. The glands are typically homogeneous echogenic structures. The intraglandular and extraglandular ducts can only be visualized sonographically by use of highfrequency, high-resolution transducers (11 MHz and higher). The facial nerve in the parotid gland most often cannot be visualized. Inflammatory disease is the most common abnormality of the salivary glands. The ratio of the different diseases of the salivary glands are estimated as sia1adenitis:sialolithiasis:sialadenosis:sialoma 100:50:10:1.15,26
The extrapulmonary manifestations of sarcoidosis affect the parotid glands in 1%to 6% and may be associated with uveitis and facial paralysis (Heerfordt’s s y n d r ~ m e )Sonogra.~~ phy demonstrates well-defined, painless enlargement of the parotid glands with a few or multiple small hypoechogenic granulomatous nodules, which are diffusely distributed throughout the glands. Sialolithiasis
Salivary stones cause painful, intermittent swelling and pain during eating. The submandibular gland is the most common site of
Acute and Chronic Sialadenitis
Acute bacterial sialadenitis occurs predominantly in elderly and debilitated patients. The salivary glands can also be involved in viral infections, including epidemic parotitis. Specific infections, such as tuberculosis or actinomycosis, are infrequent. In about 50% of cases with stones there is associated sialadenitis. In acute or chronic sialadenitis sonography demonstrates inhomogeneous hypoechogenicity of the glandular parenchyma. In acute inflammation hypoechogenicity is often more dominant than in chronic inflammation (Fig. 17). Sonographic findings occur in 18% of patients with chronic recurrent inflammation. These consist of inhomogeneous, patchy changes with duct ectasia in the parenchyma.12,28,44
Figure 17. Acute sialadenitis in the left parotid gland. Transverse section showing unilateral enlargement of the gland. lnhomogeneous hypoechoic parenchyma. Liquid-containing abscess with abscess membrane (arrows). UK = jaw.
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KOISCHWITZ & GRITZMANN
involvement (83%), followed by the parotid gland (13%) and, rarely, the sublingual gland S YO).^', Eighty percent of the stones are calcified and can be detected by conventional radiograph examination. Sonography has the capability to localize nonopaque stones that cannot be visualized by plain film examination. Stones are located in the glands or in the ducts. Concomitant inflammation with dilatation of the ducts occurs (Fig. 18A). The accuracy of sonography in salivary lithiasis ranges from 80% to 94%.41,45, 65 The typical sonographic appearance of a salivary stone reveals an echogenic complex with sound shadowing (Fig. 18B). Stones smaller than 2 mm in diameter may not show a shadowing. Errors in diagnosis occur in very small stones in the intraglandular ducts without ductal dilatation. Demonstration of small stones is facilitated by increasing salivary flow with the administration of a lemon stick, which leads to duct ectasia, and stones are recognized more clearly. Sialadenosis Sialadenosis is a noninflammatory, nonneoplastic, symptomatic enlargement of the salivary glands, most commonly involving the parotid glands. It is commonly associated with endocrine diseases; nutritional or metabolic states; and following administration of certain drugs (anorexia, diabetes, alcoholism, and so forth). The sonographic examination shows enlarged glands, with homogeneous,
echogenic parenchyma excluding enlargement of the glands secondary to tumor or adjoining lymph node enlargement.43,a
TUMORS OF THE SALIVARY GLANDS Salivary gland tumors constitute about 0.3% of all neoplasms. They are located in the parotid glands in 70% to 80% of cases. Pleomorphic adenomas comprise 70% to 80% of parotid tumors, whereas 5% to 10% are papillary cystadenoma lymphomatosum (Wharthin’s tumor). Tumors of the parotid glands are malignant in about 10% of cases, of the submandibular gland, in about 45%, and of the sublingual glands in about 90% of cases.46,65 Benign Tumors of the Salivary Glands Pleomorphic Adenoma
Pleomorphic adenoma is the most frequent tumor of the salivary glands (24%to 71%).43,46 The adenoma is localized in the superficial lobe of the gland in 90% and the deep lobe in about 10% of cases. The tumor is composed histologically of epithelial, myoepithelial, and mesenchymal tissues. Because of its mixed and variable composition, the sonographic appearance is also varied. The tumor is well circumscribed and reveals a homogeneous ul-
Figure 18. Sialolithiasis. A, Right submandibular gland. Hypoechoic enlargement of the gland, and ductectasias of the intraglandular ducts. lntraductal concrement with echogenic surface and dorsal shadowing (SS). B, Submandibular duct (D SM). lnhomogeneous hypoechoic structure of the submandibular gland (GL SM). Encased stone with echogenic surface and dorsal shadowing (arrows).
ULTRASOUND OF THE NECK
1041
trasonic pattern with decreased echogenicity and a smooth or polycyclic border (Fig. 19). Occasionally, the tumor is hyperechoic and cystic areas or calcifications may be seen. Malignant transformation of a pleomorphic adenoma occurs in 1.5%to 4.5%, which is characterized by an irregular border and an inhomogeneous, hypoechoic, or nonechoic imaging pattern. Cystadenolymphoma
Cystadenolymphoma (Wharthin’s tumor) is the most frequent monomorphic adenoma of the salivary glands. It is composed histologically of epithelial and lymphoid components. The tumor represents 2% to 24% of all tumors of the salivary glands. In 90% Warthin’s tumors are located in the superficial lobe of the parotid gland, and in 8% to 30% they occur bilaterally. Sonographically, the Wharthin’s tumor has a smooth border, is hypoechogenic, and homogeneous or inhomogeneous with cystic areas with multiple septae (Fig. ZO).43 Larger cysts appear nonechoic with posterior acoustic enhancement. Malignant Tumors of the Salivary Glands
The most frequent malignant tumors in the salivary glands are mucoepidermoid carcinoma followed by adenoid cystic carcinoma, squamous cell carcinoma, acinic cell tumor, and adenocar~inoma.~~ The histologic differ-
Figure 20. Cystadenolymphoma (Wharthin’s tumor) in the right parotid gland. Hypoechoic inhomogeneous, in part cystic tumor in the dorsal-caudal area of the gland.
entiation according to their aggressiveness results in two main groups: (1) tumors with high-grade malignancy and (2) tumors with low-grade malignancy. A histologic diagnosis cannot be established sonographically as with other imaging methods. Malignant tumors of small size (less than 2 cm) and tumors of lowgrade malignancy usually have a homogeneous sonographic pattern and smooth borders and are assessed incorrectly as benign. Tumors of high-grade malignancy and larger than 2 cm in diameter show mostly irregular borders and an internal heterogeneous echo pattern with irregular, fluid-filled necrotic areas. They present as an infiltrating mass and occasionally ipsilateral lymph node metastases (Fig. 21).63If the tumor is very large, sonography is not able to assess the infiltration into the deep surrounding structures, including the base of skull and mandible. In such cases CT or MR imaging is indispensable. Color Doppler sonography may demonstrate hypervascularity in carcinomas of the salivary glands and reveal multiple irregular vessels within the tumor. In malignant tumors there is increased vascularity along with a high arterial flow velocity.38A clear differentiation between benign or malignant tumor by means of morphologic criteria or evaluation of the perfusion is not possible in many cases. Nonepithelial Tumors of the Salivary Glands
Figure 19. Pleomorphic adenoma of the right parotid
gland. Oval-shaped, smooth, somewhat polycyclic border, hypoechoic inhomogeneous structure.
The benign tumors of the stroma of the salivary glands, such as angioma, lipoma,
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KOISCHWITZ & GRITZMANN
be misinterpreted as a tumor of the salivary glands.55The differentiation is easily made by US. A functional assessment is performed with measurement of the masseter muscle in a relaxed position and a strained position while biting.
INFECTION OF THE NECK, TONSILS, TONGUE, AND FLOOR OF THE MOUTH
Figure 21. Carcinoma of right parotid gland (mucoepidermoid carcinoma, high-grade type malignancy). Hypoechoic, very inhomogeneous tumor (TU) with irregular borders. Complete delineation is not possible.
neurinoma, and so forth, show a similar appearance as in other locations. The malignant nonepithelial tumors of the salivary glands including fibrous histiocytoma, malignant schwannoma, fibrosarcoma, and rhabdomyosarcoma reveal a hypoechoic pattern with irregular borders and infiltration of skin or bones. INTRAGLANDULAR METASTASES
Lymph node metastases of the parotid gland can occur, most commonly from malignant melanoma and squamous cell carcinoma of the skin and metastatic carcinoma of the breast and lung. Malignant lymphomas can involve the intraglandular parotid lymph nodes.
Inflammations in the area of the neck, tongue, and floor of mouth are not uncommon and can be caused by dental infection, tonsillitis, pharyngitis, and occasionally by foreign body perforation. US is useful for the evaluation of the extent and location of the inflammatory process and the search for an abscess cavity that necessitates surgical intervention. In phlegmon there is diffuse inflammatory edema in the neck and fascia1 spaces surrounding muscles and the great vessels. Sonographically an edematous, inflammatory, stripy collection of fluid between preformed anatomic structures is seen. Sometimes the source of the infection can be demonstrated. An abscess presents as a very painful circumscribed hypoechogenic or nonechoic, space-occupying lesion (Fig. 22). The central area of an abscess contains fluid, like pus, and can be echo free. The borders are irregular and blurred. Soft tissue remnants, vessels, or foreign bodies within the abscess cavity demonstrate echogenic reflections.
SWELLING OF SOFT TISSUES (PSEUDOTUMORS)
There is nonglandular circumscribed or diffuse swelling of the soft tissues in the neck including edema, lipomatosis, hematoma, and low-grade infection, which may mimic a tumor. They can be differentiated from a neoplasm or enlarged lymph nodes by sonography in conjunction with palpation. HYPERTROPHYOFMASSETER MUSCLES
Hypertrophy of the rnasseter I'nuscle can occur on one or both sides. Clinically, it may
Figure 22. Abscess in the base of tongue. Transverse section. Nearly nonechoic, liquid space-occupying lesion with irregular borders in the genioglossal muscle.
ULTRASOUND OF THE NECK
Aerobic bacteria may produce small bubbles of air seen as bright reflexes. TUMORS OF THE TONGUE AND FLOOR OF THE MOUTH
Benign tumors in the oral cavity are mostly papillomas of the tongue; goiter of the base of the tongue, and some mesenchymal tumors including fibroma, lipoma, or neurinoma. The most common benign tumor of the tongue in babies is hemangioma, which is most commonly congenital and causes macroglossia with a tendency to bleed. These hemangiomas can be diagnosed sonographically. They usually shrink in the course of years, which can be documented by US. This eliminates the need for MR imaging examination under anesthesia. The US pattern consists of hyperechoic areas interspersed with canalicular liquid spaces. Malignant tumors in the oropharynx represent about 5% of all malignancies. The most frequent tumor is carcinoma of the tongue. These carcinomas infiltrate the deep structures in the tongue and the oral cavity and commonly reveal ulcerations. At the time of diagnosis they are advanced and conform to stages T2 to T4 (Fig. 23).28Sonographically, cancer of the tongue presents as a hypoechogenic, inhomogeneous, space-occupying lesion with blurred borders within the echogenic intrinsic tongue muscles. Sonography can evaluate extension across the midline and infiltration of the floor of the mouth including mylohyoid muscle invasion and the relation-
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ship of the tumor to the mandible. T4 tumors often cannot be completely delineated, in particular the retropharyngeal extension and the parapharyngeal infiltration below the skull base.22-24,30
SUMMARY
Sonography, when performed by an experienced examiner, can be used for evaluation of many pathologies in the head and neck area. Some benign neck lesions, such as cysts, lipomas, carotid body tumors, and hyperplastic lymph nodes, have typical sonomorphology. Sonography has an accuracy rate of about 90% in cervical lymph node staging and can delineate subclinical lymph node recurrences. It is the method of choice for evaluation of tumor infiltrations of the wall of the great vessels. Salivary gland tumors in the superficial lobe can be delineated completely by sonography. Salivary stones can be detected and localized. Carcinoma of the tongue and floor of the mouth with T1 and T2 staging can be assessed by US. The use and contribution of color Doppler sonography for the assessment of pathologic entities in the neck is a method under clinical investigation. US-guided fineneedle aspiration biopsy of lymph nodes and tumors of the salivary glands is easy to perform and is characterized by high sensitivity and specificity. To perform US examinations of the head and neck area of the highest quality the examiner should be familiar with the anatomy of the head and neck, be informed about the clinical problem, and have experience in the interpretation of abnormal US findings. US of the head and neck area is one of the most difficult sonographic examinations and should be performed by an experienced physician.
References
Figure 23. Stage T4 carcinoma of the tongue, transverse section. Hypoechoic, in-depth infiltrating tumor (TU) with irregular borders, crossing the midline. Zunge = tongue.
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