DOI: 10.1148/rg.254045142
RadioGraphics 2005;25:931-948
© RSNA, 2005
Multimodality Imaging Evaluation of the Pediatric Neck: Techniques and Spectrum of Findings1
Jean-Yves Meuwly, MD,
Domenico Lepori, MD,
Nicolas Theumann, MD,
Pierre Schnyder, MD,
Ghazal Etechami, MD,
Judith Hohlfeld, MD and
François Gudinchet, MD
1 From the Departments of Diagnostic and Interventional Radiology (J.Y.M., D.L., N.T., P.S., G.E., F.G.) and Pediatric Surgery (J.H.), University Hospital, Rue du Bugnon 46, Lausanne, Switzerland. Presented as an education exhibit at the 2003 RSNA Annual Meeting. Received July 8, 2004; revision requested August 19 and received September 15; accepted September 17. All authors have no financial relationships to disclose.
Address correspondence to J.Y.M. (e-mail: Jean-Yves.Meuwly{at}chuv.ch).
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Abstract
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Neck masses are a common finding in children and can present a difficult diagnostic challenge. These masses may represent a variety of conditions having a congenital, acquired inflammatory, neoplastic, or vascular origin. The fascial spaces and compartments of the neck provide an approach to differential diagnosis, and extensive knowledge of the anatomy and contents of each cervical compartment is mandatory in the diagnosis of pediatric neck lesions. Several imaging techniques, including radiography, gray-scale and Doppler ultrasonography, conventional and three-dimensional computed tomography, magnetic resonance (MR) imaging, and MR angiography, have been proposed for the evaluation of such lesions, and each has its own advantages and limitations. The imaging findings in 120 children who had been referred or treated for cervical lesions were retrospectively reviewed, and a systematic multimodality imaging approach to pediatric neck lesions based on the involvement of anatomic compartments of the cervical region was developed to increase diagnostic efficiency. Careful attention to clinical history and physical examination findings, along with knowledge of the embryologic features and anatomy of the cervical region and a multimodality imaging approach, is very helpful in the diagnosis and management of pediatric neck lesions.
© RSNA, 2005
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LEARNING OBJECTIVES FOR TEST 2
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After reading this article and taking the test, the reader will be able to:
- Discuss a wide variety of congenital and acquired conditions of the pediatric neck.
- Identify the common locations and typical imaging appearances of various conditions by using the neck spaces as a basis for differential diagnosis.
- Describe the US, MR imaging, and CT features of pediatric neck lesions.
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Introduction
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Neck masses are frequently encountered in the pediatric population. Diverse conditions of congenital, acquired inflammatory, neoplastic, or vascular origin manifest as neck masses in children of various ages. These lesions vary in prevalence from common to very rare, and their absolute number remains unknown (1,2). Evaluation of neck masses in pediatric patients involves careful consideration of clinical history and accurate physical evaluation. The patient’s age provides important diagnostic information in cases of congenital lesions. Extensive knowledge of the embryologic features and anatomy of the cervical region and of the contents of each cervical compartment is helpful in narrowing the differential diagnosis of pediatric neck lesions. The fascial spaces or compartments are regions of loose connective tissue that fill the areas between the fascial layers. Some of these regions are virtual, whereas others contain major anatomic structures (3–5). These spaces and their contents provide an approach to differential diagnosis. Imaging is helpful in making an accurate diagnosis by means of a well-defined differential diagnosis. It also helps determine the nature and extent of a variety of neck lesions and helps assess the involvement of adjacent structures.
In this article, we provide an overview of the embryologic development and normal anatomy of the neck. In addition, we retrospectively review the conventional radiographic, gray-scale and Doppler ultrasonographic (US), conventional and three-dimensional computed tomographic (CT), and magnetic resonance (MR) imaging or MR angiographic findings in 120 children and compare these findings with surgical findings. In light of our findings, we propose a systematic multimodality imaging approach to pediatric neck lesions that is based on the involvement of anatomic compartments of the cervical region. These compartments include the superficial fasciae; the visceral compartment (retropharyngeal space, retrovisceral space, pretracheal space); and the danger, prevertebral, carotid sheath, parotid gland, submandibular, masticator, pretonsillar, parapharyngeal, posterior cervical, paravertebral, perivertebral, and sternocleidomastoid muscle spaces.
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Embryologic Development within the Neck
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In the head and neck, the paraxial mesoderm that forms at the end of the 1st month of gestation develops into the somitomeres and the somites, which will in turn develop into the branchial apparatus between the 4th and 7th weeks of gestation.
The branchial apparatus consists of the branchial arches, pharyngeal pouches, branchial grooves, and branchial membranes. Congenital malformations may appear during development of the branchial apparatus (first identified in the 4th week of gestation) into adult structures (Figs 1, 2). Branchial cleft anomalies may be classified as first, second, third, or fourth arch anomalies according to the pouch or cleft of origin. They represent a spectrum of developmental anomalies that include fistulas, sinuses, and cysts (1,3). First branchial cleft anomalies are composed of cysts (68% of cases), sinuses (16%), and fistulas (16%). The anatomic location of first arch anomalies is less predictable than those of the second, third, and fourth arches due to the complicated embryologic features of first arch anomalies. These lesions represent either cysts and sinuses of the preauricular region with a distal portion located anterior or posterior to the pinna, or lesions situated posterior or inferior to the angle of the mandible, lying near the branches of the facial nerve within the parotid gland. Second, third, and fourth branchial anomalies represent a spectrum of manifestations ranging from a fistula to an isolated cyst. Over 90% of branchial anomalies arise from the second branchial apparatus, with a predominance of cysts. Skin openings may be seen in cases of sinuses or fistulas. Four types of second arch cleft cysts have been described according to their location and course relative to the great vessels and pharyngeal wall (1). Third branchial arch cysts and fistulas have a cutaneous opening along the anterior border of the sternocleidomastoid muscle and pass anterior to the vagus nerve and above the hypoglossal nerve, but below the glossopharyngeal nerve. The tract crosses the thyrohyoid membrane and enters the piriform sinus. The fourth branchial apparatus contributes to the development of the larynx, which derives from the laryngotracheal groove formed during the 4th week of gestation. The laryngeal cartilages develop from the branchial arches, with the more cranial cartilages arising from the fourth arch and the caudal cartilages from the sixth arch (1,3,6).
The thymus develops from the endoderm of the third pair of pharyngeal pouches. Anomalies may result from incomplete descent of the thymus anlage into the chest. Retained thymic tissue may communicate with the pharynx through the thyrohyoid membrane. However, thymic tissue may be seen anterior or deep to the sternocleidomastoid muscle. Aberrantly located thymic cysts may result from cystic degeneration of epithelial remnants or from persistent parts of the thyropharyngeal duct.
The thyroid gland originates in the 3rd week of fetal life from a median endodermal thickening in the floor of the primitive pharynx (Fig 1). The thyroid primordium develops at the level of the foramen cecum, between the anterior two-thirds and the posterior one-third of the tongue. The developing gland passes anterior to the hyoid bone and laryngeal cartilages and descends in the neck anterior to the thyrohyoid membrane and the strap muscles, where it reaches its final position by the 7th week of gestation. The anlage of the gland is connected to the tongue by the thyroglossal duct during its migration. Cysts may form anywhere along the course followed by the thyroid gland (Fig 3) (6). The parathyroid glands arise from the third and fourth branchial pouches; most individuals have four parathyroid glands. The variability of the number and location of the parathyroid glands—particularly of the lower glands—is a cause of problems in the surgical exploration of the neck.
The lymphatic system begins to develop at the end of the 5th week of gestation, and the early lymph capillaries join to form a network of lymphatic vessels and lymph sacs. When portions of the jugular lymph sacs are pinched off, or when lymphatic spaces fail to connect with the main lymphatic channels, hygromas may occur (6).
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Normal Anatomy of the Neck
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The fasciae of the neck are well-defined sheets of fat and fibrous tissue that circumscribe several compartments or spaces. They are classically divided into superficial and deep cervical fasciae, the latter being subdivided into superficial, middle, and deep layers. The fascial spaces are regions of loose connective tissue that fill the areas between the fascial layers (Figs 4, 5). Some of these spaces are virtual, whereas others contain major anatomic structures of the neck (3–5). There is a lack of agreement among authors concerning the nomenclature of the spaces and their anatomic or functional intercommunication. In this article, we follow the most commonly used classification system. However, the spaces of the neck and their contents may provide a common nomenclature, a systematic anatomic and functional classification scheme, and an approach to differential diagnosis (Table). Although many diseases of the neck are not space specific, we discuss and illustrate examples of diseases related to specific spaces.
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Figure 4. Diagram illustrates the relationships of the prevertebral (1), danger (2), and parapharyngeal and carotid sheath (3) spaces to the visceral compartment (4) and the submandibular space (5).
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Figure 5a. Drawings of axial sections through the level of C4 (a) and C7 (b) demonstrate the spaces in the upper and midcervical visceral compartment, respectively. IJV = internal jugular vein, PCM = pharyngeal constrictor muscle, PSM = paraspinal muscle, SCM = sternocleidomastoid muscle, T = trachea, TG = thyroid gland, TM = trapezius muscle.
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Figure 5b. Drawings of axial sections through the level of C4 (a) and C7 (b) demonstrate the spaces in the upper and midcervical visceral compartment, respectively. IJV = internal jugular vein, PCM = pharyngeal constrictor muscle, PSM = paraspinal muscle, SCM = sternocleidomastoid muscle, T = trachea, TG = thyroid gland, TM = trapezius muscle.
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Radiologic Evaluation
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The radiologic evaluation of pediatric patients following physical examination usually begins with conventional and color Doppler US due to its nonionizing and noninvasive ability to depict superficial structures, often at bedside. US helps define the size and extent of localized superficial masses and helps confirm their cystic or solid nature. Color Doppler US may also demonstrate the vascularization of the mass or displaced normal surrounding vessels. US findings may not allow definitive characterization, especially in deeply situated spaces. CT aids in the morphologic characterization and staging of neck masses and allows precise visualization of fine bone structures, calcifications, and deep soft-tissue compartments that cannot be demonstrated with US. In children, particular attention should be paid to protecting the patient from radiation, and low-dose neck CT is mandatory to avoid unnecessary irradiation of the thyroid gland (7,8). MR imaging, with its multiplanar capability and absence of ionizing radiation, offers superior contrast resolution in evaluating masses in complex areas in children but usually requires sedation in patients under 6 years of age. Gadolinium-based contrast material may also improve the characterization of lesions (1,9,10).
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Pediatric Neck Lesions
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Superficial Fasciae
Teratomas are common congenital neoplasms consisting of tissues of all three germ cell layers. A prevalence of one in every 20,000–40,000 live births has been reported, with 5% of teratomas in newborns situated in the lateral and anterior cervical region (Fig 6) (1,2). The spectrum of teratomas includes dermoid cysts, which may occur in the orbit, nasal region, and oral cavity (floor of the mouth); epidermoid cysts; and teratoid cysts. All three types of cysts are covered by squamous epithelium. Skin appendages are present in the wall of the dermoid cyst. Teratoid cysts may contain other tissues (eg, from the nervous, gastrointestinal, or respiratory system). Fetal cervical teratomas are considered benign, but malignant transformation may occur (2,11,12). US features include solid and cystic structures within a heterogeneous mass, and calcifications are seen more frequently than cartilage and bone formation. CT may show a hypoattenuating, thin-walled unilocular mass, with frequent nodules in dermoid cysts and heterogeneous contents in teratomas due to various germinal components. At MR imaging, teratomas are hypo- to isointense on T1-weighted images and hyperintense on T2-weighted images. Dermoid cysts may be hyperintense on T1-weighted images because of lipid-containing areas, and coronal imaging is useful in depicting the anatomic relationships of these lesions to the mylohyoid muscle (1,2,11).
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Figure 6a. Mature neck teratoma in a 9-month-old boy. (a) Axial proton-density–weighted MR image shows a hyperintense subcutaneous mass in the right side of the neck (arrow). (b) Coronal T2-weighted MR image shows multiple cysts with heterogeneous signal intensity (arrowheads).
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Figure 6b. Mature neck teratoma in a 9-month-old boy. (a) Axial proton-density–weighted MR image shows a hyperintense subcutaneous mass in the right side of the neck (arrow). (b) Coronal T2-weighted MR image shows multiple cysts with heterogeneous signal intensity (arrowheads).
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Visceral Compartment
Most authors refer to the region that contains the pharynx, cervical esophagus, trachea, thyroid and parathyroid glands, larynx, recurrent nerves, and portions of the sympathetic trunk as the visceral compartment, although the terminology may be controversial. The visceral compartment contains the retropharyngeal space, the retrovisceral space, and the pretracheal space (3,4).
Retropharyngeal Space.—
Retropharyngeal space infection occurs in 96% of cases involving children under 6 years of age. Children with retropharyngeal cellulitis, adenitis, or abscess typically have a history of upper respiratory tract infection followed by high fever, dysphagia, neck pain, and stiffness. Retropharyngeal and parapharyngeal infections result from suppurative lymphadenitis associated with tonsillitis, sinonasal and dental infections, and otitis media. Rarely, retropharyngeal abscess is caused by pharyngeal or esophageal perforation. The retropharyngeal space is the second most common location of abscess after the peritonsillar space. The most frequently encountered bacteria are Streptococcus pyogenes, Staphylococcus aureus, and Bacteroides melaninogenicus (2,3). US may demonstrate hypoechogenic areas (Fig 7a) and adenopathy in symptomatic small children, but contrast material–enhanced CT is usually required to show enhancing lymphoid tissue and abscess formation marked by low central attenuation and ring enhancement (Fig 7b). A complete circumferential rim of enhancement is the hallmark of abscess, whereas partial or no enhancement indicates a phlegmon. In spite of its advantages, MR imaging is seldom used to diagnose retropharyngeal abscess, probably owing to easier access to CT in the emergency setting.
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Figure 7a. Abscesses of the retropharyngeal and danger spaces in a 1-year-old girl. (a) Transverse US image shows a hypoechogenic mass (arrow) between the carotid sheath (*) and the vertebral body (VB), a finding that represents a retropharyngeal abscess. (b) Contrast-enhanced CT scan shows two heterogeneous hypoattenuating masses, one in the left retropharyngeal space with peripheral rim enhancement (arrow), and the other on the midline, in the danger space (arrowhead).
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Figure 7b. Abscesses of the retropharyngeal and danger spaces in a 1-year-old girl. (a) Transverse US image shows a hypoechogenic mass (arrow) between the carotid sheath (*) and the vertebral body (VB), a finding that represents a retropharyngeal abscess. (b) Contrast-enhanced CT scan shows two heterogeneous hypoattenuating masses, one in the left retropharyngeal space with peripheral rim enhancement (arrow), and the other on the midline, in the danger space (arrowhead).
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Retrovisceral Space.—
Gastrointestinal duplication cysts are cystic structures that are lined with alimentary tract epithelium, have smooth muscle in their walls, and share a common muscle wall and blood supply with the adjacent gastrointestinal tract (1,13). The lining may be formed by ectopic tissue such as gastric mucosa and pancreatic tissue. Spheric duplications usually do not communicate with the adjacent gastrointestinal tract, but tubular types do. Most duplications manifest during the 1st year of life.
Up to 19% of gastrointestinal duplication cysts are located in the distal esophagus, the second most frequent location (1). Duplications may compress the airways or bleed secondary to ulcerated ectopic gastric mucosa. Esophageal duplications may appear as mediastinal masses at conventional radiography. Esophagography usually shows displacement of the esophagus. The typical appearance of esophageal duplication cysts at US is that of a cystic mass with a wall composed of an inner echogenic layer (mucosa) and an outer hypoechogenic layer (muscle). US is very useful in demonstrating superficial cysts. CT and MR imaging are less specific and demonstrate rounded, fluid-filled masses with contrast-enhanced walls near the esophagus (Fig 8).
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Figure 8a. Esophageal duplication cyst in a 3-week-old boy. (a) Coronal fat-saturated T1-weighted MR image obtained after intravenous injection of gadopentetate dimeglumine shows a hypointense unilocular cyst with a slightly enhancing wall (arrow) close to the esophagus in the right retrovisceral space. (b) On an axial T2-weighted MR image, the cyst appears hyperintense (arrow).
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Figure 8b. Esophageal duplication cyst in a 3-week-old boy. (a) Coronal fat-saturated T1-weighted MR image obtained after intravenous injection of gadopentetate dimeglumine shows a hypointense unilocular cyst with a slightly enhancing wall (arrow) close to the esophagus in the right retrovisceral space. (b) On an axial T2-weighted MR image, the cyst appears hyperintense (arrow).
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Pretracheal Space.—
The pretracheal space extends from the hyoid bone and attached strap muscles to the superior mediastinum and the border of the aortic arch and great vessels. It contains the trachea, larynx, cervical esophagus, recurrent laryngeal nerves, and the thyroid and parathyroid glands. Therefore, diseases of its main components such as thyroglossal duct cyst, goiter, laryngocele, lymphadenopathy, and abscess may be located in this space.
Danger Space
The danger space is a closed space that has been described by various authors as lying between the skull base and the posterior mediastinum, and between the alar and prevertebral fasciae in a sagittal plane. It is considered as a potential pathway for spreading infections (3). Therefore, cellulitis, pus collections, or abscesses (Fig 7b) are the most frequently encountered entities in this space (4).
Prevertebral Space
The prevertebral space contains the prevertebral muscles and extends from the skull base to the coccyx between the prevertebral fasciae and the vertebrae (3).
Carotid Sheath Space
Septic jugular vein thrombophlebitis (Lemierre syndrome) is an uncommon life-threatening anaerobic sepsis that occurs after oropharyngeal infections (14). After an initial tonsillitis and peritonsillar abscess due to an anaerobic gram-negative bacillus of Fusobacterium necrophorum, septic thrombophlebitis of the ipsilateral internal jugular vein with subsequent systemic dissemination may occur. Lemierre syndrome has been reported more frequently in teenagers and young adults but has also been observed in infants and children (15). Color Doppler US may easily show a thrombus of the jugular vein. On axial contrast-enhanced CT scans and two-dimensional reformatted images, the thrombus appears as a hypoattenuating intraluminal filling defect surrounded by contrast material and the jugular vein wall (Fig 9).
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Figure 9a. Septic jugular vein thrombophlebitis (Lemierre syndrome) in a 16-year-old girl. (a, b) Contrast-enhanced CT scans show a peritonsillar abscess (arrow in a) and jugular vein thrombophlebitis with an intraluminal thrombus (arrow in b). (c) Doppler US image depicts the thrombus (arrowheads). The blood flow in the common carotid artery is clearly visible (arrow).
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Figure 9b. Septic jugular vein thrombophlebitis (Lemierre syndrome) in a 16-year-old girl. (a, b) Contrast-enhanced CT scans show a peritonsillar abscess (arrow in a) and jugular vein thrombophlebitis with an intraluminal thrombus (arrow in b). (c) Doppler US image depicts the thrombus (arrowheads). The blood flow in the common carotid artery is clearly visible (arrow).
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Figure 9c. Septic jugular vein thrombophlebitis (Lemierre syndrome) in a 16-year-old girl. (a, b) Contrast-enhanced CT scans show a peritonsillar abscess (arrow in a) and jugular vein thrombophlebitis with an intraluminal thrombus (arrow in b). (c) Doppler US image depicts the thrombus (arrowheads). The blood flow in the common carotid artery is clearly visible (arrow).
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Parotid Gland Space
The parotid gland space contains the parotid gland, the parotid lymph nodes, parts of the external carotid artery, and the retromandibular vein.
Acute salivary gland inflammation is usually viral or bacterial, and chronic inflammation is due to recurrent bacterial infections, autoimmune disease, prior irradiation, or granulomatous disease. Sialodochitis represents inflammation of either the Stensen or Wharton duct, which is dilated secondary to an obstruction near the orifice of the duct. Conditions such as acquired immunodeficiency syndrome, tuberculosis, mycobacterial infections, toxoplasmosis, and sarcoidosis may cause salivary gland inflammation, enlargement, and dysfunction associated with enlargement of lymph nodes inside or outside the parotid gland (3,16). Tumors of the salivary glands are rare in the pediatric age group.
Up to 30% of children infected with human immunodeficiency virus present with parotid gland enlargement due to lymphocytic infiltration and lymphoepithelial cysts (Fig 10). Parotid gland enlargement is often associated with diffuse cervical adenopathy. US may show multiple hypoechoic cysts of varying size and will help distinguish between lymphadenopathy and parotid gland enlargement. At cross-sectional imaging, the cysts are multiple, bilateral, and of varying size and are easily visualized in a contrast-enhanced gland parenchyma (16). In patients with autoimmune diseases, MR sialography has emerged as a substitute for the painful and ionizing conventional sialography (17).
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Figure 10a. Human immunodeficiency virus parotiditis in a 7-year-old girl. Axial US images show multiple hypoechoic lymphoepithelial cysts of varying size (arrows in a) and enlarged lymph nodes (arrow in b). Dotted line and cursors indicate the greatest dimension of one such lymph node.
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Figure 10b. Human immunodeficiency virus parotiditis in a 7-year-old girl. Axial US images show multiple hypoechoic lymphoepithelial cysts of varying size (arrows in a) and enlarged lymph nodes (arrow in b). Dotted line and cursors indicate the greatest dimension of one such lymph node.
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Submandibular Space
Branchial Cyst.—
As mentioned earlier, over 90% of branchial anomalies arise from the second branchial apparatus, with a predominance of cysts. Most second branchial cleft cysts are located in the submandibular space, at the anteromedial border of the sternocleidomastoid muscle, lateral to the carotid space, or posterior to the submandibular gland. They appear as painless fluctuant masses adjacent to the anterior border of the sternocleidomastoid muscle at the mandibular angle (3,6). The cysts usually occur in patients between 10 and 40 years of age, but fistulas or sinuses are more commonly found during the 1st decade of life. The walls of the cysts are usually lined with stratified squamous epithelium overlying lymphoid tissue and occasionally with columnar respiratory epithelium. The intracystic fluid may contain cholesterol crystals.
A second arch cleft cyst is seen at US as a well-marginated, ovoid, hypoechoic mass with a thin wall and occasional fine internal echoes. At CT, it appears as a hypoattenuating mass with a thin wall. MR imaging better depicts the deep-tissue extent of the cyst, which varies from hypo- to isointense on T1-weighted images and is hyperintense on T2-weighted images (Fig 11).
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Figure 11a. Second branchial cleft cyst in a 13-month-old boy. (a) Axial protondensity–weighted MR image shows a hyperintense mass (arrow). (b) Axial US image depicts a hypoechoic lesion containing some slightly echogenic debris (arrow). The lesion is located anterior to the vertebral body (VB) and anteromedial to the carotid sheath space (arrowhead). T = trachea.
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Figure 11b. Second branchial cleft cyst in a 13-month-old boy. (a) Axial protondensity–weighted MR image shows a hyperintense mass (arrow). (b) Axial US image depicts a hypoechoic lesion containing some slightly echogenic debris (arrow). The lesion is located anterior to the vertebral body (VB) and anteromedial to the carotid sheath space (arrowhead). T = trachea.
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Thyroglossal Duct Cyst.—
Thyroglossal duct cysts account for 90% of nonodontogenic congenital cysts. They are seen in the suprahyoid neck in 25% of cases, at the level of the hyoid bone in 15%–50%, and in the infrahyoid neck in 20%–65%. No gender predilection has been reported. About 50% of patients present before 20 years of age, and a second group presents during young adulthood. A thyroglossal duct cyst usually manifests as an enlarging, painless midline mass in a pediatric or young adult patient. Thyroglossal duct abnormalities may be associated with thyroid malignancy in about 1% of patients (80% of the papillary type). Various types of epithelium may line the cyst. Thyroglossal duct cysts may contain epithelial mucosal lining and ectopic thyroid tissue along the course of the duct (1,3,4). US frequently shows a hypoechoic mass with a thin outer line either in the midline of the anterior neck close to the hyoid bone or paramedian within the strap muscles. Heterogeneity seen in the cyst is due to the proteinaceous content of the cyst rather than to inflammation or infection (2,3). At CT, thyroglossal duct cysts appear as well-circumscribed masses with thin walls. The cyst contents have a mucoid attenuation. Peripheral rim enhancement is observed after intravenous injection of contrast material. At MR imaging, an uncomplicated cyst has low signal intensity on T1-weighted images and high signal intensity on T2-weighted images (Fig 12). The wall of the cyst may enhance on T1-weighted images after intravenous injection of gadopentetate dimeglumine.
Masticator Space
According to Mulliken and Glowacki (18), who proposed a classification system based on natural history and cellular structure, vascular malformations are classified on the basis of the predominant type of anomalous vessels as capillary, venous, arterial, and lymphatic malformations. Venous malformations are sometime erroneously classified as cavernous hemangiomas; unlike hemangiomas, however, they do not involute with time and may involve bone. Venous malformations frequently affect the oral cavity, extracranial head, and neck and cause airway compromise due to their size. About 14% of venous malformations involving skeletal muscle occur in the head and neck region. The masseter and pterygoid muscles are most frequently involved, followed by the trapezius and sternocleidomastoid muscles (3,19,20).
Venous malformations are low-flow lesions supplied by small arteries. As a consequence, neither color nor power Doppler US may be able to demonstrate flow in the lesion. However, like second arch cleft cysts, venous malformations are usually seen at US as a well-marginated, ovoid, hypoechoic mass with occasional fine internal echoes. CT shows lesions that are isoattenuating relative to muscle on unenhanced scans and that have variable patterns of enhancement on contrast-enhanced scans. At MR imaging, relative to muscle, venous malformations are either isointense or hyperintense on T1-weighted images and hyperintense on T2-weighted images, with strong enhancement on T1-weighted images after intravenous injection of gadopentetate dimeglumine (Fig 13). The demonstration of venous lakes or phleboliths as hypointense lesions on both T1-and T2-weighted images is more specific.
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Figure 13a. Venous malformation in a 9-year-old boy. Transverse T2-weighted MR image (a) and transverse (b), coronal (c), and sagittal (d) fat-saturated T1-weighted MR images obtained after intravenous injection of gadopentetate dimeglumine show a mass within the right masticator space (straight arrow), with associated infiltration of the superficial fasciae of the lower lip (arrowhead) and deep infiltration of the soft palate (curved arrow in a and b). The mass is hyperintense on the T2-weighted image and demonstrates bright post-contrast enhancement on the T1-weighted images.
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Figure 13b. Venous malformation in a 9-year-old boy. Transverse T2-weighted MR image (a) and transverse (b), coronal (c), and sagittal (d) fat-saturated T1-weighted MR images obtained after intravenous injection of gadopentetate dimeglumine show a mass within the right masticator space (straight arrow), with associated infiltration of the superficial fasciae of the lower lip (arrowhead) and deep infiltration of the soft palate (curved arrow in a and b). The mass is hyperintense on the T2-weighted image and demonstrates bright post-contrast enhancement on the T1-weighted images.
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Figure 13c. Venous malformation in a 9-year-old boy. Transverse T2-weighted MR image (a) and transverse (b), coronal (c), and sagittal (d) fat-saturated T1-weighted MR images obtained after intravenous injection of gadopentetate dimeglumine show a mass within the right masticator space (straight arrow), with associated infiltration of the superficial fasciae of the lower lip (arrowhead) and deep infiltration of the soft palate (curved arrow in a and b). The mass is hyperintense on the T2-weighted image and demonstrates bright post-contrast enhancement on the T1-weighted images.
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Figure 13d. Venous malformation in a 9-year-old boy. Transverse T2-weighted MR image (a) and transverse (b), coronal (c), and sagittal (d) fat-saturated T1-weighted MR images obtained after intravenous injection of gadopentetate dimeglumine show a mass within the right masticator space (straight arrow), with associated infiltration of the superficial fasciae of the lower lip (arrowhead) and deep infiltration of the soft palate (curved arrow in a and b). The mass is hyperintense on the T2-weighted image and demonstrates bright post-contrast enhancement on the T1-weighted images.
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Peritonsillar Space
The peritonsillar space, which is bounded by the capsule of the palatine tonsil and the superior pharyngeal constrictor muscle, may be a site of extension of a quinsy.
Parapharyngeal Space
Rhabdomyosarcoma is a malignant tumor that arises from skeletal muscle cells. Rhabdomyosarcoma is the most common pediatric soft-tissue sarcoma and represents the second most common head and neck malignancy. Three histologic types of rhabdomyosarcoma have been described: embryonal, alveolar, and pleomorphic. Embryonal rhabdomyosarcoma occurs in 60%–77% of cases and frequently involves the head and neck. The parapharyngeal space is less frequently involved than the orbital and sinusal cavities. Embryonal rhabdomyosarcoma is common in younger children. Alveolar rhabdomyosarcoma is seen in older children and has the worst prognosis. Pleomorphic rhabdomyosarcoma occurs most frequently between 2 and 5 years of age and between 15 and 19 years of age and shows a male predilection (21,22). Parameningeal disease carries the worst prognosis, with direct erosion or extension through the skull base foramina to extend into the epidural or meningeal space. US may show the most superficial part of a solid soft-tissue mass with heterogeneous echogenicity, but cross-sectional imaging is always necessary to depict the full extent of the mass and evaluate for possible metastasis. At CT and MR imaging, an inhomogeneous solid mass may be seen (Fig 14). Bone destruction is common, as is intratumoral hemorrhage. The tumor displays strong enhancement with occasional necrotic areas at both CT and MR imaging. Coronal views are especially useful in the staging of lesions eroding the skull base to predict the need for combined craniofacial surgery.
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Figure 14a. Embryonal rhabdomyosarcoma in a 3-year-old boy. Contrast-enhanced CT scans show a solid, heterogeneously hypoattenuating, partially enhancing mass of the right parapharyngeal space. The mass extends laterally toward the mandible (arrow in a) and displaces the carotid sheath space posteriorly (arrow in b).
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Figure 14b. Embryonal rhabdomyosarcoma in a 3-year-old boy. Contrast-enhanced CT scans show a solid, heterogeneously hypoattenuating, partially enhancing mass of the right parapharyngeal space. The mass extends laterally toward the mandible (arrow in a) and displaces the carotid sheath space posteriorly (arrow in b).
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Posterior Cervical Space
Lymphatic malformations in the head and neck result from maldevelopment of the cervical lymphatic system that arises as paired jugular lymph sacs sprouting from the primitive jugular venous plexus at 6 weeks gestation. About 80%–90% of cervical lymphatic malformations are detected by the time the patient is 2 years old. The majority of these lesions occur in the posterior cervical space and the oral cavity (1,3). Lymphatic malformations are classified as either macrocystic or microcystic. Macrocystic lymphatic malformations are more common and are believed to arise from early sequestration of embryonic lymphatic channels. About 80% of macrocystic lymphatic malformations involve the neck and the lower portion of the face. These lesions are frequently infiltrative and do not respect fascial planes. They may extend inferiorly into the axilla and mediastinum or into the floor of the mouth and the tongue (9,10). Lymphatic malformations are formed by multiple cystic spaces lined by endothelial cells separated by minimal stroma. At US, lymphatic malformations manifest as a multilocular, predominantly cystic mass with septa of variable thickness. Echogenic portions representing clusters of abnormal lymphatic channels and fluid levels can be observed. At CT, lymphatic malformations appear as multiloculated hypoattenuating masses. MR imaging allows the best differentiation between lymphatic malformations and the surrounding soft tissues, with the former demonstrating low or intermediate signal intensity on T1-weighted images and hyperintensity on T2-weighted images. The walls of the septa may enhance after intravenous injection of gadopentetate dimeglumine (Fig 15). Infection or hemorrhage can modify the observed signal intensity of the cavities.
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Figure 15a. Lymphatic malformation in a 5-year-old girl. Coronal (a) and axial (b) T2-weighted MR images and an axial fat-saturated T1-weighted image obtained after intravenous injection of contrast material (c) show a multiloculated cystic mass in the left posterior triangle of the neck (arrow). The cysts are hyperintense on the T2-weighted images and demonstrate peripheral wall enhancement on the T1-weighted image.
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Figure 15b. Lymphatic malformation in a 5-year-old girl. Coronal (a) and axial (b) T2-weighted MR images and an axial fat-saturated T1-weighted image obtained after intravenous injection of contrast material (c) show a multiloculated cystic mass in the left posterior triangle of the neck (arrow). The cysts are hyperintense on the T2-weighted images and demonstrate peripheral wall enhancement on the T1-weighted image.
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Figure 15c. Lymphatic malformation in a 5-year-old girl. Coronal (a) and axial (b) T2-weighted MR images and an axial fat-saturated T1-weighted image obtained after intravenous injection of contrast material (c) show a multiloculated cystic mass in the left posterior triangle of the neck (arrow). The cysts are hyperintense on the T2-weighted images and demonstrate peripheral wall enhancement on the T1-weighted image.
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Paravertebral Space
The prevertebral and paravertebral spaces are now considered to be parts of the perivertebral space (3).
Perivertebral Space
Cervical Sporadic Burkitt Lymphoma.—
Burkitt lymphoma is a B-cell non-Hodgkin lymphoma that occurs in two forms. One is an endemic African form, related to endemic Epstein-Barr viral infection. The other form occurs sporadically in the United States and other Western countries. The sporadic form is believed to involve the oral cavity and jaw less commonly than the endemic form, and involvement of the nasopharynx, oropharynx, and cervical lymph nodes is said to be less frequent than in other lymphomas. However, Burkitt lymphoma has one of the shortest doubling times of all solid tumors and may therefore manifest with airway obstruction whatever the initial location and form of the tumor. Infiltration of the neck and pharynx and enlarged nodes are seen in 25% of children with Burkitt lymphoma (Fig 16 ), with the neck and pharynx representing the second most common location (22,23).
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Figure 16a. Cervical sporadic Burkitt lymphoma in a 7-year-old boy. (a, b) Axial T1-weighted (a) and sagittal fat-saturated T2-weighted (b) MR images obtained after intravenous injection of gadopentetate dimeglumine show a contrast-enhanced mass infiltrating the right perivertebral and epidural spaces (arrow). (c) CT scan (bone window) reveals additional infiltration of the C2 vertebral body by the mass (arrow).
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Figure 16b. Cervical sporadic Burkitt lymphoma in a 7-year-old boy. (a, b) Axial T1-weighted (a) and sagittal fat-saturated T2-weighted (b) MR images obtained after intravenous injection of gadopentetate dimeglumine show a contrast-enhanced mass infiltrating the right perivertebral and epidural spaces (arrow). (c) CT scan (bone window) reveals additional infiltration of the C2 vertebral body by the mass (arrow).
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Figure 16c. Cervical sporadic Burkitt lymphoma in a 7-year-old boy. (a, b) Axial T1-weighted (a) and sagittal fat-saturated T2-weighted (b) MR images obtained after intravenous injection of gadopentetate dimeglumine show a contrast-enhanced mass infiltrating the right perivertebral and epidural spaces (arrow). (c) CT scan (bone window) reveals additional infiltration of the C2 vertebral body by the mass (arrow).
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Cross-sectional imaging is always necessary to determine the full extent of the mass and the presence of metastasis. The tumor is isoattenuating relative to muscle at CT and isointense on T1-weighted MR images, with heterogeneous enhancement after contrast material administration. The lesion is generally hyperintense on T2-weighted images. CT and MR imaging are useful for follow-up to monitor the mass and lymphomatous node regression.
Cervical Neuroblastoma.—
Neuroblastoma of the head and neck frequently represents metastasis from neural crest sympathetic precursor cells in the adrenal gland. However, a primary cervical location of neuroblastoma is present in 5% of cases (22). The lesion is usually situated in the cervical lymph nodes, orbit, or skull, with frequent lytic bone involvement. Extension through the intervertebral foramina with dumbbell masses is of particular importance in perivertebral space locations due to possible spinal cord compression and a difficult surgical approach. It may not be possible to distinguish cervical dumbbell masses due to ganglioneuroma from neuroblastoma with imaging alone (24). US, CT, and MR imaging can all demonstrate the superficial extent of a cervical neuroblastoma (Fig 17). Neuroblastomas appear as solid, contrast-enhanced masses at both CT and MR imaging, with occasional calcifications or intralesional cysts (22). However, only MR imaging can depict intraforaminal extension, which can cause extradural cord compression when present. Because of its great sensitivity, iodine 123 metaiodobenzylguanidine scintigraphy may help confirm the neural crest origin of cervical neuroblastoma and helps refine the staging of the lesions.
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Figure 17a. Cervical neuroblastoma in a 3-year-old boy. (a, b) Axial proton-density–weighted (a) and contrast-enhanced T1-weighted (b) MR images show an enhancing mass of the posterior perivertebral space displacing the carotid sheath space anteriorly (arrow). Note also the posterior necrotic zone of the mass (arrowhead in b). (c) Iodine 123 metaiodobenzylguanidine scintigram shows hyperactivity in the right cervical region (arrow), a finding that helps confirm the neural crest origin of the lesion.
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Figure 17b. Cervical neuroblastoma in a 3-year-old boy. (a, b) Axial proton-density–weighted (a) and contrast-enhanced T1-weighted (b) MR images show an enhancing mass of the posterior perivertebral space displacing the carotid sheath space anteriorly (arrow). Note also the posterior necrotic zone of the mass (arrowhead in b). (c) Iodine 123 metaiodobenzylguanidine scintigram shows hyperactivity in the right cervical region (arrow), a finding that helps confirm the neural crest origin of the lesion.
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Figure 17c. Cervical neuroblastoma in a 3-year-old boy. (a, b) Axial proton-density–weighted (a) and contrast-enhanced T1-weighted (b) MR images show an enhancing mass of the posterior perivertebral space displacing the carotid sheath space anteriorly (arrow). Note also the posterior necrotic zone of the mass (arrowhead in b). (c) Iodine 123 metaiodobenzylguanidine scintigram shows hyperactivity in the right cervical region (arrow), a finding that helps confirm the neural crest origin of the lesion.
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Cervical Dermal Sinus.—
About 27% of dermal sinuses occur in the posterior cervicooccipital region, consisting of epithelium-lined dural tubes that connect the skin with the central nervous system or its covering. Associated findings may include meningitis or abscesses of the subcutaneous, epidural, or juxtadural space—in which case emergency surgery is required—as well as bone abnormalities (25,26). US, CT, and MR imaging can all demonstrate the superficial extent of a dermal sinus tract. MR imaging allows the best visualization of intramedullary dermoid and epidermoid tumors, which may become visible only on T1-weighted images after intravenous injection of gadopentetate dimeglumine.
Sternocleidomastoid Muscle Space
Fibromatosis colli is a benign mass of the neonatal sternocleidomastoid muscle that causes torticollis with tilting of the head and rotation of the chin toward the same side. Fibromatosis colli may be caused by venous occlusion leading to fibrosis, by birth trauma, or by in utero torticollis. A non-tender firm mass may be palpated in the muscle, which is usually enlarged during the 1st month with secondary resolution of the mass and torticollis (16,27). US shows a focal mass in the muscle or diffuse enlargement that may be hypo-, iso-, or hyperechogenic (Fig 18) (28). At CT, fibromatosis colli appears as isoattenuating or calcified enlargement of the sternocleidomastoid muscle. MR imaging may also show calcifications or signs of past intramuscular hemorrhage.
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Figure 18a. Fibromatosis colli in a 1-month-old boy. (a, b) Axial (a) and sagittal (b) US images show heterogeneous diffuse enlargement of the left sternocleidomastoid muscle (arrow). Cursors indicate the dimensions of the muscle. (c, d) Comparative axial (c) and sagittal (d) US images show a normal right sternocleidomastoid muscle (*).
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Figure 18b. Fibromatosis colli in a 1-month-old boy. (a, b) Axial (a) and sagittal (b) US images show heterogeneous diffuse enlargement of the left sternocleidomastoid muscle (arrow). Cursors indicate the dimensions of the muscle. (c, d) Comparative axial (c) and sagittal (d) US images show a normal right sternocleidomastoid muscle (*).
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Abstract
LEARNING OBJECTIVES FOR TEST...
