There are various techniques for categorizing the complex anatomy of the neck. Based on anatomic boundaries, the neck is divided into anterior and posterior triangles and suprahyoid and infrahyoid regions. The boundaries of the posterior triangle are the sternocleidomastoid muscle (SCM) anteriorly, the trapezius muscle posteriorly, and the middle third of the clavicle inferiorly. The apex of the posterior triangle is the point at which the sternocleidomastoid and trapezius muscles meet at the occipital bone. The roof of the posterior triangle is formed by the investing layer of the cervical fascia, and the floor consists of the muscles covered by the prevertebral layer of the cervical fascia. The posterior triangle is further divided into supraclavicular and occipital triangles by the inferior belly of the omohyoid muscle. The occipital triangle contains posterior branches of the cervical plexus, the accessory nerve, trunks of the brachial plexus, a portion of the external jugular vein, and cervical lymph nodes. The supraclavicular triangle contains a portion of the subclavian artery, the suprascapular artery, and supraclavicular lymph nodes.

The boundaries of the anterior triangle of the neck are the median line anteriorly, the SCM posteriorly, and the inferior margin of the mandible superiorly. The apex of the triangle is at the suprasternal notch of the manubrium. The roof of the anterior triangle is formed by subcutaneous tissue containing the platysma muscle and the floor is formed by the pharynx, larynx, and thyroid gland. The anterior triangle is further divided into submandibular, submental, carotid, and muscular triangles by the digastric and omohyoid muscles. The submandibular triangle contains the submandibular gland (SMG), submandibular lymph nodes, the hypoglossal nerve, and parts of the facial artery and vein. The submental triangle contains submental lymph nodes. The carotid triangle contains the carotid artery, internal jugular vein, vagus nerve, external carotid artery, hypoglossal nerve, sympathetic trunk, accessory nerve, thyroid gland, larynx, pharynx, cervical lymph nodes, and branches of the cervical plexus. The muscular triangle contains the sternothyroid and sternohyoid muscles, the thyroid gland, and the parathyroid glands.

The boundaries of the nasopharynx consist of the choanae anteriorly, the sphenoid sinus superiorly, the clivus posteriorly, and the soft palate inferiorly. The parapharyngeal space is peripheral to the nasopharynx and is separated from it by the pharyngobasilar fascia, which is the superior extension of the superior constrictor muscle. The infratemporal fossa (masticator space) is lateral to the parapharyngeal space and inferior to the middle cranial fossa. The retropharyngeal space is a potential space between the visceral fascia posterior to the larynx and the prevertebral fascia; it extends from the skull base to the mediastinum. Multiple lymph nodes are located in the retropharyngeal space; these nodes serve lymphatics in the nasopharynx, paranasal sinuses, and temporal bones. The retropharyngeal space is a common site of neck infection (Table 30-1).

The pterygopalatine fossa is located immediately inferior to the skull base, and is bounded anteriorly by the wall of the maxillary sinus, posteriorly by the pterygoid process, and medially by the palatine bone. Important structures within the pterygopalatine fossa include the maxillary branch of the trigeminal nerve, the sphenopalatine ganglion, and the terminal branch of the maxillary artery. On axial CT, the normal pterygopalatine fossa appears as a slit-like, fat-filled space between the posterior walls of the maxillary sinuses and the pterygoid processes at the level of the superior nasopharynx. The pterygopalatine fossa is the site of origin of most juvenile angiofibromas.

The parapharyngeal space is a potential space that is normally fat-filled. It is located immediately lateral to the pharynx, and extends from the base of the skull to the level of the hyoid bone. At the level of the nasopharynx and oropharynx, the parapharyngeal space separates the muscles of mastication from those of deglutition. The parapharyngeal space contains portions of the internal carotid artery and internal jugular vein, and lateral retropharyngeal lymph nodes. On axial images, the superior aspect of the parapharyngeal space has a slit-like configuration; it has a larger triangular shape on more inferior images at the level of the nasopharynx through the mid oropharynx. Inflammation or abscess formation of parapharyngeal lymph nodes is common in patients with tonsillitis.

Velopharyngeal Insufficiency

Velopharyngeal insufficiency can occur due to structural deficiency of the palate, neurological impairment, or faulty learning. Videofluoroscopy during phonation is an important part of the evaluation of these children. This technique allows determination of the location, size, and shape of the velopharyngeal gap, the consistency with which the gap appears, and the pattern of displacement of the velopharyngeal structures during phonation.^1,2

The pattern of velopharyngeal closure on imaging studies can be divided into 3 categories. The coronal pattern refers to predominant constriction by posterior displacement of the soft palate, with minimal contribution by movement of the lateral pharyngeal walls. A Passavant ridge (focal anterior displacement of the posterior pharyngeal wall) may or may not occur with this pattern. The circular pattern refers to constriction by a combination of posterior displacement of the soft palate and mesial displacement of the lateral pharyngeal walls. The sagittal pattern is characterized by mesial displacement of the lateral pharyngeal walls and little contribution to velopharyngeal constriction by movement of the soft palate.

Anomalies of the Tongue

Macroglossia

Macroglossia refers to pathological enlargement of the tongue. An enlarged tongue can cause substantial airway obstruction and interfere with feeding. With severe macroglossia, the tongue constantly protrudes from the open mouth. Airway obstruction in these children produces noisy respirations. Macroglossia is common in children with congenital hypothyroidism, glycogen storage disease, and Beckwith-Wiedemann syndrome (Figure 30-1). Children with Down syndrome have retrognathia that results in prominence of the tongue relative to the small oral cavity. Masses that can cause enlargement of the tongue include lingual thyroid, lymphatic malformation, thyroglossal duct cyst, enteric duplication cyst, hemangioma, and rhabdomyosarcoma (extremely rare) (Figure 30-2).^3,4

Macroglossia appears on lateral neck radiographs as diffuse soft tissue fullness in the oral cavity, usually with posterior extension into the oropharynx. An isolated lesion of the tongue may result in a focal soft tissue density. Apparent soft tissue fullness at the base of the tongue on a lateral neck radiograph should be evaluated with caution, as the normal lingual tonsils or transient posterior positioning of the tongue can simulate a mass (Figure 30-3). When there is a clinical or radiographic suspicion of a mass within the tongue, imaging with MR is usually indicated. Scintigraphy is an effective technique for the diagnosis of lingual thyroid, appearing as a focal ectopic accumulation of radiopharmaceutical at the base of the tongue (Figure 30-4).

Hypoplasia or Aplasia of the Tongue

Hypoplasia or aplasia of the tongue is an extremely rare congenital anomaly. The diagnosis is easily established clinically. Affected infants initially have substantial feeding difficulty, but eventually adapt to the condition and learn to feed with the aid of gravity. Radiographs show lack of normal soft tissue opacity in the inferior aspect of the oropharynx.^5,6

Clinical Presentations: Stridor

Stridor refers to noisy breathing. Stridor is distinct from the rales and wheezing produced by lower airway abnormalities and the sounds created by the vocal cords (e.g., grunting). Stridor results from turbulent airflow at the site of airway narrowing. The character and timing of stridor differ with the anatomic site of the obstruction. Partial airway obstruction within the thoracic cavity typically causes stridor that is more pronounced during the expiratory phase. This is because the obstruction is accentuated by the normal decrease in diameter of the flexible pediatric trachea as the intrathoracic pressure increases during expiration. The cervical portion of the airway undergoes slight decrease in diameter during inspiration, although the effect is less pronounced than the change in the caliber of the intrathoracic segment. Therefore, obstructions above the thoracic inlet often cause stridor that is more prominent during inspiration. Because the larynx is relatively rigid, there is little change in laryngeal airway caliber during respiration; therefore, lesions of the larynx tend to cause biphasic stridor.

Other clinical findings in addition to stridor can help localize the site of airway obstruction in children. Lesions of the glottis and vocal cords sometimes lead to aphonia or hoarseness. Cough can occur with airway obstruction; a barking cough is characteristic of subglottic narrowing and a brassy cough is typical with lesions of the intrathoracic trachea. Epiglottitis tends to cause a raspy cough. Feeding difficulty in a child with stridor suggests the presence of associated pathology such as tracheoesophageal fistula, laryngeal cleft, vascular ring, or neurological disease. Signs of respiratory distress can occur in children (particularly infants) with airway obstruction. The severity of the respiratory distress correlates with the degree of airway narrowing, but not with the location.

The differential diagnosis of stridor includes various congenital and acquired lesions of the airway and adjacent structures (Table 30-2). In infants and toddlers, congenital laryngeal anomalies such as laryngomalacia account for approximately 60% of instances of stridor. Other common causes of stridor in this age group include congenital abnormalities of the trachea, bronchial anomalies, infection, and trauma. Cystic lymphatic malformations can occur in the larynx. Potential neoplasms of the pediatric larynx include hemangiopericytoma and rhabdomyoma.⁷

Stridor can result from a mass within or adjacent to the airway. Subglottic hemangioma is the most common upper airway soft tissue mass to cause obstruction in the neonatal age group, whereas papilloma is the most common airway mass in older children. Other potential tracheal and paratracheal masses include neck abscess, granuloma, neuroblastoma, neurofibroma, lymphoma, and rhabdomyosarcoma. The most common mediastinal vascular anomalies that cause stridor are double aortic arch and right-sided arch with a left ligamentum arteriosum.

Tracheomalacia is a common cause of expiratory stridor in infants. This is due to excessive collapse of all or part of the trachea or main bronchi during the respiratory cycle (Figure 30-5). Although stridor is the dominant finding in most children with tracheomalacia, additional potential clinical features include wheezing, cough, dyspnea, tachypnea, cyanosis, and recurrent respiratory tract infections. The symptoms of idiopathic diffuse tracheomalacia usually resolve spontaneously by 6 to 12 months of age.

Various secondary forms of tracheomalacia also occur. Focal tracheomalacia occurs in nearly all children with esophageal atresia, and symptomatic tracheomalacia typically persists despite satisfactory surgical repair of the esophagus. These children have a characteristic barking cough; stridor, wheezing, and recurrent respiratory infections are common. Vascular rings and congenital heart disease are additional important etiologies of tracheomalacia in children.^8,9

There is an association between tracheomalacia and gastroesophageal reflux. The nature of the association between these 2 conditions is incompletely understood. A common developmental abnormality of the trachea and esophagus is possible. Airway obstruction due to tracheomalacia causes alterations in intrathoracic and intra-abdominal pressures that could potentially exacerbate gastroesophageal reflux. A third theory holds that recurrent tracheal aspiration due to gastroesophageal reflux causes tracheomalacia.^10,11

Stridor, often biphasic, is an important clinical manifestation of tracheal stenosis. Other potential findings include wheezing and cyanosis. The symptoms are exacerbated by activity. Congenital tracheal stenosis is usually due to a complete cartilaginous tracheal ring. Associated anomalies, such as pulmonary artery sling, are common. The great majority of children with congenital tracheal stenosis present as infants. Acquired tracheal stenosis is most often iatrogenic, from an endotracheal tube or tracheostomy (Figure 30-6). Focal extrinsic compression of the trachea can occur from a neoplasm, cyst, vascular anomaly, or dilated esophagus.^8,9,12,13

Tracheal narrowing confined to the subglottic region is an important cause of stridor in children. The mechanisms of congenital subglottic stenosis are varied. Specific anatomic causes include cricoid hypertrophy, a large laryngeal web, and a congenital abnormality of the shape of the cricoid cartilages. The diagnosis of subglottic hemangioma should be considered in neonates with stridor or older infants with clinical episodes that resemble recurrent or intractable croup. Some of these subglottic lesions can be effectively diagnosed with sonography. Standard radiographs and CT also provide useful anatomic information. In general, however, endoscopy is indicated for these children to provide direct visualization of the area.

Congenital anomalies of the great vessels can cause focal tracheal narrowing by extrinsic compression. The most severe of these anomalies is the true vascular ring, with complete encirclement of the trachea and esophagus due to anomalous development of the aortic arch. Other great vessel anomalies, such as pulmonary artery sling, cause tracheal compression without complete encirclement (Table 30-3). The airway symptoms in these children vary with the degree of tracheal compression. Some children are asymptomatic, even with a complete vascular ring. However, substantial tracheal compression typically results in clinical presentation during the neonatal period with respiratory symptoms and stridor. Clinical manifestations of esophageal compression can also occur.¹⁴

Double aortic arch results in a complete vascular ring that typically is associated with symptomatic tracheal narrowing. A right aortic arch with an aberrant left subclavian artery and a left-sided ductus also cause a complete ring, but the tracheal narrowing is usually less severe than that associated with double aortic arch. This anomaly typically includes a diverticulum of Kommerell, which is the dilated proximal segment of the aberrant left subclavian artery. A left aortic arch with an aberrant right subclavian artery does not result in a vascular ring except in the rare instance in which there is a right-sided ductus. The circumflex aorta occurs when the descending aorta is on the side opposite to the arch, and a complete ring is formed when the ductus is ipsilateral to the descending aorta. Pulmonary sling refers to the origin of the left pulmonary artery from the right pulmonary artery, with the vessel passing between the trachea and esophagus. Additional rare great vessel anomalies that can affect the airway are discussed in Chapter 12.

Many congenital vascular anomalies that impact the airway can be detected on high-quality standard chest radiographs. The intrathoracic portion of the trachea should be carefully inspected for any deviation from the normal pattern of slight displacement to the right by the aortic arch on the frontal view and slight posterior bowing of the inferior aspect of the trachea on the lateral view. The trachea is usually deviated to the left in the presence of a right-sided aortic arch or double arch. A vascular ring may cause anterior bowing of the inferior aspect of the trachea when visualized on the lateral projection. The severity of tracheal narrowing varies between patients with vascular rings.

Clinically significant great vessel anomalies are effectively detected with contrast esophagography. A vascular ring causes extrinsic compression of the posterior and lateral walls of the esophagus; a double arch sometimes leads to a “reverse S” pattern (Figure 30-7). Pulmonary artery sling causes deviation of the anterior wall of the esophagus in conjunction with compression of the posterior wall of the trachea. Specific diagnostic evaluation of great vessel anomalies and tracheal compression is provided by MR and CT angiography.

Anomalies of the Larynx

Laryngomalacia

Laryngomalacia is the most common congenital abnormality of the larynx and is the most common cause of stridor in infants. Laryngomalacia is due to weakness of the cartilage in the epiglottis, aryepiglottic folds, and components of the supraglottic aperture. This results in partial collapse of the larynx during inspiration. Flexible endoscopy of these children shows posterior folding of the epiglottis and prolapse of the cuneiform cartilages into the glottis during inspiration.

Infants with laryngomalacia exhibit inspiratory stridor and feeding difficulties. The stridor most often consists of an intermittent fluttering inspiratory noise. The stridor may diminish during crying, and tends to be exacerbated by upper respiratory tract infections or supine positioning of the infant. Symptoms are usually present from birth, but occasionally are delayed until 1 or 2 months of age. As the infant grows, stridor often worsens in severity and then begins to slowly resolve between 6 and 18 months of age. Uncommonly, laryngomalacia causes dyspnea of sufficient severity to substantially compromise feeding.⁷

Standard neck radiographs of infants with laryngomalacia are normal or show nonspecific distention of the hypopharynx and oropharynx with air. Fluoroscopy can be utilized for dynamic evaluation of the airway during the respiratory cycle. Findings during inspiration include: (1) distention of the hypopharynx and oropharynx with air, (2) anterior and posterior displacement of the epiglottis, (3) anteroinferior buckling of the aryepiglottic folds, and (4) paradoxical narrowing of the subglottic trachea.

Posterior Laryngeal Cleft

Posterior laryngeal cleft is a rare anomaly in which there is a communication between the larynx/trachea and the esophagus. This anomaly is due to failure of normal development of the rostral portion of the embryonic tracheoesophageal septum. The prevalence is approximately 1 in 20,000 births. Six percent of infants with esophageal atresia have this anomaly; 20% to 27% of patients with posterior laryngeal cleft have esophageal atresia. There is an association with Pallister-Hall syndrome. Aspiration of swallowed material through the cleft leads to respiratory distress and cyanosis during feeding. Symptoms also occur during episodes of gastroesophageal reflux. These infants are at substantial risk for recurrent aspiration pneumonias.¹⁵

There are 4 types of posterior laryngeal cleft: Type I extends to the vocal cords, type II extends into the cricoid cartilage, type III involves the cervical trachea, and type IV extends into the thoracic trachea. Esophagography shows spillage of contrast from the upper portion of the esophagus into the larynx or larynx and trachea. Careful fluoroscopic observation is essential in order to differentiate this lesion from functional aspiration. Deficiency of the posterior cricoid lamina can be demonstrated in these children with MR.¹⁶

Congenital Laryngeal Stenosis

Congenital laryngeal stenosis is a rare anomaly that results from failure of normal recanalization of the larynx during fetal week 10. The stenosis may be membranous (i.e., laryngeal web) or cartilaginous. Additional classification according to the level of the obstruction is also useful: supraglottic, glottic, or subglottic.

Membranous laryngeal stenosis is the most common form of congenital laryngeal stenosis. Infants with this anomaly typically have inspiratory and expiratory stridor and dysphonia (hoarse cry). With severe involvement, life-threatening airway obstruction may be evident at the time of delivery. Chromosomal and cardiovascular anomalies are common in patients with a congenital laryngeal web; chromosome 22q11 deletion is the most common association.

Cartilaginous laryngeal stenosis most often involves the subglottic region. There is circumferential narrowing of the airway inferior to the vocal cords (vocal folds) at the level of the cricoid cartilage. Affected infants exhibit biphasic stridor. A barking cough similar to that of viral croup may be present, and some patients come to clinical attention due to symptoms of prolonged or recurrent croup. Occasional infants with cartilaginous congenital laryngeal stenosis do not develop overt symptoms until several months of age, when greater activity results in increased ventilatory requirements. If there is severe obstruction, cyanosis may occur in the perinatal period. Cartilaginous laryngeal stenosis is the most common congenital airway lesion that necessitates tracheostomy in infants.

The radiographic appearance of congenital laryngeal stenosis in the subglottic region consists of smooth circumferential narrowing of the air column. The radiographic appearance has considerable overlap with that of croup, acquired laryngeal stenosis, and subglottic hemangioma. Differentiation from croup is possible by fluoroscopic observation of lack of change in the subglottic narrowing during the respiratory cycle; the severity of narrowing increases during inspiration in children with croup. Differentiation from subglottic hemangioma is usually possible on the basis of the circumferential character of the narrowing with congenital laryngeal stenosis. CT provides superior depiction of the stenosis in comparison to standard radiographs.

Membranous laryngeal stenosis cannot be detected with standard radiographs. The diagnosis is usually made by direct visualization or endoscopy. However, this band-like lesion can be demonstrated with laryngeal sonography. Most often, the web is located between the vocal cords anteriorly. Thick webs can extend into the subglottic region and result in symptomatic subglottic stenosis.^17,18

Laryngocele

A laryngocele is an air-filled outpouching of the laryngeal ventricle. The pathogenesis likely involves elevated intraglottic pressure. An infected laryngocele is called a laryngopyocele. Laryngoceles are classified as internal and external types. An internal laryngocele is confined to the interior of the larynx. It arises in the anterior ventricle and extends posterosuperiorly into the supraglottic portion of the larynx. The internal type accounts for approximately 60% of laryngoceles. Most patients with this lesion have stridor. An external laryngocele extends beyond the larynx, usually into the submandibular space. The communication between an external laryngocele and the larynx may be a small tract through the thyrohyoid membrane. If drainage is poor, the cyst may partially or completely fill with fluid. Secondary infection can occur.

A laryngocele typically appears on diagnostic imaging studies as an air-filled laryngeal or paralaryngeal mass with well-defined margins (Figure 30-8). An external laryngocele sometimes contains an air-fluid level. An internal laryngocele and those external laryngoceles that freely communicate with the laryngeal lumen undergo alterations in size with the respiratory cycle; the cyst becomes distended during the Valsalva maneuver. The lack of communication of the lesion with the esophagus and pharynx can be confirmed with an esophagram. Cross-sectional imaging with CT or MR allows more accurate localization of the lesion, and provides characterization of those laryngoceles that are fluid-filled and poorly visualized on radiographs.^19,20

Congenital Laryngeal Cyst

Congenital laryngeal cyst is a rare lesion that can cause neonatal stridor. Other potential symptoms are feeding difficulties, cough, dyspnea, and voice changes. DeSanto et al propose classification of these lesions as ductal cysts, saccular cysts, and thyroid cartilage foraminal cysts (rare).

Ductal cysts presumably result from submucosal gland obstruction. Ductal cysts can arise anywhere in the larynx, but are most common in the valleculae, aryepiglottic folds, and vocal cords. Lateral neck radiographs demonstrate a round or oval soft tissue mass in the hypopharynx, usually at the base of the tongue. CT or MR evaluation confirms the cystic nature. The lesion occasionally extends into the prehyoid space, thereby mimicking a thyroglossal duct cyst (Figure 30-9).^21,22

A saccular cyst is a rare developmental lesion of the larynx that shares some clinical and imaging features with laryngocele. This mucosa-covered lesion, however, is fluid-filled and does not communicate with the laryngeal lumen. An anterior saccular cyst protrudes between the false and true cords, whereas a lateral cyst extends between the false cords and aryepiglottic folds. The pathogenesis may involve distension of the sacculus laryngis. Symptoms result from airway obstruction. Most often, there is inspiratory stridor. Imaging studies demonstrate a nonenhancing intrinsic laryngeal mass. CT, ultrasound, and MR show a thin well-defined wall and homogenous fluid contents.

Vocal Cord Paralysis

Vocal cord paralysis can be congenital or acquired, and unilateral or bilateral. These patients may exhibit biphasic stridor, aphonia, or hoarseness. With bilateral vocal cord paralysis, the cords are apposed and the voice is normal; other manifestations of substantial airway obstruction are present in these patients, however. The infant with unilateral vocal cord paralysis often has a weak cry and signs of mild respiratory distress. Vocal cord paralysis is often due to recurrent laryngeal nerve damage, but can also occur following a direct insult to the cords or with central nervous system (CNS) pathology. Specific causes include birth trauma, neck mass, head injury, CNS anomaly, infection, trauma, surgery, endotracheal intubation, neuromuscular disease, mediastinal mass, and cardiovascular anomaly. The condition is idiopathic in some patients. Bilateral cord paralysis is often associated with a CNS abnormality, such as Chiari II malformation. In the neonate, the most common causes of vocal cord paralysis are birth trauma, brain injury, intracranial hemorrhage, and perinatal asphyxia.

Neck radiographs of children with vocal cord paralysis may show indistinctness of the cords and laryngeal ventricle. Fluoroscopic examination demonstrates paradoxical collapse of the subglottic portion of the trachea during deep inspiration. With unilateral vocal cord paralysis, fluoroscopic examination in the frontal projection shows the paralyzed cord to be in a midline position. The normal cord moves toward the midline during phonation and then retracts during rest, whereas the paralyzed cord fails to retract appropriately during the resting phase. With bilateral vocal cord paralysis, the cords are apposed near the midline and only a narrow slit-like air passage is present.

Sonography is a useful technique for dynamic evaluation of vocal cord function. The normal thyroid cartilage is imaged as an inverted T-shaped hypoechoic structure. The cricoid cartilage appears as a round hypoechoic structure adjacent to the superior aspect of the thyroid gland. The arytenoids are located behind the vocal cords and each has a posterior hypoechoic component and an anterior hyperechoic component. Adduction and abduction of the arytenoids can be observed during phonation. The vocal cords are visualized sonographically as triangular hypoechoic structures. The apex of each cord is located posterior to the thyroid lamina and the base is at the hypoechoic aspect of the arytenoid. Abduction of the vocal cords is best demonstrated during deep inspiration. Vibration of the cords can be observed during phonation. The false vocal cords are located just superior to the true cords; these structures are hyperechoic due to fatty tissue.^23,24

Various patterns of vocal cord dysfunction can be demonstrated with sonography in patients with vocal cord paralysis. Abductor paralysis results in the inability to open the glottis, whereas adductor paralysis limits closure of the glottis. With unilateral paralysis, the injured vocal cord may move passively toward the contralateral side during inspiration. With bilateral paralysis, there is lack of appropriate abduction of the cords during inspiration.^25,26

Anomalies of the Epiglottis

Congenital absence or hypoplasia of the epiglottis is a rare anomaly that most often occurs in association with a syndrome or another developmental lesion. These infants typically suffer repeated episodes of aspiration pneumonia due to lack of epiglottic protection. Inspiratory stridor is also common. The imaging diagnosis is established with standard radiographs, CT, or MR (Figure 30-10).^27,28

Bifid epiglottis also is usually associated with other anomalies, such as polydactyly, midline defects, endocrine disorders, and CNS anomalies. Bifid epiglottis is present in approximately 40% of patients with Pallister-Hall syndrome (congenital hypothalamic hamartoma, hypopituitarism, imperforate anus, polydactyly, and visceral anomalies). Other reported associations include Joubert syndrome and Bardet-Biedl syndrome. The major clinical manifestations of bifid epiglottis are stridor and aspiration.²⁹

An omega-shaped epiglottis is a developmental variation in which the lateral flaps curve downward. Children with laryngomalacia often have a somewhat elongated epiglottis that has an omega configuration. An omega-shaped epiglottis occurs in some children with arthrogryposis multiplex congenita and osteogenesis imperfecta. Most children with an omega epiglottis have no associated symptoms. On a lateral radiograph, the epiglottis appears (artifactually) thickened; observation of normal aryepiglottic folds serves to differentiate this anomaly from epiglottitis (Figure 30-11).³⁰

Developmental Abnormalities of the Trachea

Developmental tracheobronchial lesions include atresia, ectopic bronchial origin, stenosis, duplication, and tracheoesophageal fistula (Table 30-4). The major tracheal anomalies are discussed below. Please refer to the Chapter 1 for discussion of bronchial anomalies.

Tracheal Atresia

Tracheal atresia is an extremely rare anomaly of disordered embryonic tracheal and esophageal separation. There are 3 forms of this anomaly: (1) Most common is a fistulous connection between the carina and the esophagus and complete absence of the trachea; (2) another potential anatomic pattern is connection of a short distal segment of the trachea to the anterior wall of the esophagus; and (3) tracheal atresia without a tracheal or bronchial fistula to the esophagus is exceedingly rare.

Infants with tracheal atresia have clinically obvious respiratory distress at birth and are usually cyanotic. Esophageal intubation provides a pathway for ventilation of these critically ill infants. Surgical ligation of the distal portion of the esophagus prevents escape of air into the GI tract. Despite these maneuvers, however, tracheal atresia is nearly always lethal. Anomalies of other organ systems are common.

The fetal manifestations of tracheal atresia and other severe airway lesions such as laryngeal atresia and tracheal or laryngeal stenosis are termed congenital high airway obstruction syndrome. These conditions result in characteristic findings on prenatal ultrasound: bilaterally enlarged and diffusely echogenic lungs, dilation of airways distal to the obstruction, and fetal ascites and/or nonimmune hydrops.

The sonographic examination of the fetus with congenital high airway obstruction should include a search for additional fetal anomalies that, when combined with tracheal atresia, indicate the presence of Fraser syndrome. Fraser syndrome (cryptophthalmos-syndactyly syndrome) is an autosomal recessive disorder that includes various anomalies, the most common of which are cryptophthalmos and syndactyly. Cryptophthalmos refers to failure of separation of the eyelids, such that skin partially or completely covers the globes. Other potential anomalies in individuals with Fraser syndrome include ambiguous genitalia, polydactyly, ear malformations, microphthalmia, laryngotracheal anomalies, oral clefting, renal agenesis, imperforate anus or anal stenosis, and choanal stenosis/atresia.^31,32

Chest radiographs of the newborn with tracheal atresia and a fistula between the airway and esophagus show distention of the esophagus with air. A small amount of contrast material can be introduced into the esophagus to outline the anatomy. Alternatively, the pathological anatomy can be demonstrated with helical CT (Figure 30-12).^33,34

Tracheal Duplication

Duplication of the trachea is an exceedingly rare anomaly. Both complete and partial forms of tracheal duplication have been reported. Narrowing of the trachea in affected infants typically results in stridor. The diagnosis can be established with high-resolution CT, which shows a hypoplastic tracheal lumen coursing adjacent to the main tracheal lumen.^35,36

Congenital Tracheal Stenosis

The most common form of congenital tracheal stenosis is narrowing of the airway by 1 or more complete cartilaginous tracheal rings. Associated anomalies are common in these children, and include pulmonary artery sling, vascular rings, and various pulmonary anomalies (Figure 30-13). Ninety percent of affected children present during the first year of life. Acquired tracheal stenosis is most often iatrogenic, such as following endotracheal intubation or tracheostomy. An extrinsic compression of the trachea can occur from a neoplasm, cyst, vascular anomaly, or dilated esophagus. Children with tracheal stenosis may present with stridor (often biphasic), wheezing, and cyanosis. The symptoms tend to be exacerbated by activity.⁸

Congenital tracheal stenosis is focal in approximately 50% of affected children, diffuse in 30%, and funnel-shaped in 20%. Focal stenoses can be membranous or cartilaginous. High kilovoltage technique radiographs can be utilized to detect and characterize suspected tracheal stenosis. Helical CT is the most accurate and specific imaging technique for most etiologies of tracheal stenosis (Figure 30-14). This allows documentation of the severity of narrowing, as well as the detection of pathology in adjacent cervical and mediastinal structures (Figure 30-15), (Figure 30-16). The creation of virtual tracheobronchoscopic images from multidetector CT image data provides 3D depiction of airway anatomy in patients with suspected stenosis.^9,12,13,37

Innominate artery compression syndrome is a form of congenital tracheal stenosis or localized tracheomalacia in which there is narrowing along the anterior aspect of the trachea adjacent to the innominate artery. In infants, the innominate artery usually arises from the aortic arch to the left of the trachea and crosses immediately anterior to the trachea; this is sometimes termed an anomalous brachiocephalic artery. The relatively small size and pliability of the infantile trachea apparently predispose the airway to extrinsic compression by this vessel. There is an anatomic and clinical spectrum that ranges from mild asymptomatic narrowing to severe narrowing that causes stridor, dyspnea, or apnea. Normal growth and development of the trachea result in spontaneous resolution of symptoms in most patients. Infants with a dilated upper esophagus, such as those with esophageal atresia, are particularly prone to innominate artery compression syndrome.

Mild anteroposterior narrowing of the trachea at or just below the level of the thoracic inlet is a common radiographic finding in normal infants. Occasionally, this mimics the appearance of compression by the innominate artery. The diagnosis of true innominate artery compression syndrome is suggested by substantial narrowing in a symptomatic patient. Fluoroscopic evaluation may show dynamic respiratory-phase alterations in the degree of compression. MR and contrast-enhanced CT show the narrowing to involve the anterior aspect of the trachea and to occur adjacent to the innominate artery (see Figure 12-14 in Chapter 12).^38,39

Tracheomalacia

Tracheomalacia refers to excessive collapse of all or part of the trachea during the respiratory cycle. All infants have some degree of intrathoracic tracheal collapse during expiration, when the pressure outside the trachea exceeds the pressure inside. The relatively soft composition of the immature trachea allows inward deviation of the walls in response to the extrinsic pressure. This dynamic tracheal collapse is abnormally accentuated in infants with symptomatic tracheomalacia, producing airway obstruction and stridor. Other potential clinical manifestations of tracheomalacia include wheeze, cough, dyspnea, tachypnea, cyanosis, and recurrent respiratory tract infections. Uncomplicated congenital diffuse tracheomalacia spontaneously diminishes in severity as the structural integrity of the trachea improves with maturation, and symptoms often resolve by 6 to 12 months of age.⁸

Tracheomalacia can be divided into primary and secondary forms. Primary tracheomalacia is due to congenital immaturity of tracheal cartilage, with weakness of the supportive cartilage rings as well as hypotonia of the myoelastic elements. Primary tracheomalacia is sometimes associated with connective tissue disorders such as chondromalacia punctata and Larsen syndrome. The underlying causes of secondary tracheomalacia are varied. Tracheomalacia is common in children with esophageal atresia; the mechanism likely involves compression of the developing fetal trachea by the dilated proximal esophageal pouch just above the atretic segment. Tracheomalacia due to great vessel compression of the anterior aspect of the trachea is also a relatively common disorder in infants and children. Secondary tracheomalacia can also occur as a consequence of endotracheal intubation.^9,12,40

The diagnosis of tracheomalacia can be established with fluoroscopic observation of the trachea during inspiration and expiration. These children have excessive (>50%) collapse of the intrathoracic portion of the trachea during expiration. This is usually best demonstrated on the lateral projection (Figure 30-17). Similar findings are present on lateral chest radiographs obtained during expiration (Figure 30-5). In children with tracheomalacia due to a great vessel abnormality, such as left pulmonary artery sling, the tracheal and vascular anatomy can be effectively demonstrated with helical CT or MRI.⁴¹

A variety of surgical techniques are available to treat children with severe symptomatic tracheomalacia. Aortopexy is the most commonly utilized procedure for the treatment of focal tracheomalacia in the distal aspect of the trachea. This consists of suture fixation of the aorta and innominate artery to the posterior aspect of the sternum, thereby relieving great vessel compression of the trachea.⁴² Transcatheter introduction of a tracheal stent is a treatment option for some forms of tracheomalacia.⁴³

Thyroglossal Duct Cyst

Thyroglossal duct cyst is the most common midline mass of the neck in children, accounting for approximately 70% of all congenital neck masses.⁴⁴ This lesion is due to the formation of an epithelial-lined cyst from a remnant of the thyroglossal duct. Thyroglossal duct cysts can occur anywhere from the foramen cecum to the thyroid gland. Approximately 80% of thyroglossal duct cysts are immediately adjacent to the hyoid bone, 20% are suprahyoid, and 2% are intralingual. There is no gender predilection. Carcinoma arising within a thyroglossal duct cyst is a rare complication that can occur in adults and older children; most are papillary carcinomas.⁴⁵

Early during embryonic development, a diverticulum arises from the floor of the pharynx between the first and second branchial arches; this later corresponds to the foramen cecum at the base of the tongue. The diverticulum “descends” in the midline of the neck as the thyroglossal duct. By the seventh week of gestation, the duct reaches the inferior aspect of the neck anterior to the trachea, where it gives rise to the thyroid gland. The thyroglossal duct passes immediately ventral to, or occasionally through, the hyoid bone. Normally, the thyroglossal duct involutes by the 8th to 10th gestational week, but one or more remnants are common.⁴⁶ If there is sufficient epithelial cell activity in a remnant of the duct, a cyst forms. Histological examination of a thyroglossal duct cyst shows stratified squamous epithelium or ciliated pseudostratified columnar epithelium lining the cyst wall.

Although thyroglossal duct cysts can present at any age, most are discovered during the first several years of life. Typically, there is a small palpable anterior mass that is otherwise asymptomatic. Seventy-five percent are at the midline and 25% are paramedian (within 2 cm of the midline).⁴⁷ The lesion may also come to clinical attention due to infection. Repeated infection is a factor in the pathogenesis of cyst formation for some of these lesions. If the duct remnant is patent to the level of the foramen cecum, organisms from the mouth can gain access to the cyst. Antibiotic therapy frequently induces decrease in size of an infected thyroglossal duct cyst. Rarely, a thyroglossal duct cyst in the base of the tongue causes symptomatic airway compromise.⁴⁸ Intralaryngeal extension of a thyroglossal duct cyst can produce hoarseness or other respiratory symptoms. Unlike branchial cleft cysts, a thyroglossal duct cyst does not have an external opening at the skin surface (unless infection progresses to perforation and skin breakthrough). Cephalad motion of the cyst may be noted when the tongue is protruded, due to the connection of the thyroglossal duct with the base of the tongue.⁴⁹

The usual treatment of a thyroglossal duct cyst is surgical excision. The procedure includes removal of the central portion of the hyoid bone as well as an en bloc resection of the soft tissue surrounding the cyst, including tissue along the expected course of the thyroglossal duct (Sistrunk procedure). Recurrence of a thyroglossal duct cyst after the Sistrunk procedure is as high as 15%. The risk for recurrence is greater if there have been infections prior to surgery, a preliminary surgical procedure was performed, the patient age was less than 2 years at the time of the procedure, the lesion was multicystic on histopathology, or multiple thyroglossal tracts were identified at pathological examination.^50,51

Sonography shows a thyroglossal duct cyst as a well-defined mass at or near the midline anteriorly; the characteristic location is the most important factor in the differentiation from other cystic neck masses (Table 30-5). A paramedian thyroglossal duct cyst is often located within a strap muscle, most commonly on the left. As noted above, most of these lesions are located adjacent to the hyoid bone. A projection or beak extending from the cephalad aspect of the cyst is sometimes visible on sonography; this is a remnant of the thyroglossal duct. The echogenicity of a thyroglossal duct cyst varies between patients. The lesion is purely anechoic in a minority of patients, whereas proteinaceous fluid, debris, and septa result in the more common heterogenous or echogenic patterns (Figure 30-18). Compression and release with the transducer show movement of the echogenic contents and help to confirm the cystic nature. Other clues to the cystic composition are acoustic enhancement and lack of color Doppler evidence of perfusion (Figure 30-19). Confirmation of a normal thyroid gland is an essential component of the sonographic evaluation of the child with a thyroglossal duct cyst.^52–56

Scintigraphy with ¹²³I or ^99mTc pertechnetate is typically normal in patients with thyroglossal duct cyst. Any functional thyroid tissue in the cyst or thyroglossal duct is too small to be detected. The utility of scintigraphy is to rule out an ectopic thyroid, and thereby prevent the inadvertent removal of the patient’s only functional thyroid. Although there is some controversy as to whether scintigraphy should be performed in all patients with a suspected thyroglossal duct cyst, sonography alone is generally sufficient for confirming the presence of a normal gland and thereby ruling out an isolated ectopic thyroid. If sonography fails to identify a normal thyroid gland, scintigraphy should be performed to detect ectopic tissue.^54,56,57

A thyroglossal duct cyst appears on CT as a smooth, well-defined mass (Figure 30-20). The wall enhances with IV contrast. A thick, irregular wall suggests superimposed inflammation. The cyst contents are typically uniform. The attenuation values are often slightly above those of clear fluid. Elevated attenuation occurs in some patients due to proteinaceous fluid, particularly if there have been prior infections. Most often, the cyst is adjacent to the hyoid bone, sometimes draping across the bone or causing remodeling. Suprahyoid thyroglossal duct cysts are usually at the midline; the most common location is between the bellies of the anterior digastric muscles.⁵⁸

On MR, a thyroglossal duct cyst often produces homogeneous high signal intensity on T1-weighted images, due to the proteinaceous nature of the fluid (Figure 30-21). The T2 signal intensity in these patients is variable. A minority of patients has a MR pattern of a simple cyst, with low signal intensity on T1-weighted images and high signal intensity on T2-weighted images. The wall of the cyst may enhance with contrast, particularly if there is inflammation; a thick irregular enhancing rim suggests infection. In older patients, a tract to the base of the tongue (the thyroglossal duct) is occasionally visible with MR imaging.^59,60

If imaging studies show a mural nodule or calcification within a thyroglossal duct cyst, the possibility of associated carcinoma should be considered. Papillary thyroid carcinoma is the most common type.⁶¹ The solid neoplastic component of the thyroglossal duct cyst may enhance prominently with IV contrast. Calcification, when present, is irregular.⁶² Careful imaging evaluation of the thyroid gland is imperative in these patients, as a second tumor focus within the thyroid can accompany carcinoma of a thyroglossal duct cyst.⁶³

Branchial Cleft Anomalies

Branchial cleft anomalies (also termed branchial apparatus anomalies) include cysts (75%), sinuses, and fistulae. Small superficial cartilaginous remnants with skin tags can also occur. A fistula is a tubular structure that has both internal pharyngeal and external cutaneous openings. A sinus is a blind-ending tract with an opening from the skin (i.e., an external sinus) or from the pharynx (an internal sinus). Cysts can be spherical, ovoid, or tubular, but do not communicate with the skin or pharynx. As a group, branchial cleft anomalies are about one-third as common as thyroglossal duct cysts. Branchial cleft cysts account for 15% to 20% of neck masses in children.⁶⁴

Early in embryogenesis, there are 6 transverse mesodermal bars (arches) in the developing neck that are separated by 5 clefts. Each of these branchial clefts contacts an adjacent outpouching from the pharynx (pharyngeal pouch), with separation only by a thin membrane. The second, third, and fourth clefts coalesce later in embryogenesis to form a common chamber called the cervical sinus of His. This process involves caudal growth of the second branchial arch, which overlaps the third and fourth clefts. Because of this pattern of development, anomalies arising from the second branchial cleft can occur throughout the neck. The first branchial cleft is involved in the development of the eustachian tube, tympanic cavity, mastoid antrum, tympanic membrane, and external auditory canal. The second cleft gives rise to the palatine tonsil and tonsillar fossa. The third cleft forms the thymus, inferior parathyroid glands, and pyriform sinuses. The fourth cleft participates in formation of the superior parathyroid glands and the apices of the pyriform sinuses.⁶⁵

Branchial cleft cysts can present at any age; the second decade is the most common age at diagnosis. Unless infected, the clinical presentation of a branchial cleft cyst is that of a nontender upper neck mass that is only slightly movable with palpation. Sizes range from 1 to 10 cm. Displacement of the cyst by enlarged adjacent lymph nodes may increase its conspicuity during an acute respiratory infection. Bacterial infection of a branchial cleft cyst can occur if organisms gain entry via a fistula or sinus. The differential diagnosis of a branchial cleft cyst includes lymphatic malformation, abscess, thyroglossal duct cyst, submandibular gland cyst, ranula, inflammatory lymphadenopathy, and necrotic tumor.

The skin opening of a branchial cleft fistula or external sinus most often is along the lower third of the anterior border of the SCM (sternocleidomastoid muscle). The opening is typically pinpoint in size, and exudes mucoid material. Bilateral lesions occasionally occur (approximately 2%). Because the tract is a portal of entry for pathogens, clinical manifestations of infection are sometimes present. Most branchial cleft anomalies with an external opening are clinically recognizable during infancy.

Approximately 95% of branchial cleft anomalies arise from the second cleft. These are most often located at the anterior border of the SCM, near the angle of the mandible (Table 30-6). Branchial cleft cysts account for approximately 75% of second branchial cleft anomalies. Other lesions include fistulae between the pharynx and neck, sinus tracts opening to the skin, and internal sinuses arising from the tonsillar fossa, pyriform sinus, or vallecula. Cysts of the second branchial cleft arise along a path extending from the anterior margin of the superior aspect of the SCM to the tonsillar fossa. The Bailey classification divides cysts of the second branchial cleft into 4 types along this path: (I) a superficial cyst adjacent to the anterior surface of the SCM, just deep to the platysma muscle; (II) a slightly deeper cyst located along the anterior-medial surface of the SCM, lateral to the carotid space and posterior to the submandibular gland (SMG); (III) extension of the cyst medially between the carotid artery bifurcation to the lateral pharyngeal wall; and (IV) a cyst in the pharyngeal mucosal space just deep to the palatine tonsil, sometimes with superior extension toward the skull base. The type II cyst is most common; the type IV cyst is least common.⁴⁹

Anomalies of the first branchial cleft occur along the embryonic tract that extends from the submandibular region, through the parotid gland, and into the external auditory canal. Typical clinical presentations include recurrent abscesses or a draining sinus from the ear, periauricular swelling in the parotid area, or an abscess or persistent sinus tract in the neck located above a horizontal plane passing through the hyoid bone.⁶⁶ The 2 most common first branchial cleft cysts are (1) a duplication of the membranous external auditory canal, presenting as a cystic mass anterior and inferior to the ear lobe; and (2) an anomalous external auditory canal with deformity of the ear cartilage, presenting as a large cystic mass over the parotid and upper neck.^67,68

Malformations of the third and fourth branchial clefts are quite rare. These include sinuses, fistulae, and deep cysts.⁶⁹ There is a strong predilection for a left-sided location. Most third branchial cleft cysts are located in the posterior cervical space. Despite the rarity of this lesion, it is the second most common congenital cyst at this location, after lymphatic malformation (cystic hygroma). A third branchial cleft cyst can also occur in the inferior aspect of the neck adjacent to the anterior border of the SCM. Most fourth branchial apparatus anomalies are sinuses rather than cysts or fistulae. The lesions are located along the embryonic tract that extends from the pyriform sinus, through the thyrohyoid membrane, and along the tracheoesophageal groove into the mediastinum. An ectopic parathyroid gland can occur in association with an anomaly of the third or fourth branchial cleft. A sinus or fistula arising from the pyriform sinus frequently involves the thyroid gland (nearly always on the left), and may lead to suppurative thyroiditis.⁷⁰

Radiographs of a child with a branchial cleft cyst are usually normal, or show nonspecific soft tissue fullness. Effects on the airway are uncommon, except with a large lesion. The location and character of the lesion can be demonstrated with sonography. The lesion is usually anechoic or hypoechoic, with a thin well-defined wall (Figure 30-22). However, cholesterol crystals, keratin, cellular debris, or secondary infection can result in increased echogenicity or even a pseudosolid appearance. The mass is compressible, and has acoustic enhancement. The wall of an infected branchial cleft cyst is frequently thickened, and the sonographic differentiation from a lymph node abscess may not be possible.⁷¹

CT shows a branchial cleft cyst as a unilocular or multilocular cyst with a thin uniform wall (Figure 30-23). The contents usually have similar attenuation as water. The wall undergoes only minimal enhancement with IV contrast. With superimposed infection, the contents of the cyst produce higher attenuation values than clear fluid, the wall becomes thickened and irregular, and the wall undergoes prominent enhancement (Figure 30-24). A pathognomonic cross-sectional imaging appearance of a type III second branchial cleft cyst is that of a thin-walled cyst located posterior to the mandible and anterior to the SCM, with a beak extending between the internal and external carotid arteries; there is anterior displacement of the SMG. A first branchial cleft cyst usually appears as a cystic mass within or immediately adjacent to the parotid gland; the findings typically do not allow differentiation from other types of parotid cysts. A third branchial cleft cyst is identified as a unilocular cyst in the posterior cervical space.^49,68,72

The anatomic features of a branchial cleft cyst are accurately demonstrated with MRI (Figure 30-25). As with other cross-sectional imaging techniques, there is a well-defined cyst wall, unless there is current infection or scarring from a prior infection. In most patients, the cyst contents produce low signal intensity on T1-weighted images and high signal intensity on T2-weighted images. However, blood, protein, or cholesterol crystals can result in higher signal intensity on T1-weighted images. Occasionally, there is a septum within the cyst. MRI allows documentation of a location within the carotid sheath for some second branchial cleft cysts.⁷³

Most branchial cleft fistulae and external sinuses do not require radiographic investigation unless there is a palpable mass that suggests an associated cyst. In selected patients with a fistula or sinus, imaging is useful for preoperative planning. Fistulae and external sinuses can be evaluated radiographically by cannulating the orifice at the skin surface and injecting water-soluble contrast material (Figure 30-26).⁷⁴ This procedure does, however, carry a risk of iatrogenic infection. CT or MR may show inflammatory soft tissue infiltration and/or abscess formation along the course of a sinus or fistulous tract. Air is sometimes visible within the lumen of the tract. Inflammatory obstruction of the distal portion of a branchial cleft sinus can lead to dilation of the tract proximally (Figure 30-27).⁷⁵

Surgical treatment of branchial cleft anomalies is usually indicated to prevent infectious complications. Recurrences are common if surgical removal of branchial cleft tissue is incomplete. Chemocauterization is an alternative technique for the treatment of fistulae and sinuses.⁷⁶

Pyriform Sinus Fistula

Pyriform sinus fistula is a rare persistent embryological third or fourth pharyngeal pouch, in which a tract extends from the apex of the pyriform sinus to the inferior aspect of the neck in the thyroid region. If an external opening is lacking, the lesion is more properly termed a sinus rather than a fistula. The tract sometimes extends through the thyroid gland. Most (>90%) pyriform sinus fistulae are located on the left. The lesion usually comes to clinical attention because of symptoms related to a secondary infection; most patients present during childhood. Infection of a pyriform sinus fistula usually leads to drainage from the skin opening. Patients may develop a neck abscess or suppurative thyroiditis; unexplained suppurative thyroiditis in a child should prompt investigation for a possible underlying fistula.^77,78

Pyriform sinus fistula/sinus is best demonstrated with a contrast study utilizing swallowed barium or water-soluble contrast (Figure 30-28). The fistula extends from the apex of the pyriform sinus toward the thyroid gland. Sometimes, there is a skin opening along the inferior aspect of the neck. In cooperative children, the “trumpet maneuver” can help force contrast or air into the narrow tract. A false-negative study may occur if the walls of the fistula are edematous due to infection. The origin of the fistula in the pyriform sinus is sometimes visible with endoscopy; this technique is particularly useful if a contrast study is normal and there is a strong clinical suspicion. CT, MRI, and sonography provide useful diagnostic information in selected cases. Passage of air into the tract during the trumpet maneuver is useful for visualization of the fistula with CT.^75,79–81

Congenital Thymic Cyst

Congenital cervical thymic cyst is a rare lesion that is part of the differential diagnosis of a neck mass in a child. This lesion is most likely due to remnant tissue from the embryonic caudal migration of the primordia of the thymus. The primordia of the thymus arise from the third pharyngeal pouches, fuse medially, and lose their connections with the pharynx. The “descent” of this tissue from the pharynx to the mediastinum (the thymopharyngeal duct) provides the potential for remnant tissue to form a cyst. The cyst is usually located laterally, anywhere from the angle of the mandible to the manubrium. This rare lesion is often misdiagnosed as a branchial cleft cyst or cystic lymphatic malformation.⁴⁹

Congenital thymic cyst of the neck is usually identified clinically as an otherwise asymptomatic palpable neck mass. A large lesion in a neonate may be associated with respiratory distress. Older patients occasionally exhibit stridor, hoarseness, or dysphasia. About two-thirds of congenital thymic cysts present during the first decade of life. They are slightly more common in males. Most often, the lesion is static or slowly enlarging; sudden enlargement may be elicited by hemorrhage or infection. Occasionally, the mass appears to enlarge during the Valsalva maneuver.

Congenital thymic cysts occur in the same portions of the neck as third and fourth branchial cleft cysts. Pathological differentiation of these lesions is based on the demonstration of thymic tissue in the former. Congenital cervical thymic cysts are unilocular and thin-walled. The cyst fluid is thin, and sometimes contains lymphoid aggregates and cholesterol crystals.

Congenital thymic cyst is identified with imaging studies as a cystic mass, most often unilocular and located adjacent to the SCM in the region of the carotid space. The cyst is usually round or oval; occasionally, it appears as an elongated lesion that follows the expected course of the thymopharyngeal duct. Extension into the mediastinum is sometimes present; this is important information for preoperative planning. The thin cyst fluid is hypoechoic on sonography, low attenuation on CT, hypointense on T1-weighted MR images, and hyperintese on T2-weighted images. The proper diagnosis is suggested on CT and MR by a characteristic association with the carotid sheath.^82,83

Ectopic Thymus

Thymic tissue in the neck can occur due to upward herniation of the gland or ectopic/aberrant foci along the embryonic pathway of descent. The most common location is the inferior aspect of the neck. Rarely, intrathyroidal ectopic thymic tissue mimics a neoplasm. On cross-sectional imaging studies, the anomalous tissue usually has identical characteristics to those of the orthotopic thymus (Figure 30-29). The tissue may or may not connect to the orthotopic thymus.⁸⁴

Dermoid Cyst

Teratomatous cysts of the neck include epidermoid cyst, dermoid cyst, and cystic teratoma. Each of these developmental lesions has a peripheral ectodermally derived squamous epithelial component, and may contain keratinaceous material within the lumen. The wall of a dermoid cyst contains skin appendages such as hair follicles, sweat glands, and sebaceous glands, whereas an epidermoid cyst does not. Both of these lesions arise from trapped pouches of ectoderm or from failure of surface ectoderm to separate from the neural tube. Teratomas are true neoplasms that arise from misplaced embryological germ cells, and contain tissues that either derive from more than 1 of the embryonic germ layers or are foreign to the site of the lesion. Teratomas have a heterogenous composition, but occasionally are predominantly cystic. Dermoid cyst is by far the most common of the teratomatous cysts that occur in the neck.^49,85,86

Dermoid cysts of the neck most often are located adjacent to or superior to the hyoid bone. The differential diagnosis of a mass at this location includes a thyroglossal cyst, an epidermoid cyst, and an enlarged lymph node. Compared to the deeper thyroglossal duct cyst, a dermoid cyst is typically subcutaneous and is therefore mobile when palpated. In addition, a thyroglossal duct cyst usually moves when the tongue is protruded, whereas a dermoid does not change position with this maneuver. Lymphadenitis is suggested by local inflammatory signs, but subacute or chronic adenopathy may be difficult to distinguish from a congenital cyst or a neoplasm. Simple excision is the appropriate treatment for a dermoid cyst, whereas a thyroglossal duct cyst requires more extensive dissection.⁸⁷

Sonography of a dermoid cyst usually shows a well-defined unilocular lesion. Because a dermoid cyst contains fat and keratin, it is usually echogenic on sonography. The contents of a large lesion may be quite heterogenous. An epidermoid cyst contains clearer fluid than most dermoids, and therefore usually has a hypoechoic character. A cystic teratoma may contain debris or hemorrhage, septations are common, and the walls may be irregular.

CT of a cervical dermoid cyst shows a unilocular, thin-walled mass. Calcification of the wall is an occasional finding. The appearance of the central aspect varies with the character of the lesion. The most common pattern is homogenous material that produces attenuation values approximately equal to or slightly greater than those of clear fluid. Coalescence of fat into small nodules within a fluid matrix sometimes results in a “sack of marbles” pattern that is highly specific for this lesion. Other possible findings include a disorganized heterogeneous character or fluid–fluid levels. An epidermoid cyst has a homogeneous, low-attenuation appearance. The diagnosis of a cystic teratoma is suggested if the solid portions of the mass contain calcifications or fat.

MRI also shows a dermoid cyst to be a unilocular, well-defined lesion. The signal characteristics of the contents vary between patients, and are largely determined by the complex protein and fat content. Most often, the lesion is of equal or greater signal intensity than muscle on T1-weighted images. Dermoids produce high signal intensity on T2-weighted images. The fibrous capsule is of intermediate signal intensity and enhances to a similar degree as other soft tissue structures. A teratoma usually has a complex consistency on MR, including components with fat signal.

Cervical Bronchogenic Cyst

Cervical bronchogenic cyst is a very rare lesion that is a component of the differential diagnosis of a cystic neck mass in a child. This lesion results from anomalous foregut development. The usual clinical presentation is that of a mass or draining sinus in the suprasternal notch or supraclavicular region. This lesion is more common in males. Histological examination shows the cyst wall to be lined with columnar ciliated pseudostratified epithelial tissue.⁴⁹

Fibromatosis Colli

Fibromatosis colli (congenital muscular torticollis; congenital fibromatosis of the sternocleidomastoid; congenital wryneck) refers to idiopathic fibrosis of the sternocleidomastoid muscle (SCM). The 2 most commonly proposed mechanisms for this condition are (1) injury to the SCM during birth, resulting in subsequent fibrosis of the muscle and (2) a prenatal vascular occlusive event due to fetal malposition that causes edema, muscle fiber degeneration, and fibrosis. Approximately 40% of infants with fibromatosis colli have a history of a difficult delivery. However, this lesion does occur in infants who have been delivered atraumatically by cesarean section.

Although considered a congenital lesion, fibromatosis colli can be clinically silent in the neonate. The clinical features become manifest during the first few months of life in nearly all affected patients, however. The involved SCM is tight and pulls the head toward the involved side. The chin is turned toward the opposite side. Clinical examination shows restricted range of neck motion. In many patients, the affected SCM is palpably enlarged or a neck mass is identified due to fibrosis and contracture of the muscle. The mass is nontender, firm, and mobile beneath the skin surface. Craniofacial deformities develop if the restriction is not released. The deformities of the cranium and skull base (plagiocephaly) occur early in infants with uncorrected torticollis, whereas associated facial bone deformities occur in the childhood stage.^88–90

The clinical diagnosis of fibromatosis colli is not always straightforward, and the condition may be confused with other causes of a neck mass or torticollis. In about half of infants with fibromatosis colli, a SCM mass is not identifiable on physical examination despite the presence of torticollis. In other patients, there is a palpable mass, but the other clinical features are subtle or unrecognized. The differential diagnosis of congenital torticollis includes Klippel-Feil anomaly, unilateral atlantooccipital synostosis, unilateral basilar impression, unilateral occipital condyle hypoplasia, odontoid anomalies, CNS lesion, and pterygium colli (skin web). The differential diagnosis of a lateral neck mass in an infant includes inflammatory lymphadenopathy, fibrodysplasia ossificans progressiva, hemangioma, lymphatic malformation, teratoma, lipoblastoma, rhabdomyosarcoma, and metastatic disease.

An appropriate and timely diagnosis of fibromatosis colli is essential to allow prompt initiation of therapy (which usually prevents progression to substantial craniofacial deformity) and to prevent a mistaken diagnosis of neoplasm. A regimen of stretching exercises is the most common form of treatment for infants with fibromatosis colli. Positive outcomes occur in over 90% of infants treated in this manner, particularly when therapy is started early in life. Rupture of the SCM occasionally occurs during manipulation of the neck in these children; this can be confirmed with sonographic examination. The long-term clinical outlook, however, is favorable despite this unintentional muscle injury. Less than 10% of children with fibromatosis colli require surgical intervention to release the tightened muscle. Botox injection to relax the tight muscle is used by some practitioners.⁹¹

Standard cervical spine radiographs of infants with torticollis serve to detect underlying structural defects of the cervical spine or skull base. With fibromatosis colli, the cervical spine is structurally normal. A specific diagnosis of fibromatosis colli is provided by sonography, CT, or MR. When the diagnosis is entertained clinically, sonography is the most appropriate confirmatory imaging technique. The typical sonographic appearance of fibromatosis colli consists of a focal area of enlargement of the SCM, usually in the midportion (Figure 30-30). The superior and inferior margins of the “mass” taper into the normal portions of the muscle (Figure 30-31). The enlarged portion of the muscle may have echogenicity that is less than (most common), equal to, or greater than normal muscle.^92,93