Anomalies of the Branchial Apparatus
Branchial apparatus anomalies comprise a heterogeneous group of congenital malformations stemming from incomplete in utero resorption of pharyngeal clefts and pouches. Fistulae, cysts, sinus tracts, and cartilaginous remnants are all clinical manifestations arising from these embryonic events. Although all of these lesions are present at birth, many do not become clinically apparent for months or years. In many cases infection is the initial manifestation. Cysts developing from branchial structures usually appear later in childhood than sinuses, fistulae, and cartilaginous remnants, which are observed in infancy. Complete fistulae are more common than external sinuses, and during childhood both are more common than branchial cleft cysts. The incidence of these anomalies in adults is quite different, with cysts occurring more frequently than either sinuses or fistulae.
The term branchial is derived from the Greek word brankhia, meaning gills. The first description of a cervical fistula is credited to Hunczowski in 1789. In 1832, Von Ascherson described the embryonic origin of fistulae arising from the branchial apparatus. A more in-depth understanding of these lesions has been derived from studies conducted by of a number of renowned embryologists of the 19th and early 20th centuries (Proctor, Wilson, Lyall, Stahl, and Frazer).
Four pairs of branchial arches, clefts, and pharyngeal pouches appear in the head and neck region during the fourth to eighth weeks of gestation (Fig. 15-1). At this early stage of development, the clefts are external ectodermal infoldings (resembling the gills of a fish) between the arches and are matched internally by pharyngeal endodermal pouches. This branchial apparatus develops into many of the structures of the lower face and neck.
Five-millimeter human embryo at the fifth week of gestation (inset). Schematic representation of the head and neck region demonstrating the branchial clefts and pouches at the 5-mm embryo stage. Sagittal sections taken through the branchial apparatus depict the location of the external clefts and the internal pouches. The embryonic derivation of important head and neck structures within this region is noted.
As the embryo grows, the arches coalesce and obliterate all of the clefts except for a portion of the first, which becomes the eustachian tube and the auditory canal (Fig. 15-1). The first branchial arch forms the mandible and contributes to the maxillary process of the upper jaw. Abnormal development of this arch results in a wide range of facial deformities, including cleft lip and palate, an abnormal shape or contour of the external ear, and malformed internal ossicles; these deformities comprise 8% of branchial cleft anomalies. The second branchial arch forms the palatine tonsil, the tonsillar fossa, and the hyoid bone. Ninety percent of branchial abnormalities arise from the second cleft. These abnormalities are thought to be due to incomplete obliteration as the first arch overgrows the second, third, and fourth clefts and fuses with the lateral branchial wall. The third arch gives rise to the inferior parathyroid glands and the thymus (Fig. 15-1). The fourth branchial arch stops higher in the neck to form the superior parathyroid glands. The ventral portion of this arch also forms the ultimobranchial body, which is responsible for the development of the thyrocalcitonin-producing parafollicular cells of the thyroid gland. Anomalies of the third and fourth clefts and pouches occur but are rare.
Anatomy and Pathologic Variants
Anomalies of the Branchial Clefts.
First branchial cleft remnants occur along a line extending from the external auditory canal to a point just below the midportion of the mandible. If external openings are present, they are generally found below the mandible and above the hyoid bone (Fig. 15-2). The fistula courses upward to a connection with the external auditory canal. First branchial cleft anomalies include sinuses opening onto the skin or into the pharynx; fistulae with communications between the skin and the pharynx; and cysts without extension to either surface.
Regions of the neck where first, second, and third branchial cleft fistulae or cysts are most commonly seen.
Second branchial cleft lesions most commonly appear as cysts or external openings along the anterior border of the sternocleidomastoid muscle, usually near the junction of the caudal and middle third of the muscle (Fig. 15-2). Those with an external opening typically have a history of drainage of clear mucus. The fistula courses upward along the carotid sheath, between the external and internal carotid arteries, in front of the hypoglossal nerve, and ends in the tonsillar fossa. A fistulagram can demonstrate the course of the tract but is generally not essential for future operative planning.
A third branchial cleft fistula is very uncommon. It generally is seen as an external opening along the anterior border of the clavicular head of the sternocleidomastoid muscle; it may occur in the same areas as lesions of the second cleft but ascends posteriorly to the carotid artery rather than through the bifurcation (Fig. 15-2). The fistula pierces the thyrohyoid membrane and enters the pyriform sinus. Related but distinct embryonic pyriform sinus lesions are also thought to be derived from the third or fourth branchial pouch and will be discussed in more detail in a following section of this chapter.
While a definitive case of a complete fourth branchial cleft fistula has not been documented, based on our understanding of human embryology, such a fistula would course from a low anterior cervical external opening into the chest. Here it would encircle either the subclavian artery on the right or the aortic arch on the left and would then ascend to a connection with the cervical esophagus or pyriform sinus.
Anomalies of the Branchial Pouches.
Although significant anomalies of the first pouch are rare, minor anomalies are common in association with first branchial arch aberrations. The second branchial pouch is involved in the development of the palatine tonsils, and it sometimes persists as an internal sinus. This structure is a blind tract of varying depth within or close to the palatine tonsil, which might be a factor in recurrent tonsillitis. Failure of development of the third and fourth branchial pouches results in the absence of the thymus and parathyroid glands (DiGeorge syndrome), which is involved in neonatal tetany and impaired cellular immunity. An infection might first arise as an inflammatory mass on the anterior lower neck and then fistulize through a tract that runs directly from the skin to the pyriform sinus. The external exit is generally in the lower neck in the region of the thyroid gland. The differential diagnosis of recurrent abscesses of the anterior neck must thus consider a persistent third branchial pouch. Other anomalies arising from the third and fourth branchial pouches may appear as cystic structures in the neck. Cervical thymic cysts (discussed later in this chapter) are generally found on the left side of the neck but may be seen anywhere along the migratory path of descent of the thymus and the pharynx to the anterior mediastinum. Parathyroid cysts can be located anywhere around the thyroid gland or in the mediastinum.
Anomalies of the Branchial Arch Remnants (Cartilages).
Most branchial arch remnants disappear, with the exception of those that contribute to bony structures or ligaments. Occasionally, however, remnants persist as small, triangular masses deep in the skin along the anterior border of the sternocleidomastoid muscle. They present cosmetic problems only and are easily removed.
Clinical Presentation and Evaluation
Most branchial cleft lesions can be diagnosed from a medical history and by performing a physical examination. When a sinus is present, lesions are diagnosed in the first decade of life. However, when there is no external sinus, the diagnosis may not be made until the patient is well into adolescence or adulthood.
Branchial cleft sinuses and fistulae are bilateral in 20% of cases and have a slight female preponderance. An external sinus or fistula is manifested by intermittent clear mucoid drainage from a skin ostium located in the midneck along the anterior border of the sternocleidomastoid muscle (Fig. 15-3A and B). In some cases, the tract itself may be palpable. Preoperative probing of the tract or injecting it with a colored dye or water-soluble contrast should be avoided because it may lead to infection, thus making excision more difficult and recurrence more likely. Familiarity with the cited embryology should help one to identify the branchial cleft origin and its likely associated tract. The diagnosis is often apparent on examination, rendering further radiographic evaluation unnecessary. Internal sinuses drain into the tonsillar fossa and appear as a mass or an inclusion cyst when the draining tract becomes obstructed.
A. Child with a second branchial cleft cyst and a fistula on the opposite side of the neck (arrow). B. Mucoid secretion from a second branchial cleft fistula tract.
Branchial cleft cysts appear after infancy. They are located higher in the neck than the external ostia of sinuses and fistulae, and can be identified as a palpable mass at the level of the carotid bifurcation (Fig. 15-4A and B). They may be more difficult to diagnose, as they tend to lie deep to the anterior border of the sternocleidomastoid muscle in its upper third. These cysts can occur when the cutaneous opening of a sinus tract becomes occluded. It is not unusual for a branchial cleft cyst or sinus tract to become secondarily infected, and it may be the infection that initially alerts the physician to the lesion. Branchial cleft cysts can be confused with and should be distinguished from macrocystic lymphatic malformations (formerly called cystic hygromas), hemangiomas, lymphadenopathy, and particularly, lymphatic or metastatic tumors.
A. Child with a second branchial cleft cyst. B. The cyst is exposed at surgery.
When the diagnosis is uncertain, ultrasonography can be extremely useful in identifying deep cysts and characterizing their contents, as well as in differentiating solid and cystic masses. Additionally, real-time ultrasonography with Doppler imaging can identify associated vascular structures. The extensive differential diagnosis of a mass at the angle of the jaw includes adenopathy, macrocystic lymphatic malformations, dermoids, and parotid lesions, as well as primary and metastatic neoplasms of lymphatic origin. Further diagnostic studies with computed tomography, magnetic resonance imaging, or fine-needle aspiration biopsy may be indicated, particularly for solid masses. Determination of the specific etiology of the mass, however, often requires surgical exploration. Incision and drainage are sometimes necessary. In such cases, it is important to keep in mind that branchial cleft anomalies are anatomically related to nerves and vessels that are vulnerable to injury during drainage procedures.
Because of the likelihood of infection developing in any of the branchial lesions, complete excision of the cyst and sinus tract is generally recommended at the time of diagnosis in a noninfected lesion. Surgery in infants is delayed until 3 to 6 months of age to minimize the risks of anesthesia associated with neonatal surgery. In older children, surgical procedures are scheduled conveniently to minimize the risk of intervening infection. Infected cysts and sinus tracts should be treated with appropriate antibiotics and warm soaks. If they are fluctuant, needle aspiration or incision and drainage should be performed and definitive resection deferred until the infection has completely resolved. Attempts at complete excision during active infection significantly increase the risk of injury to major vessels and nerves. Excision of the entire tract is of paramount importance because recurrence and infection are common with an incomplete excision. With a complete excision, the recurrence rate in most series is less than 7%.
First Branchial Cleft Fistulae.
A first branchial cleft fistula generally requires an extensive procedure due to its proximity to the parotid gland and facial nerve. The procedure is carried out with a general anesthetic. The patient is positioned supine with a transverse roll beneath the shoulders and the head turned slightly away from the side of the lesion. The incision should be carried from an ellipse around the external opening up over the mandible and in front of the ear, in order to expose the superficial lobe of the parotid and the nerve (Fig. 15-5A). A nerve stimulator is useful in identifying the facial nerve. The fistula tract can then be safely dissected away from the nerve (Fig. 15-5B). The tract is suture ligated and divided at its connection with the external auditory canal (Fig. 15-5C).
Exposure of a first branchial cleft fistula. A. The fistula has been circumscribed with an elliptical incision carried superiorly just anterior to the ear. The superficial lobe of the parotid is identified. B. The superficial lobe of the parotid gland is reflected medially to expose the branches of the facial nerve and the fistula tract. C. The fistula is ligated as it enters the cartilage of the external auditory canal.
Second Branchial Cleft Sinuses or Fistulae.
Excision of a second branchial cleft sinus or fistula is the most common operation performed in this group of branchial lesions. The procedure is carried out with a general anesthetic, and the patient is positioned as described for a first cleft fistula excision. When a skin opening is present, some surgeons place a fine lacrimal duct probe to help facilitate dissection; this is a delicate maneuver, however, requiring care to avoid puncturing the tract wall. A transverse elliptical incision, in a skin crease if possible, is made around the external opening (Fig. 15-6A). If a cyst is present with no opening, a transverse incision is made. Sharp dissection of the tract and cyst, if present, is performed with fine scissors. To avoid injury to surrounding structures, the dissection remains right on the wall of the tract. After dissection is initiated, the course of the fistula can be determined by placing it on gentle traction and palpating more superiorly in the neck. In most cases, a transverse counter incision is made 3 to 4 cm above the first to safely and completely excise the tract (Fig. 15-6B). The dissection is carried deeper in the neck via the second incision up to the tonsillar fossa, where the tract is ligated with an absorbable suture and divided (Fig. 15-6B, inset). The incisions are irrigated with saline and suctioned dry. The platysma, subcutaneous tissue, and skin are closed in layers with absorbable sutures.
A. Anatomy of the neck in relation to a second branchial cleft fistula. B. The fistula opening is circumscribed by an incision. The tract is carefully dissected away from surrounding neck structures by staying on the fistula wall. The tract courses cephalad between the external and internal carotid arteries. A counter incision (dotted line) may be required to complete the dissection. C. The tract is ligated as it enters the pharynx (inset) and the incisions are closed in layers with absorbable sutures.
Third and Fourth Branchial Cleft Anomalies.
The principles of excision of third and fourth branchial cleft anomalies are the same as those for first and second branchial cleft anomalies.
Complications and Recurrence
Morbidity is caused by injury to the nerves and vessels near the tract at the time of surgery, whereas recurrence is caused by incomplete excision. The likelihood of these complications increases when inflammation occurs adjacent to the anomaly prior to or at the time of surgical excision. In the absence of infection, recurrence is rare. However, when infection precedes excision, recurrence exceeds 20%. In light of these facts, excision is indicated at diagnosis. Although rare, squamous cell carcinoma has been reported with branchial cleft cysts, this complication does not appear until adulthood.
Pyriform Sinuses and Cysts
Pyriform sinus lesions are rare lesions of the branchial apparatus and, as mentioned earlier, are thought to be third or fourth branchial derivatives. They usually appear as an abscess or mass in the left neck, specifically the thyroid lobe, and commonly communicate with the left pyriform sinus; as such, they may have an air–fluid level. In infants, a cyst may be asymptomatic or cause respiratory distress. Children may have a history of repeated upper respiratory infections and sore throats, as well as tenderness of the thyroid, with or without suppuration. Like other branchial anomalies, pyriform sinuses and cysts are often infected at presentation. Acute suppurative thyroiditis as a result of an internal fistula is the most common presentation. The diagnosis is based on the finding of left lower neck pain and swelling, demonstrated by a barium swallow (Fig. 15-7A) or endoscopy of the pyriform sinus fistula, or findings at surgery. When active infection and inflammation are present, a barium swallow may fail to show a tract. Once the inflammation subsides, however, the tract can be readily demonstrated. Complete excision is necessary to prevent a recurrence, and anatomy requires excision of the involved portion of left thyroid lobe in the process of tracing the fistula to the pyriform sinus (Fig. 15-7B). During dissection of the pyriform sinus cyst via a transverse neck incision, placement of an endoscope or a guidewire into the pyriform sinus has been found to be helpful in delineating the extent of the cyst.
A. Contrast study demonstrating a left pyriform sinus tract (arrow). B. At operation, the pyriform sinus tract involves an abscessed left lobe of the thyroid. The sinus tract has a metal flexible probe inserted into the tract. A left thyroid lobectomy encompassing the sinus tract was required.
The thymus arises as a pair of primordia from the third branchial pouch. The paired glands normally descend from the pharynx and fuse as they reach the aortic arch during the eighth week of gestation. The development of a congenital thymic cyst is thought to be due to persistence of the thymopharyngeal duct, which normally is obliterated.
Cervical thymic cysts are extremely rare, with less than 100 cases reported in the literature. They usually arise as solitary, unilateral neck masses and are clinically difficult to distinguish from branchial cleft cysts or macrocystic lymphatic malformations. Excision is performed by sharp dissection, with a transverse skin crease incision over the cyst. The cystic mass is typically found adjacent to the carotid sheath. In some cases, the cyst extends into the mediastinum, requiring splitting of the upper sternum. The pathologic finding of the thymic tissue in the cyst wall confirms the diagnosis. Because of the common embryonic origin of the thymus and parathyroid, parathyroid tissue is frequently found within thymic cysts.
Cervical clefts are a rare anomaly of newborns found in the midline of the neck. They appear as raw, protuberant, vertical strips of tissue that often contain skin tags, sinuses, and cartilaginous remnants (Fig. 15-8). These lesions are attributed to abnormal midline fusion of branchial arch pairs during the third and fourth weeks of gestation. Excision is indicated mainly for cosmesis, and therefore is usually delayed for several months. The cleft is excised via a series of Z-plasty incisions to prevent skin contractures that would form following a simple vertical elliptical incision.
Unrepaired midline cleft in an infant.
Thyroglossal duct cysts are one of the most common lesions in the midline of the neck. Although they are embryonic in origin, they rarely manifest in neonates. They are more commonly seen in preschool-aged children (25%) and in children up to 10 years old (40%). Frequently, however, these lesions are not identified until after the age of 20 (33%).
First described by Vater in 1723, the thyroglossal duct became known as the canal of His following studies by His in 1885 and 1891. In 1893, Schlange proposed that in addition to cyst resection, resection of the middle of the hyoid bone was also important. A manuscript authored by Sistrunk and published in the Annals of Surgery in 1920 earned him the distinction of being the first to fully understand surgical anatomy. Sistrunk was the first to realize that the duct traverses the hyoid bone up to the foramen cecum. He maintained that complete surgical excision of a thyroglossal duct cyst requires that the central portion of the hyoid bone and the duct, up to the base of the tongue, had to be resected in continuity with the cyst. This has remained the basic principle of the operation, which is known as the Sistrunk procedure.
Thyroglossal duct cysts are ectodermal remnants that may produce midline masses along the line of descent of the thyroid gland in the neck, from the base of the tongue to the pyramidal lobe of the thyroid gland. The embryogenesis of the thyroglossal duct is intimately associated with that of the thyroid gland, the hyoid bone, and the tongue. During the fourth to seventh weeks of gestation, the foramen cecum is the site of the development of the thyroid diverticulum; this structure arises caudal to the central tuberculum impar, which is one of the pharyngeal buds that leads to the formation of the tongue. As the tongue develops, the thyroid diverticulum descends into the neck, maintaining its connection to the foramen cecum. Simultaneously, the hyoid bone develops from the second branchial arch, and the thyroid gland develops and descends into its pretracheal position in the neck. As a result of these simultaneously occurring events, the thyroglossal duct may pass in front of, behind, or through the hyoid bone. Normally, the duct involutes and is resorbed once the thyroid gland completes its descent in the anterior neck.
Because the embryologic thyroglossal tract never reaches the surface of the neck, thyroglossal duct cysts never have a primary external opening. Secretion by epithelium-lined remnants of the duct can, however, lead to thyroglossal duct cyst formation anywhere along the course of the thyroglossal tract in the neck if the duct does not disappear. The stimulus for secretion by these remnants can occur at any time, thus accounting for the delayed appearance of these cysts in older children, adolescents, and adults.
Errors in thyroid descent or persistence of the thyroglossal duct can lead to the formation of lingual or other ectopic thyroid tissue, a pyramidal thyroid lobe, or a thyroglossal duct cyst. Complete failure of descent of the thyroid gland results in a lingual thyroid, which develops at the base of the tongue. In such instances, there is no thyroid tissue in the neck. Ectopic thyroid tissue within the thyroglossal duct remnant is reported in 20% to 45% of cases. Thyroid function studies are, however, not required unless there is concern about hypo- or hyperthyroidism. If a significant amount of thyroid tissue is removed at the time of the operation, a postoperative radionuclide scan should be obtained to make certain that sufficient residual thyroid tissue remains. Furthermore, for patients with large lingual thyroid gland and no normal thyroid tissue in the neck, clinical treatment should begin with the administration of thyroid hormone to decrease the size of the mass.
Clinical Presentation and Evaluation
Thyroglossal cysts are typically found in the anterior midline of the neck at or immediately adjacent to the hyoid bone but may occasionally be suprasternal (7%) or sublingual (3%). They are characteristically smooth, soft, and nontender, and are generally apparent on physical examination. Because of the attachment of the thyroglossal duct cyst to the hyoid bone, a typically positioned mass moves with swallowing. Nevertheless, this condition can be difficult to evaluate in young children and may also occur with other lesions located near the hyoid bone. If the diagnosis is not apparent on physical examination because of atypical features or location of the mass, inflammation, or additional neck pathology, studies such as ultrasonography, computed tomography, and magnetic resonance imaging can be invaluable in differentiating possible lesions. The differential diagnosis includes ectopic thyroid tissue, thyroid neoplasm, dermoid cyst, sebaceous cyst, lipoma, and submental lymphadenitis. Owing to communication with the base of the tongue at the foramen cecum, thyroglossal cysts commonly become infected, and patients may report infection as the first manifestation. This infection may spontaneously drain or require surgical incision and drainage prior to excision.
A thyroglossal duct cyst is treated by complete excision of the cyst and its tract up to the base of the tongue and including the central portion of the hyoid bone (Sistrunk procedure). This technique has reduced the incidence of recurrence to less than 10% from the 25% recurrence rate for cystectomy alone. An operation should be performed as early as possible to avoid the morbidity of intervening infection. If infection does occur, a course of antibiotics should be administered and the operation deferred until the inflammatory process is fully resolved. In some cases, incision and drainage are indicated prior to cyst resection. Complete surgical excision during active infection is inadvisable because of both the difficulty of the operation when infection is present and the risk of injury to the surrounding structures, which results in a higher incidence of recurrence.
Although papillary adenocarcinoma in thyroglossal duct specimens is not seen in children, it is reported in up to 10% of patients undergoing the Sistrunk procedure in adulthood. This observation lends further support to the cited rationale for early and complete excision.
The operation is performed with a general anesthetic with the patient in a supine position and the neck extended (Fig. 15-9A-F). A 3- to 4-cm transverse curvilinear incision is marked in a skin crease overlying the cyst and taken down through the platysma muscle. The cyst is usually found just beneath this layer. Dissection of the cyst and the thyroglossal duct follows the principle of Sistrunk, removing the midportion of the hyoid bone and the duct up to the base of the tongue. The cyst is dissected mostly by sharp dissection. Care is taken to avoid rupturing it during the procedure. When previous infection has occurred, a somewhat wider resection may be required to remove all portions of the cyst distorted by the inflammatory process. On dissection, a short duct is usually found in a cephaloposterior position. It is then traced to the area of the hyoid bone.
A. Anterior neck anatomy and a thyroglossal duct cyst extending through the hyoid bone. Lateral view and anterior frontal view (inset). The incision is represented by the dotted line. B. The platysma has been opened and the cyst dissected free, exposing the hyoid and deep anterior cervical muscles. The dotted line marks the area that will be incised with electrocautery. C. The hyoid bone is transected on both sides of the thyroglossal duct. D. The thyroglossal duct is then dissected to the foramen caecum. E. The appearance of a typical midline thyroglossal duct cyst in an 8-year-old male. F. At operation, the cyst and the resected central hyoid bone as well as the remaining tract attached to the base of the tongue can be readily seen. G. Pushing the base of the tongue anteriorly with a finger placed in the mouth of the patient facilitates visualization, dissection, and ligation of the tract. H. Once the thyroglossal duct cyst has been removed, the platysma, subcutaneous tissue, and skin are closed in layers using absorbable sutures.
The hyoid bone is transected on either side of the duct, leaving a 1- to 1.5-cm defect in the hyoid (Fig. 15-9D). When the cyst is suprasternal, a counterincision overlying the hyoid bone may be necessary. The strap muscles firmly attached to the hyoid are easily dissected with electrocautery. The duct is identified on the undersurface of the hyoid and is dissected up to the base of the tongue, where it is ligated with an absorbable suture and divided. It is sometimes helpful to place a finger at the base of the tongue, pushing ventrally to facilitate ligation of the duct at the foramen cecum (Fig. 15-9G and H). If necessary, bleeding from the cut surfaces of the hyoid is controlled with bone wax. No attempt is made to approximate the hyoid in the midline. Following an extensive dissection, a drain is occasionally necessary. The incision is closed in layers with absorbable sutures.
Complications and Recurrence
An uncommon but potentially dangerous postoperative complication is wound hemorrhage with resultant airway compression. Avoiding this situation requires careful hemostasis rather than routine drainage. Because of anatomic distortion or variability in neck anatomy, mistaking thyroid cartilage for the hyoid bone has been reported; this may result in severe injuries to the larynx. Wound infections are infrequent and respond to antibiotic therapy.
The recurrence rate following the primary resection of a previously uninfected thyroglossal duct cyst is 5%, and recurrence generally happens within 1 year of the procedure. It is usually attributed to incomplete excision of part of the cyst or its tract but can, however, be caused by distortion of the tissues due to inflammation or inadequate resection of the hyoid bone or the central stalk leading to the foramen cecum. Additionally, the presence of multiple tracts or rupture of the cyst at the time of excision can lead to recurrent disease.
Recurrence typically manifests with infection in the upper neck. A course of antibiotics is administered until the inflammation has resolved, and a second operation is then performed through the same incision. Reexcision of persistent cysts is associated with recurrence rates as high as 25% to 35%.
Preauricular Sinuses, Pits, and Cysts
Although preauricular sinuses, pits, and cysts are sometimes classified with first branchial cleft anomalies, they are not of true branchial cleft origin. Rather, they represent ectodermal inclusions related to aberrant development of the auditory tubercles. Sinuses and pits are thought to occur when the ectoderm is enfolded during the development and merging of the 6 hillocks of the ear. The sinuses are often short and end blindly. They occasionally connect internally to the external auditory canal. The sinus tracts extend from the skin through the subcutaneous tissue close to the superficial temporal artery and characteristically terminate in the cartilage of the external auditory canal.
Preauricular anomalies are much more common than first branchial cleft anomalies, with an incidence ranging from 15.5 to 43.7 per 10,000 births in various populations. These anomalies more commonly appear in people of Asian and African-American descent and are slightly more common in females than in males (3:2). Preauricular sinuses may be associated with other congenital anomalies such as deafness. They also have an increased incidence of concomitant renal anomalies (eg, branchio-oto-renal [BOR] syndrome).
Preauricular sinuses can be either inherited or sporadic. When inherited, these lesions show an incomplete autosomal dominant pattern with reduced penetrance and variable expression. The appearance of bilateral preauricular sinuses is associated with an increased likelihood of being inherited.
Most preauricular cysts are bilateral. When unilateral, they more commonly arise on the right side. These anomalies are commonly observed at birth, and are typically located superior to the tragus of the ear in the cymba conchae and subcutaneous tissue superficial to the parotid fascia (Fig. 15-10). The tract of sinuses and cysts is lined with stratified squamous epithelium.
Most sinuses and cysts are asymptomatic; however, parents often report sebum intermittently draining from the sinuses. The sinuses extend down to the temporalis fascia and may be juxtaposed to the perichondrium of the helix. Occasionally, these patients develop infections that result in an abscess. In this setting, a thorough examination will reveal a preauricular lesion as opposed to a first branchial anomaly.
Excision is recommended for lesions that form a palpable mass or drain sebaceous material because they are the most likely to become infected (Fig. 15-11). Complete surgical excision of the subcutaneous cyst and sinus tract down to the level including the cartilage of the external auditory canal is the treatment of choice for the uninfected draining sinus. Care should be taken to avoid rupture of the sinus and to perform a complete excision. If infection is present, excision should be delayed because it makes dissection more difficult and increases the risk of incomplete excision and hence recurrence. Infection, which is most commonly staphylococcal, should be treated with antibiotics and warm soaks to encourage drainage and control surrounding inflammation. In some patients, needle aspiration or incision and drainage is required to control the infection. Once the infection is completely resolved, definitive excision is performed. When the cyst or sinus has only simple single tract involvement, recurrence is uncommon. By contrast, when the sinus has multiple branches, recurrence is as high as 42%. Because postoperative wound infection is common, all patients should undergo a course of antibiotics.
Operative technique used to excise a preauricular sinus or skin tag. An elliptical incision is placed around the sinus and dissection of the skin and a block of subcutaneous tissue is carried to the temporalis muscle fascia or to the perichondrium of the helix.
Preauricular skin tags (Fig. 15-12) are common embryological remnants that may include cartilage and are located just medial to the external ear canal. These lesions reflect minor incomplete or aberrant migration of the ear anlage. Most children with these lesions are otherwise normal, and surgical excision is performed primarily because of aesthetic concerns (Fig. 15-11). Children with preauricular tags that occur in conjunction with other more complex ear malformations frequently have significant hearing impairment.
Photograph of a preauricular skin tag with a cartilaginous component at its base.
Dermoid and Epidermoid Cysts
Dermoid cysts are derived from ectodermal elements that were either buried beneath the skin and superficial muscles (eg, the platysma and orbicularis oculi) or failed to separate from the neural tube. They form along the lines of embryonic fusion in the anterior neck and are differentiated from superficial epidermoid cysts histologically by the accessory glandular structures they possess, including sebaceous glands, hair follicles, connective tissues, and papillae. Both dermoid and epidermoid cysts contain sebaceous material within the cyst cavity.
Dermoid and epidermoid cysts are generally unilocular and are seen at birth. They gradually expand with age because of secretions from the entrapped glands and the accumulation of epithelial material.
The lining of a dermoid cyst is thicker than that of an epidermoid cyst and may contain dystrophic calcification. The lipid material in dermoids is from the sebaceous glands. This material resembles the texture of cheese and contains cholesterol crystals in addition to glandular secretions.
The dermoid cavity is lined with a thick stratified squamous keratinized epithelium surrounded by dermal appendages such as hair follicles and sebaceous, eccrine, and apocrine glands.
Dermoid cysts are most commonly found along the supraorbital palpebral ridge, and commonly appear as a swelling in the corner of the eyebrow (Fig. 15-13). Although they are attached to the underlying bony periosteum, they are usually minimally mobile and nontender. In this setting, most patients do not require preoperative imaging. However, when lesions on other parts of the face or skull are immobile, patients should undergo a skull radiograph to assess whether there is bony defect in the skull (Fig. 15-14). Midline dermoid cysts of the skull, including the nasal bridge, may occasionally penetrate the calvarium, forming a dumbbell-shaped mass with dermoid elements on either side of the bone (Fig. 15-15). Patients with midline lesions should undergo a computed tomography scan or a magnetic resonance imaging scan to ensure that there is no intracranial extension.
Right lateral eyebrow soft tissue nodule. This is the classic location for an angular dermoid cyst.
Skull radiograph depicting a cranial bone defect beneath a scalp soft-tissue nodule.
A midline nasal bridge dermoid cyst that is connected to an intracranial component through the cribriform plate.
Dermoid cysts can also be found in the midline of the neck overlying the hyoid bone and, as such, are frequently confused with midline thyroglossal duct cysts (Fig. 15-16). They are, however, more superficial and lack connections to the hyoid bone and the tongue. Any midline scalp lesion suspected of being a dermoid cyst should undergo preoperative evaluation with magnetic resonance imaging to rule out intracranial extension. Expanding lesions can erode into adjacent bone; however, this rarely occurs. Malignant degeneration of dermoids is also possible but exceedingly rare.
Diagram of the typical locations for dermoid cysts of the head and neck: the extended angular dermoid, the internal angular (nasal bridge) dermoid, and the midline neck dermoid.
Complete surgical excision is the treatment of choice for all dermoid and epidermoid cysts; this confirms the diagnosis, prevents infection, and ensures aesthetic outcomes. If dermoid cysts are seen during the neonatal period, the operation can be postponed until the child is 6 to 12 months old. Complete removal of the capsule is of utmost importance in decreasing the risk of recurrence. Aspirating or opening these cysts may result in spillage of cyst contents, which in turn may lead to infection or recurrence.
Excision should be performed with a general anesthetic and with meticulous technique. Attention should be paid to the important nerves such as the branches of the facial nerves supplying the forehead and the supraorbital nerves. Injury to the supraorbital branches of facial nerve can be avoided if the incision is made at the hairline of the eyebrow with minimal lateral and medial dissection, staying on the cyst wall. The cyst is usually deep into the muscles and may be adherent to the periosteum. When there is neurapraxia or stretching of the superior branch of the facial nerve, there may be a postoperative inability to elevate the eyebrow. This inability diminishes over several months. Transection or the use of electrocautery can, however, result in permanent injury to the nerves.
Rarely, the cyst may extend into the orbit. In this setting, care should be taken not to injure the eye and the surrounding muscles and nerves. A midline cyst should be approached with caution, and preparations made for a possible craniotomy.