Figure 101-1. CT or MRI of second branchial cleft cysts.
These lesions often present with infection, and it is best to minimize inflammation and infection with antibiotics prior to excision, making the dissection and identification of important structures easier. Abscesses can be treated with minimal intervention, such as needle aspiration or if needed, incision and drainage. During the procedure, it is important to communicate with anesthesia to avoid paralysis for proper nerve monitoring. Radiologic imaging with CT or MRI can be helpful (Fig. 101-1). Rates of recurrence for branchial cleft cysts is quoted around 3%, but this increases to 20% in cases that have undergone a prior attempt at excision.9
Anatomy and Embryology
The branchial arches form during the fourth to eighth week of gestation as four pairs of well-developed ridges with associated clefts. Each has a cartilaginous center (mesoderm), a cleft (ectoderm), an internal pouch (endoderm), and a nerve (Table 101-1). These structures mature into the major structures of the head and neck (Fig. 101-2).
Table 101-1 Pharyngeal Arch Structures
Figure 101-2. Derivation of various areas of the head and neck from the branchial arches and clefts of the embryo.
First branchial cleft anomalies, which comprise 8% of branchial cleft anomalies, are divided into type 1 and type 2.10 Type 1 branchial cysts often present as a fistula around the conchal cartilage. The tract can follow the course of the external auditory canal and is lined by squamous epithelium.11 Type 2 branchial lesions are found near the angle of the mandible and are composed of both epithelium and mesoderm (as opposed to only epithelial elements in type 1). Both type 1 and type 2 first branchial cleft anomalies can be closely associated with the facial nerve, although type 2 lesions are more likely to be intimately involved with the nerve. Type 2 branchial lesions can loop under the facial nerve, pushing it laterally and inferiorly.12 The tract for a first branchial cleft usually extends from the opening near the mandible, near the posterior aspect of the parotid, and toward the external auditory canal. One should monitor the facial nerve at all times, with visualization of the face during the entire excision and avoidance of paralysis with anesthesia.
The most common branchial anomaly is derived from the second branchial cleft groove, representing 90% of branchial cleft anomalies.13 It can occur as an isolated cyst or as a sinus tract/fistula that extends from the cervical skin to the tonsillar fossa. The cysts will often present at the time of an upper respiratory tract infection as an enlarging, tender mass. If a fistula is present, it will course through the internal and external carotid arteries, over the hypoglossal and glossopharyngeal nerves to end in the tonsillar fossa. A cyst can occur anywhere along this tract, but most commonly occurs in the anterior triangle of the neck below the hyoid.
Third and fourth branchial cleft lesions are rare. Third branchial cleft cysts present low and anterior in the neck. Fistulas can course from the piriform fossa and drain to the anterior cervical skin. This tract pierces the thyrohyoid membrane and tracks under the glossopharyngeal nerve and internal carotid artery, but stays above the vagus nerve. These lesions can be intimately involved with the thyroid, and sometimes a hemithyroidectomy is required for repeated recurrences. An infected TGDC or third branchial cleft cyst may be the cause of suppurative thyroiditis in children.14 The external location for a fourth branchial cleft is the same as the second and third, but the internal opening is near the apex of the piriform sinus. Fourth arch masses are extremely rare and but reports do exist. Third and fourth branchial sinus/tract dissections are similar to a second branchial cleft. Endoscopy at the beginning of the case can greatly assist in locating and resecting the tract. One promising surgical option for third or fourth sinus tracts is cauterization or sclerotherapy.15
The standard treatment for all types of branchial anomalies is complete surgical excision. The surgery is performed under general anesthesia and the patient is positioned with the neck slightly extended with a shoulder roll. If there is a sinus tract or fistula present, a small ellipse is made around this opening after it has been cannulated with a small lacrimal probe. A probe can be used or some use a small injection of methylene blue, although this can be messy. The tract is then dissected cephalad until the end of the sinus tract or until the internal opening of the fistula is reached. The dissection for the most common branchial cleft anomaly, the second branchial cleft, penetrates the platysma, rises along the carotid sheath and turns medially near the branches of the internal carotid artery and courses between the posterior belly of the digastric muscle and stylohyoid muscle, and over the hypoglossal nerve before ending near or in the tonsillar fossa. The tract is then ligated with absorbable suture. Often a direct laryngoscopy or simply a finger placed in the oropharynx can help to visualize the course of the tract and assist with dissection. Some patients might require a “stepladder” incision to trace the tract superiorly (Fig. 101-3).
Cartilaginous remnants are normally small and present in the subcutaneous tissue along the anterior border of the sternocleidomastoid, are usually palpable and easily resected. These rarely get infected and removal is for cosmetic indications.
Preauricular cysts, pits, and sinuses are common in children and are thought to develop from the first two branchial arches. They are more common and more often bilateral in comparison to first branchial cleft cysts and rarely become infected. The tracts extend from the skin down to the helical cartilage of the auricle and are lined with squamous epithelium. Treatment is surgical excision and the recurrence rate ranges from 19% to 40%.16
Figure 101-3. Picture of sinus tract.
Figure 101-4. Locations of thyroglossal duct cysts.
Thyroglossal Duct Cysts
TGDCs are congenital lesions that develop from the thyroglossal duct tract that occurs during the descent of the thyroid. The thyroid descends from the foramen cecum at the sixth week of gestation and tracts along the anterior neck in close association with the developing hyoid bone. This tract usually involutes, but if it persists the tract can present as a TGDC at any point from the foramen cecum to the thyroid (Fig. 101-4). TGDCs are the most common neck mass besides benign lymphadenopathy in the pediatric population.17 Physical presentation reveals a midline neck mass that may move with protrusion of the tongue (Fig. 101-5). US is useful to look at the characteristics of the cyst, but is most important to determine if there is a normal thyroid gland present. In rare cases, the TGDC could be the sole functioning thyroid tissue in the patient.
Figure 101-5. Thyroglossal duct cyst.
Treatment is surgical excision and removing the entire tract with a core of tissue and the central portion of the hyoid bone can minimize recurrence. Rarely, papillary thyroid carcinoma can be found in the specimen.18 The procedure is performed under general anesthesia with the neck extended and placement of a shoulder roll. A horizontal skin incision is made over the cyst, with no need to excise skin unless a fistulous tract or infection has involved the dermis. Careful dissection around the cyst then allows continued dissection superiorly toward the hyoid bone. Muscular attachments to the central hyoid bone are removed with cautery and the hyoid is removed en bloc with the cyst and tract. A core of tissue is then removed above the hyoid bone toward the base of tongue. The tract is then ligated with absorbable suture. Placing a gloved finger at the base of tongue can sometimes facilitate this maneuver. The wound should then be irrigated copiously and closed in a layered fashion. A drain is often used. Complete excision is considered curative and TGDCs have a recurrence rate of less than 10% when using this method.17
Other midline lesions to keep in the differential include dermoid and epidermoid cysts, lymph nodes, thymic cysts, and bronchogenic cysts.
Dermoid cysts should be considered in the differential of any midline lesion, although they can be off midline as well. On examination, dermoid cysts present as firm masses that are soft, mobile, nontender, and grow slowly. Dermoid cysts contain tissue from the three germinal layers, which can include sweat glands and sebaceous glands. Treatment is total surgical excision. If a nasal dermoid occurs, it can penetrate the bone and a CT or MRI should be performed to rule out intracranial extension. Midline dermoid cysts are likely entrapped epithelium at the time of embryonic fusion.19
Lesions of the thymus usually occur in the lower neck, but can present anywhere from the piriform sinus to the chest. The differential includes thymic cysts, thymic hyperplasia, or thymoma.
The most common cause of a neck mass in the pediatric population is benign cervical adenopathy. Cervical lymph nodes are palpable in 40% of infants and 55% of pediatric patients on examination.20,21 Lymph nodes that are less than 1 cm in size and asymptomatic are considered normal in children less than 12 years of age.14 Lymphadenitis is most commonly seen in the submandibular region and cervical nodes, and the source of infection can be viral, bacterial, fungal, or neoplastic. Bacterial and viral infections causing upper respiratory infections are the most common cause of cervical lymphadenopathy. Other possible sources of cervical LAD include fungal (in immunocompromised patients), cat scratch disease, mononucleosis, atypical mycobacterium, and tuberculosis. As mentioned previously, lymphomas or metastatic disease can also present with nodal enlargement in the neck. Although rare, one should also consider Kawasaki disease, sarcoidosis, Rosai–Dorfman syndrome, and histiocytosis X.
Acute suppurative lymphadenitis is most common in the 6-month to 3-year range, with lymph node enlargement associated with an upper respiratory tract infection. The most common etiologies include Staphylococcus aureus and group A beta-hemolytic streptococci. There is commonly overlying skin changes with erythema and cellulitis, with an associated leukocytosis and fever. The lymph node enlarges and eventually outgrows the blood supply, resulting in central necrosis. Management can sometimes include needle aspiration of purulence, but often requires an incision and drainage with placement of a drain or packing under anesthesia. An incision is made in the area of fluctuance and blunt dissection should break up all loculations. It is important to place the incision in a place that minimizes risk to vital structures, such as the facial nerve, and allows for the best cosmesis. Antibiotics are geared toward Staphylococcus and Streptococcus but cultures should be taken with a change in antibiotic therapy if necessary. The induration from the abscess can take several weeks to resolve, but recurrence is rare. If the abscess recurs, it should prompt investigation of a possible underlying anomaly. Viral infections rarely cause suppurative adenitis.
Lymphadenitis can also be chronic or subacute with enlargement of lymph nodes not associated with an acute infection, although sometimes can occur in a patient with recurrent URIs, tonsillitis, otitis media, or allergic rhinitis. Often the lymph node is solitary, nontender, and mobile. Excisional biopsies are recommended generally when the lymph node is larger than 2 cm and has been present for longer than 8 weeks, or has concerning characteristics such as immobility or rapid growth. Once excised, it is important to obtain cultures, histopathology, and flow cytometry.
Mycobacterial infections, usually caused by the atypical mycobacterium Mycobacterium avium-intracellulare-scrofulaceum (MAIS) complex, can be very challenging to manage. The pathogens are usually acquired through the mucous membranes during the eruption of teeth, not through person-to-person transmission. These lesions often cause discoloration of the skin and can fistulize over time (Fig. 101-6). Antibiotic therapy is not always curative. It most commonly occurs in children 1 to 5 years of age and often has associated asymptomatic lymphadenopathy but no fever or leukocytosis. The response to antibiotic therapy can be disheartening with little improvement and sometimes surgery is required to excise the infection. Adjuvant treatment with clarithromycin or rifabutin is often indicated, as is a consultation with the infectious disease team. In contrast, children with M. tuberculosis usually have fever and respiratory symptoms along with positive findings on chest x-ray and the purified protein derivative skin test.
Cat scratch disease, caused by Bartonella henselae, can cause tender cervical lymph node enlargement in 25% of cases. Usually there is a history of contact with a cat within 2 weeks of the development of tender lymphadenopathy. The site of inoculation is usually an extremity. The diagnosis can be made using B. henselae-based serologic indirect fluorescent antibody test or enzyme immunoassays. The disease is usually self-limited with resolution in 2 to 8 weeks and no antibiotic therapy is necessary; however, rarely patients can suffer disseminated disease.22
Figure 101-6. Atypical mycobacterium infection.