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Fourth branchial cleft and pouch anomalies are rare but clinically important entities that require a high index of suspicion. A missed diagnosis can prolong patient morbidity resulting in incorrect treatment and probable recurrence. These anomalies are secondary to errors in embryogenesis from incomplete involution of the fourth branchial cleft or pouch, resulting in the formation of a cyst, sinus, or fistula. They commonly present as a recurrent lateral neck swelling in the pediatric population. Surgery is the mainstay of treatment.
They commonly present as an infected neck swelling in childhood that can easily be mistaken for suppurative lymphadenitis. Otolaryngologists must be vigilant, as errors in diagnosis can lead to increased patient morbidity and unproductive interventions.
As is the case with all congenital anomalies, knowledge of embryology is key to understanding the pathogenesis, presentation, and treatment of the resultant condition. By the fourth week of gestation the 6 arches, clefts, and pouches making up the branchial apparatus have formed. The fourth branchial arch is responsible for the formation of many important cervical structures, including the superior laryngeal nerve and the pharyngeal constrictors.
The fourth branchial pouch gives rise to the superior parathyroid glands bilaterally as well as the ultimobranchial body, which itself is in part responsible for the development of parafollicular C-cells in the thyroid gland.
Bearing this in mind, fourth branchial anomalies characteristically present in close association with the thyroid gland, with a tract ascending to the pyriform sinus. Consequently, consideration must be taken to address the full extent of the tract, often including the thyroid gland.
Anatomy
Fourth branchial anomalies are diagnosed by their anatomical course. They are classically described to begin in the apex of the pyriform sinus, pierce the larynx near the cricothyroid ligament, and then pass between the superior and recurrent laryngeal nerves.
Right and left anomalies differ in their course beyond this point. A left sided anomaly descends in the tracheoesophageal groove, loops around the aorta in a posterior to anterior direction, ascends posterior to the common carotid before passing over the hypoglossal nerve (cranial nerve [CN] XII), and exiting the neck anterior to the sternocleidomastoid muscle (SCM). A right-sided anomaly also descends in the tracheoesophageal groove to the level of the subclavian artery where it loops around in a posterior to anterior direction before ascending with the common carotid artery and following the same course as on the left side.
The relationship of the tract to the piriform apex, cricothyroid joint, and superior laryngeal nerve are the main points of differentiation between a third and fourth branchial anomaly; a third branchial anomaly passes cephalad to the superior laryngeal nerve whereas a fourth passes caudally (Figure 1).
Although they mainly contain stratified squamous epithelium or respiratory ciliated epithelium, the presence of ectopic tissue(s) can aid in the diagnosis of a branchial anomaly, but cannot help distinguish a fourth from a third anomaly.
Presentation varies based on the age of the patient. Neonates with fourth branchial anomalies are likely to experience respiratory distress, whereas older children tend to present with either a lateral neck abscess or suppurative thyroiditis.
A range of symptoms has been described, including upper respiratory tract infection, cervical pain, thyroid tenderness, cellulitis, hoarseness, and odynophagia.
Pediatric case of the day. Infected fourth branchial pouch sinus with an extensive complicating cervical and mediastinal abscess and left-sided empyema.
Physical examination must include a thorough head and neck examination, including flexible laryngoscopy. Typical neck findings including lateral neck swelling, tenderness, overlying erythema, warmth, induration, and possible fluctuance. Respiratory symptoms are possible and flexible laryngoscopy may reveal unilateral supraglottic swelling, erythema, purulent debris, or all of these if there is a connection to the piriform sinus. The combination of unilateral neck swelling and supraglottic findings should raise a high index of suspicion for a third or fourth branchial anomaly. Laboratory tests are of limited use in this setting. Radiological investigations of use include ultrasound, contrast swallow studies, magnetic resonance imaging, and computed tomography. Timing of investigative studies is also important. Magnetic resonance imaging and computed tomography are most useful during acute infection. Although the actual sinus or fistula tract typically cannot be easily seen on imaging, the combination of an infected neck cyst with adjacent thyroid inflammation and inflammation of the tissues along the expected course of the tract is pathognomonic. Direct laryngoscopy and contrast swallow studies have the best positive predictive values of all investigative tests, with values of 90% and 88%, respectively.
Contrast swallow studies can be helpful in illustrating fourth branchial anomalies after the acute infection has subsided, as contrast can pool in the pyriform fossa sinus and proximal tract. Direct laryngoscopy can be performed during an acute infection, and if a sinus tract is identified it confirms the diagnosis.
Definitive treatment for fourth branchial anomalies is surgical. Open and endoscopic approaches have both been described. Endoscopic intervention is used either as an initial intervention or as an adjunct to open excision.
In the setting of infection, aggressive treatment with antibiotics should be the initial management strategy with a planned definitive resection performed several weeks later.
Antibiotic choice should be dictated by culture and sensitivity testing, if available. Typical organisms found are oral flora susceptible to penicillin or related β-lactamase–resistant antibiotics.
If sepsis, respiratory compromise, or progression of the infection is present, needle aspiration or incision and drainage can be considered, but it may complicate future definitive resection.
In an open transcervical surgical resection, both proximal and distal ends of the lesion are addressed in an effort to avoid recurrence. This is technically challenging, as the anatomical course of fourth branchial anomalies can be quite circuitous. Distal lesion excision usually involves removal of the cystic mass as well as the ipsilateral thyroid gland, as the fistula tends to be either immediately medial, lateral, or through the gland itself.
If there is preoperative concern that the tract extends into the mediastinum, then a preoperative general or cardiothoracic surgery consult can be considered. Risks of the open procedure include nerve injury and the potential for significant bleeding. Neuromonitoring can be considered as an adjunct to guard against injury to the recurrent laryngeal nerve. Long-acting paralytics should be avoided to allow for intraoperative nerve stimulation, if necessary. To prevent postoperative infection, perioperative antibiotics should be used to protect against skin flora 1 hour before incision.
Endoscopic cauterization of the sinus tract in the piriform is the emerging method of choice.
This can be used in conjunction with transcervical approach or as a stand-alone therapy. Studies have shown equivocal recurrence rates between open procedures and endoscopic cauterization, with significantly reduced morbidity associated with the endoscopic technique.
Both open and endoscopic approaches should begin with a detailed examination of the upper airway to identify pyriform sinus fistulae. The patient should be prepped and draped in standard fashion for suspension laryngoscopy. This should be performed with an appropriately sized laryngoscope for the patients’ size and age. A shoulder roll can be placed for gentle neck extension. A tooth guard is placed over the patient’s maxillary dentition to avoid dental injury. Anesthetic selection is at the discretion of the surgeon and anesthesiologist, but the procedure can be performed with the patient spontaneously ventilating or with a small endotracheal tube. Care should be taken to thoroughly examine the hypopharynx with either a microscope or telescope to aid with visualization. If a fistula or sinus tract is identified, obliteration should be strongly considered. This has been described using laser, chemical irritants, and electrocautery.
In our practice, the Bugbee electrocautery has been successful and straightforward for usage (Figure 2, Figure 3). The Bugbee electrocautery tip is placed within the lumen of the piriform sinus tract and low-wattage electrocautery is used to circumferentially cauterize the tract mucosa until it blanches white. High wattage should be avoided as this can cause thermal injury to the adjacent recurrent laryngeal nerve, though this is often temporary. No antibiotics are necessary.
Figure 2Pyriform sinus fistula tract. (Color version of figure is available online.)
The transcervical approach is appropriate for patients who have failed pyriform sinus obliteration or have opted for an open approach. The patient’s bed should be rotated 180° from the anesthetist to allow intraoperative laryngoscopy if necessary.
The patient should be positioned on the operating room table in the supine position in neck extension, similar to a neck dissection. The neck is then prepped in a sterile fashion. A horizontal incision is planned over the observed swelling that includes the anterior border of the SCM. The relaxed skin tension lines should be followed, using neck creases when possible. Skin fistula should be incorporated into the incision using an appropriate ellipse. If this proves impractical, a series of stair-step incisions should be planned to limit the length of the primary incision (Figure 4, Figure 5). In the case of a large cyst or planned partial thyroidectomy, or both, an incision at the level of the cyst with extension toward the midline is appropriate.
Figure 4Options for neck incisions: (A) standard incision, (B) extended approach required, and (C) stair-step incision.
To address a fistula tract, if present, the skin should be incised via the planned elliptical incision, which includes the tract’s skin opening. Subcutaneous tissue and platysma should be divided taking care not to transect the tract. To aid in identification of the tract, lacrimal probes can be inserted via the skin into the tract (Figure 5) or methylene blue can be injected. The tract should be followed superiorly and bluntly dissected free from the adjacent tissue circumferentially. Traveling superiorly, the limit of traction on the skin may be reached and an additional incision may be necessary to continue (Figure 6).
Figure 6Intraoperative view of tract excision extending toward cyst superiorly.
If a cyst is present, the planned incision over the cyst should divide the dermis, subcutaneous tissues and platysma. Subplatysmal flaps are raised superiorly and inferiorly and held in place with fish hooks, lone star retractors, or an assistant. The anterior border of SCM is identified and retracted posteriorly. The cyst should then be visible. Using a combination of blunt and sharp dissection the cyst should be carefully dissected. Great care should be taken not to rupture cyst contents or disrupt a tract. The spinal accessory nerve (CN XI) is found posterolateral to the cyst. Caution should exercised when dissecting on the surface of the lesion as mass effect may displace the nerve in any direction. The nerve should be identified and traced superiorly and inferiorly to avoid injury. The lesion may also be near the carotid sheath. Careful dissection is required to extricate the cyst from these structures. Deep to the cyst lies CN XII, which should be identified and left intact (Figure 7).
Figure 7Cyst exposure and proximity to hypoglossal nerve.
Care should be taken to identify the fistulous tract as it connects to the cyst. It may be necessary to alternate between incisions until the tract is completely identified and can be delivered into the main operative site.
If there has been a history of suppurative thyroiditis or the tract is noted to run through the thyroid itself, a hemithyroidectomy as well as a partial resection of the ipsilateral posterior thyroid ala should be considered (Figure 8). Care is taken to not injure the underlying recurrent laryngeal nerve in the standard fashion for a hemithyroidectomy. The removal of the thyroid cartilage allows access to the pyriform sinus, marking the superior extent of the tract. This area can be excised and mucosal defect repaired. A suction drain should be placed into the wound bed.
Figure 8Surgical excision requiring hemithyoidectomy and limited removal thyroid ala.
Patients should be admitted overnight for monitoring. Drain removal should be considered when the surgeon’s criteria are met. Regardless of approach, patients can be started on a diet on postoperative day 1. If there is concern for a fistula, the patient should be placed on nil per os status with consideration for wound re-exploration. Once the drain is removed and patients are tolerating per os well they can be safely discharged home.
Complications
The potential complications of open neck exploration for fourth branchial anomalies can be significant. As previously highlighted, these lesions course near several delicate structures, such as the recurrent laryngeal, spinal accessory, and hypoglossal nerves. It has been noted that complications are more prevalent in cases performed during an acute infection and in patients younger than 8 years.
Consideration should be taken to postpone definitive neck exploration until after this age when possible. Complications with endoscopic intervention are greatly reduced compared to open excision.
Recurrence is the most common complication of both endoscopic and transcervical approaches, but this can be minimized with adherence to strict technique.
Fourth branchial anomalies are rare but they must be considered in cases of congenital lateral neck masses in the pediatric population, particularly with thyroid involvement. By understanding the basics of branchial apparatus embryology, the pathogenesis, presentation, treatment, and complications of these anomalies become predictable. Presenting symptoms can depend on age. Surgical excision is the mainstay of curative treatment. Open neck exploration is the traditional approach; however, paradigms are shifting toward endoscopic treatment as the primary modality.
Disclosure
The authors reported no proprietary or commercial interest in any product mentioned or concept discussed in this article.
Pediatric case of the day. Infected fourth branchial pouch sinus with an extensive complicating cervical and mediastinal abscess and left-sided empyema.
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