Second branchial cleft anomaly

Second branchial cleft anomaly (also known as second branchial cleft cyst, sinus, or fistula) is a congenital malformation arising from incomplete obliteration of the second branchial cleft (also called the second pharyngeal cleft) during embryonic development. These anomalies are the most common type of branchial cleft malformation, accounting for approximately 90-95% of all branchial anomalies. They primarily affect the head and neck region and may present as a cyst (a closed, fluid-filled sac), a sinus (a blind-ending tract opening to the skin surface), or a fistula (a complete tract connecting the skin surface to the pharynx, typically opening internally at the tonsillar fossa). Clinically, second branchial cleft anomalies typically present as a painless, smooth, fluctuant mass along the anterior border of the sternocleidomastoid muscle in the lateral neck, most commonly in the upper to middle third. A sinus or fistula may present as a small opening on the skin of the lower lateral neck from which mucoid fluid may drain. These anomalies are present from birth but may not become clinically apparent until childhood or even adulthood, often following an upper respiratory tract infection that causes the lesion to enlarge or become infected. When infected, the mass becomes tender, erythematous, and swollen, and may form an abscess. Treatment is primarily surgical, with complete surgical excision being the standard of care to prevent recurrent infections and potential complications. Surgery is ideally performed when the lesion is not actively infected. If infection is present, initial management includes antibiotics and, if necessary, incision and drainage, followed by definitive surgical excision once the acute inflammation has resolved. Recurrence rates after complete excision are low but increase if the anomaly has been previously infected or incompletely removed. There is no medical therapy that can resolve these anomalies without surgery.

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