Third branchial cleft anomaly

Third branchial cleft anomaly (also known as third branchial arch anomaly, third pharyngeal cleft cyst, or third branchial pouch sinus) is a rare congenital malformation arising from the incomplete obliteration of the third branchial cleft (pharyngeal cleft) during embryonic development. Branchial cleft anomalies account for approximately 17% of pediatric cervical masses, and third branchial cleft anomalies represent only 2–8% of all branchial anomalies, making them quite uncommon. These anomalies can present as cysts, sinuses, or fistulae located in the lower lateral neck, typically on the left side. The internal opening of a third branchial fistula or sinus tract characteristically courses from the piriform sinus (in the hypopharynx), passes posterior to the common carotid artery, and may extend through or near the thyrohyoid membrane to the skin of the lower anterior neck. Clinically, patients may present with a painless lateral neck mass, recurrent neck abscesses, or recurrent episodes of suppurative thyroiditis (infection of the thyroid gland), which is a hallmark feature particularly suggestive of a third or fourth branchial pouch anomaly. Symptoms often become apparent in childhood, though some cases may not be diagnosed until adulthood. Recurrent infections in the lower neck or thyroid region, drainage from a cervical sinus tract, dysphagia, or hoarseness may also occur. Diagnosis is supported by imaging studies such as ultrasound, CT scan, or MRI, and may be confirmed by direct laryngoscopy demonstrating an opening in the piriform sinus, or by barium swallow studies. Treatment is primarily surgical. Complete surgical excision of the cyst, sinus, or fistula tract is the definitive treatment and is recommended to prevent recurrent infections. Acute infections are typically managed with antibiotics and, if necessary, incision and drainage prior to definitive surgery. Endoscopic cauterization or obliteration of the internal opening in the piriform sinus has emerged as a less invasive alternative in select cases. Prognosis after complete excision is generally excellent, with low recurrence rates when the entire tract is removed.

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