First Branchial Cleft Anomaly

First branchial cleft anomaly is a congenital cyst, sinus or fistula from failure of closure of the first branchial cleft, lying near the external ear canal, parotid gland and angle of the mandible. It risks recurrent infection and facial nerve injury at surgery.

It accounts for about 1% to 8% of branchial anomalies. Work type I is a duplication of the membranous external ear canal lying anterior and inferior to the ear, parallel to the canal, and type II involves ectoderm and mesoderm, with a tract passing from the ear canal to the upper neck through or near the parotid gland and facial nerve. It presents in children and young adults, and is often mistaken for an abscess.

Pathophysiology.

Incomplete obliteration of the dorsal end of the first branchial groove leaves epithelial lined tracts. Secretions are trapped and infection recurs.

Swelling or recurrent abscess near the angle of the jaw, parotid or in front of the ear, a pit or sinus opening in the neck under the jaw (type II), discharge from the ear canal, and recurrent parotid area infection. Facial nerve palsy may follow repeated surgery or infection.

Red flags.

• Rapidly enlarging swelling with fever.
• Facial weakness.
• Failure of repeated incision and drainage.

Diagnosis is clinical and by imaging. Ultrasound shows a cyst. Magnetic resonance imaging or CT with contrast defines the tract and its relation to the parotid, the facial nerve and the ear canal. Fistulography is occasionally used. Audiometry is done. Culture the pus.

Differential diagnosis.

• Preauricular sinus.
• Parotid abscess or cyst.
• Lymphadenitis.
• Second branchial cleft cyst.
• Atypical mycobacterial infection.
• Lymphatic malformation.

Treat acute infection with antibiotics and drain the abscess if needed; avoid incision where possible as it complicates later surgery. Definitive treatment is complete excision of the cyst and tract after inflammation settles (usually 4 to 6 weeks), with facial nerve identification and, for type II, superficial parotidectomy.

• Co-amoxiclav (amoxicillin 500 mg with clavulanic acid 125 mg): 1 tablet orally three times daily for 7 days; maximum 1.5 g amoxicillin daily (1 g three times daily for severe infection, maximum 3 g); monitor liver tests, diarrhoea and rash; give 1 tablet twice daily when creatinine clearance is 10 to 30 mL/min; children 25 mg/kg amoxicillin twice daily.
• Clindamycin (penicillin allergy): 300 to 450 mg orally four times daily for 7 days; maximum 1.8 g daily; monitor for diarrhoea and Clostridioides difficile infection; children 3 to 6 mg/kg four times daily.

Monitoring. Facial nerve function after surgery, wound review at 1 to 2 weeks, and recurrence review at 6 and 12 months.

Referral and escalation. ENT, head and neck, or paediatric surgery experienced in parotid surgery.

Special groups. Children need weight based dosing and facial nerve monitoring in surgery.