Unusual presentation of a first branchial arch fistula with maxillofacial infection: a case report

BACKGROUND: First branchial cleft anomaly (FBCA) is a rare congenital defect that arises due to incomplete closure of the ventral portion of the first and second branchial arches. There are variable complex clinical manifestations for patients with FBCA, which are prone to misdiagnosis and inadequate treatment. FBCAs usually involve the facial nerve with a consequent increased risk of facial nerve damage. Here, we present an unusual case of FBCA presenting with two preauricular pits in association with an abnormal maxillofacial cyst. CASE PRESENTATION: A 10-month-old girl presented to our department due to recurrent maxillofacial infections accompanied by swelling or abscess of the left cheek and purulent discharge from the preauricular pit for 4 months. A 3D-computed tomography (CT) fistulogram and magnetic resonance imaging (MRI) revealed two conjunctive tract lesions: one tract arose from the skin surface anteroinferior to the external auditory canal (EAC), through the deep lobe of the left parotid, and anteriorly extended to the left masseter; the other extended from the superficial lobe of the left parotid to the intertragic notch. After the maxillofacial infection was controlled by intravenous antibiotic administration, surgery was performed. Intraoperative tools, such as facial nerve monitors, microscopes, and methylene blue dyes, were used to facilitate the complete dissection and protection of the facial nerve. On follow-up over one year, the patient recovered well without facial palsy or recurrence. CONCLUSION: FBCA with maxillofacial cysts is rare and prone to misdiagnosis. Physicians should pay attention to this anatomic variant of FBCA with the fistula track located deep inside the facial nerve and projected medially to the masseter.