First Branchial Cleft Fistula Piercing through the Main Trunk of the Facial Nerve.

First branchial cleft fistulas are congenital malformations that result from the incomplete closure of the ectodermal portion of the first branchial cleft. These fistulas typically appear as small pits or subcutaneous masses in the upper neck and cheek and can cause pain due to infection and inflammation. Surgical excision is the most effective treatment, but special attention is necessary to avoid facial nerve injury due to the proximity of the lesion to the nerve and variations in their arrangement. Here, we report the successful treatment of a first branchial cleft fistula piercing through the main trunk of the facial nerve in a 3-year-old girl. Intraoperative findings revealed that the fistula in the parotid gland opened into the cheek area from the ear canal. Identification of the facial nerve trunk was challenging due to the malformation of the lower end of the auricular cartilage, which is an anatomical landmark of the facial nerve. The trunk of the facial nerve was divided proximally by the fistula and merged just past the fistula. Preoperative magnetic resonance is important for determining the fistula location, surrounding anatomical variations, and fistula-facial nerve arrangement. Furthermore, early surgical treatment should be considered to prevent tissue scarring and adhesion due to infection, which can lead to facial nerve injury.