First branchial arch abnormality: diagnostic dilemma and excision with facial nerve preservation.

Objective: To report a case of first branchial arch abnormality and the problems associated with misdiagnosis. A succinct literature review is included.

Setting: Teaching hospital in Scotland.

Methods: A 10-year-old girl presented with localised erythema and swelling in the left parotid region. This was treated with antibiotics and incision and drainage. She re-presented four years later with a history of recurrent discharge. A first branchial arch abnormality was suspected and a magnetic resonance imaging scan arranged.

Results: Imaging showed a fluid-filled sinus tract originating adjacent to the anterior wall of the cartilaginous left external auditory canal. The sinus tract was seen to extend anteriorly and inferiorly through the superficial lobe of the left parotid, and to open onto the left cheek lateral to the left masseter. The tract was explored and excised under general anaesthesia, via two separate incisions, with preservation of the facial nerve.

Conclusion: The diagnosis of a first branchial arch abnormality is generally based on a high index of clinical suspicion, when a neck swelling is noted in a child. Magnetic resonance imaging is a useful modality for investigation, and helps to delineate the position of the tract and its relationship to the facial nerve.