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

Teaching hospital in Scotland.

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.

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.

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.

Abnormalities of the third branchial arch are less common than those of the second arch and usually present with left thyroid lobe inflammation. This paper describes 15 cases of pyriform sinus fistulae of third branchial arch origin usually presenting as recurrent thyroid abscess on the left side.

A retrospective review of 15 cases of third arch fistulae managed 2000 and 2008, diagnosed based on histopathology and radiological evidence of a fistulous tract, and treated with fistulectomy with left hemithyroidectomy.

All patients (six boys and nine girls, aged three to 15 years) presented with recurrent low neck inflammation. Pre-operative ultrasound, computed tomography fistulography and barium swallow demonstrated a third arch fistulous tract, left-sided in all cases. The fistula was detected intra-operatively and pathologically in all cases. Surgery (successful in all cases) emphasised complete recurrent laryngeal nerve and ipsilateral pyriform sinus exposure, to facilitate tract excision, with left hemithyroidectomy. There was no recurrence over three to five years' follow up.

Paediatric recurrent low neck inflammatory episodes, due to thyroidal abscess, especially left-sided, should raise suspicion of pyriform sinus fistulae.

We report an extremely rare case of a complete congenital third branchial arch fistula in a nine-year-old boy.

A case report and a review of the English literature concerning third branchial arch fistula of congenital origin are presented.

A nine-year-old boy presented with a history of a small opening in the middle third of the anterior neck since birth, with recurrent surrounding swelling. There was no history of surgical drainage or spontaneous rupture. Computed tomography with contrast injection into the external cervical opening revealed a patent tract from the neck skin to the base of the pyriform sinus. Complete excision of the tract up to the pyriform sinus with left hemithyroidectomy was performed. Follow up at 22 months showed no recurrence.

To our knowledge, this case represents a very rare occurrence of the congenital variety of complete third branchial arch fistula at an unusual site. This case indicates that third branchial arch fistula can be complete, and may present in the anterior neck, an unusual site. In such cases, computed tomography fistulography and injection of dye into the pyriform sinus enables intra-operative delineation of the tract.