The Sesquialter (First and a Halfth) Branchial Cleft Anomaly.

A 6-month-old presented with a sinus in the neck coursing from below the body of the mandible, between the carotid and parotid spaces, and terminating posterior to the stylomastoid foramen on MRI. Facial nerve monitoring was used, a lacrimal probe was placed in the sinus, an elliptical incision was made in the skin, and the tract was followed to the parapharyngeal space. Pathology demonstrated a keratinous squamous epithelial lining, skin adnexae, and elastic cartilage. Because there were clinical, radiographic, and pathological features intermediate to first and second branchial anomalies, we propose calling this a sesquialter (first and a halfth) branchial anomaly.