Branchial anomaly Branchial sinus 2010-07-27T10:10:03Z UMLS:C0266624 HP:0100272 Branchial cleft sinus SNOMEDCT_US:253259008 A congenital branchial sinus is a remnant of the embryonic branchial arches and their intervening clefts and pouches that has failed to regress completely. Sinuses typically have their external orifice inferior to the ramus of the mandible. They may traverse the parotid gland, and run in close vicinity to the facial nerve in the external auditory canal. Branchial sinuses have to be distinguished from the preauricular cysts and sinuses, which are ectodermal remnants from an aberrant development of the auditory tubercles, tend to be bilateral, and are localized anterior to the tragus of the ear.