Parotid fistula – an extra-orally draining infected dentigerous cyst associated with a supernumerary fourth molar in ascending ramus

Abstract

An infected cyst, associated with a supernumerary fourth molar in the ascending ramus of the mandible, presented with parotid swelling, trismus and pain. It was managed as a parotid infection but recurred and a draining pre-auricular sinus developed, which was thought to be a parotid fistula. This was managed by cautery, followed by excision of the fistula, both of which were unsuccessful. Following this, further investigations revealed that the cause of the facial sinus was in fact a cyst associated with a mandibular fourth molar in the posterior ascending ramus. The tooth was extracted, via a pre-auricular extra-oral approach, under general anaesthetic. This case shows how a dental panoramic radiograph can be extremely helpful at ruling out certain pathology. It also demonstrates how the symptoms of an infection arising from a tooth in the ramus may be misdiagnosed as salivary gland pathology.