Primary Cyst in the Mastoid

A Case Report

Abstract

Formation of cysts in the paranasal sinuses is common but in the mastoid cavities, it is rare. A 49-year-old female had a primary cyst in a mastoid cavity. Operation confirmed that the aditus was completely obliterated by the cyst wall and a cholesterol granuloma. There was no communication between the mastoid cavity and the epitympanic cavity. The etiology of mastoid cysts has been uncertain, but obstruction of the air ventilation in the middle ear space at the aditus is thought to play an important role in the etiology. Mastoid cyst is diagnosed by aspiration of the cyst, but it is important to differentiate it from meningoencephalocele and meningocele protruding into the mastoid cavity. Radiologic imaging, especially CT and MRI, should be done before the aspiration.