Intracranial Dermoid Cyst Ruptured into the Membranous Labyrinth Causing Sudden Sensorineural Hearing Loss: CT and MR Imaging Findings

SUMMARY: A ruptured dermoid cyst is rare and can present with various symptoms. We report imaging findings of an intracranial dermoid cyst that ruptured into the endolymphatic sac, causing sudden sensorineural hearing loss. ABBREVIATIONS: S sigmoid sinus Dermoid cyst is a rare congenital intracranial tumor.1 Itarises from ectopic inclusion of the embryonic ectoderm into the neural tube during the third to fifth weeks of embry-onic life and is usually located in the midline.2 Dermoid cysts are composed of a stratified squamous epithelium and skin adnexal structures, such as hair follicles, sebaceous, or sweat glands; therefore, they contain products of these adnexal structures and epithelium, such as lipid metabolites, choles-terol crystals, hair, decomposed epithelial cells, and calcifica-tion.2,3 Radiologic diagnosis of dermoid cysts is made on the basis of lipid content.1,4 Symptoms related to unruptured der-moid cysts are nonspecific.1,3,5,6 A dermoid cyst can ruptur