Dermoid cysts of the head and neck are rare congenital benign tumors. According to the literature they represent about seven percent of all dermoids and less than one percent of all intracranial neoplasms. Extradural dermoid cysts are very rare. We report a case of intracranial extradural dermoid cyst of mastoid bone. We believe that this is the second documented extradural dermoid cyst, the first case reported in the literature (Ammirati et al., 2007) was in close relation to the petrous apex but ours is in close relation to mastoid antrum. Hearing loss was the only clinical presentation in this case, while neurological symptoms were the main presenting symptoms in the first reported case. We present our management of this rare case with respect to the clinical, radiological, histopathological, and surgical aspects and conclude that dermoid tumors, though rare, need to be included in differential diagnosis of middle ear lesions. 1. Introduction Dermoid tumors are not true neoplasms but are inclusion cysts composed of ectodermal elements. They are uncommon lesions, accounting for approximately 0.3% of all brain tumors and about seven percent of all dermoids of the head and neck . Dermoid cysts are derived from both the ectodermal and mesodermal elements. A keratinizing squamous epithelium is typically present along with dermal derivatives including hair follicles, smooth muscle, and apocrine and sebaceous glands. Fibroadipose tissue is also present. The exact etiology of these neoplasms is unknown though the most likely theories are incomplete closure at lines of fusion or traumatic implantation of skin elements . We report a case of intracranial extradural dermoid cyst of mastoid bone, with respect to the clinical, radiological, histopathological, and surgical aspects. 2. Case Report An 18-years-old girl diagnosed at the age of three years to have right otitis media with effusion (OME) was treated medically. She presented again at the age of 8 years with the same complaint but did not respond to the medical treatment and underwent right myringotomy with ventilation tube and adenoidectomy. Two years later, her symptoms recurred and underwent right T-tube insertion. Symptoms had recurred again after removal of the T-tube 2 years later. She presented at the age of 18 years with right hearing loss and intermittent nonpulsatile tinnitus. There was no history of otorrhoea, otalgia, or vertigo, and there were no abnormal neurological signs or symptoms. Physical examination revealed retracted right tympanic membrane, while the left was normal. Audiogram
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