Cholesterol cysts of the temporal bone: diagnosis and treatment. Cholesterol cyst (or granuloma) of the temporal bone, a recognized clinical entity distinct from cholesteatoma, is more common than previously thought. Apparently it is caused by obstruction of previously pneumatized temporal bone air cells. Surgical cure is achieved by drainage and reestablishment of normal pneumatization. This paper reviews 14 cholesterol cysts of the temporal bone, emphasizing the importance of preoperative imaging and surgical approach. Use of magnetic resonance imaging differentiates cholesterol cysts from cholesteatoma or other neoplasms. Computed tomography delineates the location of the lesion and defines temporal bone anatomy essential to surgical approach. The two studies together allow the surgeon to properly plan drainage, as in the case of a cholesterol cyst, versus excision or exteriorization, as in the case of cholesteatoma. The infralabyrinthine approach to a petrous apex cholesterol cyst is the procedure of choice when hearing preservation is desired. 