Epidermoids are slow-growing, benign (non-cancerous) cysts that are typically congenital (present at birth). They result from skin cells that are misplaced during embryogenesis and left behind while the nervous system is developing. Epidermoids can be found in the petrous apex, a pyramid shaped portion of the temporal bone located 3-4 centimeters deep to the middle ear. While epidermoids are present at birth, symptoms are generally not experienced until adulthood because the cyst is too small at first to produce any symptoms. As the epidermoid grows, it may erode the petrous apex bone and invade the inner ear, facial nerve, petrous carotid artery, vestibulocochlear nerve, trigeminal nerve and the brain itself. Hearing loss, dizziness, facial weakness, retro-orbital headaches and sensory abnormalities of the face are early symptoms. Meningitis may occur if the epidermoid ruptures.<\/p>\n\n\n\n
Diagnostic workup for petrous apex lesion includes a comprehensive audiogram (hearing test) and high resolution imaging studies, including both CT and MRI scans. Surgery is the only treatment for symptomatic epidermoids, but it is often not possible to remove all of the epidermoid tissue during surgery. Therefore, continued monitoring with serial CT\/MRI scans as well as repeat surgery for recurrent symptoms may be recommended.<\/p>\n\n\n\n