Epidermoidomas of the cerebellopontine angle and temporal bone: CT and MR aspects.

Epidermoidomas were found in four locations within and adjacent to the temporal bone: cerebellopontine angle, petrous apex, facial geniculate ganglion region, and tympanic-mastoid cavity. Lesions in each of these locations presented different clinical and imaging characteristics. Cerebellopontine angle epidermoidomas were seen on computed tomography (CT) as low-attenuation masses in the posterior fossa. Petrous apex and geniculate ganglion region lesions destroyed and expanded the bone of their respective regions. Tympanic-mastoid cavity epidermoidomas were relatively nonspecific, soft-tissue masses. CT study of the brain and temporal bone was the single most informative imaging procedure in the preoperative evaluation of these lesions. Magnetic resonance images complemented CT scans for evaluation of the size and extent of the abnormality but were relatively nonspecific and did not allow preoperative differentiation of epidermoidomas from other temporal bone lesions.