Epidermoid cysts and cholesterol granulomas centered on the posterior fossa: twenty years of diagnosis and management.
The clinical features, diagnosis, and management of 23 posterior fossa epidermoid cysts and 9 petrous apex lesions presenting to one unit over a period of 20 years are summarized. Of the epidermoid cysts, 13 were entirely infratentorial, but the other 10 had an additional supratentorial component. Presenting symptoms and signs were usually long-standing and at onset had often been vague and nonspecific. With time, however, a variety of neurological deficits that depended on the site of the lesion developed. These were generally combinations of cerebellopontine (CP) angle and jugular foramen syndromes, deafness, facial palsy, and motor weakness. Diagnostic procedures have changed greatly over the review period. Computed tomography and magnetic resonance imaging have replaced air encephalography and contrast ventriculography. The better preoperative localization of these lesions allows rational planning of the surgical approach required for optimal tumor exposure, which is essential for any attempt at total excision, considering the large size of the majority of these tumors when diagnosed. We favor operation through a posterior fossa craniectomy for those tumors restricted to the CP angle or 4th ventricle, but routinely use a combined supra- and infratentorial approach if the lesion has a more rostral component. The infiltrating nature of epidermoid cysts within the cranium compromises the extent of excision if neurological deficit is not to be increased, but we attempt as complete an excision of tumor and capsule as possible in the hope that many years will pass before symptoms recur. Cholesterol granulomas seem to respond well to simple cavity drainage and have shown no tendency to recur.