Pilocytic Astrocytoma Presenting as an Extra-axial Tumor in the Cerebellopontine Angle: Case Report

GLIAL TUMORS IN the cerebellopontine angle (CPA) are rare. Four histologically distinct types of glial tumors of the CPA have been described in the literature as ependymoma, medulloblastoma, mixed glial tumor, and fibrillary astrocytoma. This case report describes a pilocytic astrocytoma of the CPA. A 58-year-old man with a hearing loss had an extra-axial tumor in the left CPA that extended into the internal auditory canal. The characteristics of the tumor on magnetic resonance imaging scans differed from those of typical CPA tumors. It adhered avidly to the cochlear and vestibular nerves, which had to be sacrificed for gross total resection. Microscopic examination showed the typical features of an adult-type pilocytic astrocytoma. (Neurosurgery 37 :125-128, 1995)