Cystic pilocytic astrocytomas of the cerebral hemispheres. Surgical experience with 51 cases and long-term results.

This study concerns 51 cases of cystic pilocytic astrocytoma of the cerebral hemispheres. At operation these tumors closely resembled cerebellar astrocytomas, presenting as a big cyst contiguous with the lateral ventricle and containing a small mural nodule. The nodule was in a deep location in 26 cases, and always showed marked contrast enhancement on computerized tomography scans. The most frequent presenting symptom was epilepsy (68%), and the most common sign was papilledema (85%). The major goal of surgery was extirpation of the nodule. The follow-up period of the 34 cases available for long-term review ranged from 6 to 31 years (mean 17 years). Of these, 28 patients (82%) had a good outcome; four (12%) had a fair result, and two (6%) had a poor response. An analysis of these results shows that total extirpation of the mural tumor was associated with the best outcome, whether or not the cyst wall was completely removed. Radiation therapy was irrelevant to the prognosis for these patients. On the other hand, partial excision of the nodule, correlated with the deep location of the tumor, was the cause of the two poor results in this series and resulted in multiple operations for recurrences in two other patients. Nevertheless, two of these patients are still alive and well many years after incomplete surgical treatment. On the basis of this study, the importance of recognizing the occurrence of this "benign" tumor of the cerebral hemispheres is stressed, and the hypothesis of a common origin from subependymal glia of all pilocytic astrocytomas is supported.