Intracranial intraparenchymal and intraventricular schwannomas: report of 18 cases.

Intracranial schwannomas of the brain, which are unrelated to the cranial nerves, are extremely rare. In this article, we present a series of eighteen cases of intracranial intraparenchymal and intraventricular schwannomas, which is the largest series to date.During the 10-year period from January 2000 to October 2010, we encountered 2491 histologically established cases of intracranial schwannomas, of which only 18 were not related to the cranial nerves. Clinical profiles, radiological features, surgical procedures, intraoperative findings and outcomes were extracted from the patient records and neuroimaging data.No patients were preoperatively diagnosed with schwannoma. The diagnosis of schwannoma was made by pathological examination with H&E staining and immunohistochemical examination. The 18 cases with intracranial ectopic schwannomas account for 0.8% of all the intracranial schwannomas that were observed within the same time period at our hospital. The age distribution of the patients ranged from 7 to 78 years. There was a slight male predominance: 11 male and 7 female patients (M:F=1.6:1). Headaches were the most common presenting symptom and were found in most cases. Common neuroradiological characteristics included peritumoral edema and intralesional cysts.Intracranial intraparenchymal and intraventricular schwannomas are rare, benign neoplasms that cannot be preoperatively differentiated from other parenchymal tumors. Surgical excision is curative, and the long-term prognosis is good. Additional studies are needed to confirm the histogenesis of this schwannoma type.