Intracranial parenchymal schwannoma. A clinicopathological and neuroimaging study of nine cases.

The clinical, radiological, and pathological features of nine cases of intracranial parenchymal schwannoma are described. The clinical course in four patients 23 years of age or younger mirrored the indolent nature of this neoplasm. Imaging studies included computerized tomography in eight patients and magnetic resonance imaging in three. The lesions were well demarcated with only mild surrounding edema. Five tumors were deep within the temporoparieto-occipital region, three were in the cerebellum, and one lay peripherally in the parietal lobe. Over two-thirds of the nine tumors were either cystic (five) or contained areas of cystic degeneration (two). One lesion was frankly hemorrhagic. A variety of imaging characteristics and contrast enhancement patterns were observed, including those of a cyst with a mural nodule and peripheral enhancement. Of the four solid neoplasms, two enhanced homogeneously while the other two demonstrated heterogeneous enhancement. Six tumors were resected totally. The follow-up period ranging from 2 months to 2 years has shown no recurrences. Microscopically, immunohistochemically, and ultrastructurally, the tumors were indistinguishable from peripheral schwannomas. A possible mechanism underlying the histogenesis of these rare lesions is discussed. The importance of recognizing this tumor is stressed, particularly in younger patients, given its benign nature, radiological resemblance to other tumors such as pilocytic astrocytoma, and favorable response to resection.