Chiasmal gliomas: appearance and long-term changes demonstrated by computerized tomography.

A survey of 22 cases showed the broad spectrum of lesions collectively termed "chiasmal gliomas." Three computerized tomography (CT) patterns were diagnostic: a tubular thickening of the optic nerve and chiasm, a suprasellar tumor with contiguous optic nerve expansion, and a suprasellar tumor with optic tract involvement. Globular suprasellar tumors lacking these features required a histological examination for diagnosis. Tumor growth was documented by CT in only three chiasmal gliomas; all were the globular type. Failing visual function did not reflect chiasmal tumor growth, and stable vision did not exclude it. Both patients with tubular optic nerve thickening and two of three patients with unilateral optic nerve expansion had neurofibromatosis. Five tumors became smaller after irradiation. Complications of radiation therapy included calcification of lenticular nuclei and remote infarcts. In patients who underwent biopsy, the CT appearance did not differentiate juvenile pilocytic astrocytoma from anaplastic astrocytoma. Thus, CT guides the diagnosis and neurosurgical treatment of chiasmal gliomas, establishing the need for biopsy or ventricular shunting.