Diagnostic modalities and natural behavior of optic nerve gliomas

The preoperative evaluation of a patient with a suspected optic nerve glioma has been enhanced by the use of recently developed techniques such as computerized tomography and ultrasonography, which enable evaluation of tumor configuration. Conventional radiographic studies with stereoscopic orbital foramen views, as well as tomography of the optic canal, are important and permit accurate measurement of canal size, shape, and margins. The glioma characteristically develops as an intradural, monolobular, fusiform enlargement of the orbital, canalicular, or chiasmal portion of the nerve. Enlargement may be produced by astrocytic proliferation within the nerve or within the perineural sheath, by arachnoid hyperplasia, intracellular mucosubstance production, or by vascular congestion. Each of these features will be described and discussed.