Abstract

Optic nerve gliomas manifest either as a solitary form or a component of von Recklinghausen's neurofibromatosis. The reported incidence of coexistence with neurofibromatosis varies from 12% to 70%. Usually there are no significant cytological differences between the gliomas that accomapny the disease and those that are deemed to be solitary manifestations. The only possible difference between them is the apparently more common association, with the former, of extensive arachnoid hyperplasia and of a more florid local gliomatous infiltration into the leptomeninges, altogether resulting in perineural thickening. Our cases were 8 and 6 years old girls, respectively, presented with slowly progressive proptosis for 4 years and visual disturbance for 2.5 months. There were multiple cafe au lait spots on their trunks, and case 2 showed Lisch nodules in the iris. MRI of brain revealed unilateral optic nerve thickening with involvement of chiasm or multiple intracranial lesions. Resection of optic nerve tumor was performed. Microscopically, variable degree of tumorous change was seen. Most typically enlarged area was composed of intraneural and perineural portions surrounded by a layer of intact dura. Intraneural tumor revealed proliferation of elongated, spindle-shaped pilocytic astrocytes in intertrabecular spaces and distention of the pial septa with fibrovascular thickening. Another segment had areas with reactive gliosis. Perineural tissue was considerably thickened and, associated with proliferation of meningothelial cells and fibroblasts intermingled with astrocytes and Rosenthal fibers. There were increase of the optic nerve diameter and distention of the overlying dura. Foci of arachnoid cell hyperplasia were noted in both cases, although differed in degree. Immunohistochemically, the tumor cells expressed glial fibrillary acidic protein in intraneural and perineural portions particularly in case 2.

• Keywords: Optic nerve;Glioma;Neurofibromatosis;Perineural thickening