Idiopathic inflammatory perioptic neuritis simulating optic nerve sheath meningioma.

Between 1976 and 1982, we examined 13 patients with clinical and radiographic findings consistent with optic nerve sheath meningioma. All patients had visual loss, evidence of optic nerve dysfunction, centrocecal visual field defects, and echographic and computed tomographic evidence of optic nerve or sheath enlargement. All underwent surgery for biopsy or excision of their presumed tumors. However, adequate histologic sampling of all lesions failed to demonstrate meningioma in four patients; two of these four showed inflammatory infiltration of the dural sheath, whereas the other two showed only edematous or dense fibrous tissue. There was no evidence of other systemic disease in any of these cases. We conclude that optic nerve or sheath enlargement, probably induced by an idiopathic inflammatory perioptic neuritis, may simulate a sheath meningioma. Proper diagnosis requires biopsy confirmation.