Meningiomas of the anterior visual system.

Meningiomas, whether primary in the orbit, optic canal or intracranial area, typically cause slowly progressive loss of vision covering months to years. They usually occur in white women of middle age. Tumors in the orbit or optic canal almost always affect vision unilaterally; intracranial tumors, while usually causing unilateral visual loss initially, eventually cause bilateral loss of vision, often with blindness in one eye. Depending upon the size and location of the tumor, the ocular signs and symptoms of meningiomas may include visual field abnormalities, optic atrophy, edema of the ipsilateral optic disc, papilledema, diplopia, and proptosis. The diagnosis of meningiomas in all locations has been greatly facilitated by recent advances in computer assisted tomography. However, tumors confined to the optic canal or its foramina are small when vision is first lost and therefore are still difficult to detect. Hypocycloidal polytomography may be useful; other neuroradiologic studies rarely are. Treatment is surgical. Based on a review of more than 3000 meningiomas reported in the literature, the frequency and characteristics of the signs and symptoms of meningiomas in each location are discussed, as are the anatomy, pathology, natural history, and probable mechanisms.