Optic nerve sheath meningiomas.

Meningiomas are benign neoplastic lesions arising from meningothelial cells of the meninges. Primary orbital meningiomas, originating in the optic nerve sheath, represent 1-2% of all meningiomas, and are the second most common optic nerve tumor after gliomas. They primarily affect middle-aged adults. Patients typically present with visual loss, frequently associated with optic atrophy and often with optociliary shunt vessels. The lesion is usually unilateral, but is bilateral in about 5% of cases. Meningiomas show characteristic indolent growth over years, progressing inexorably to blindness in the affected eye. Management should be conservative in most cases. In very rare situations, surgery has improved visual prognosis. In most patients, however, surgery offers no benefit, and should be reserved for those with blindness or severe proptosis, or when extension toward the optic canal is documented. Although preliminary results of radiotherapy are encouraging, very few patients have been treated using this modality, and the long-term advantage for vision remains unproven. Even when untreated, the prognosis for life is excellent, with an overall tumor-related mortality of 0%.