Teaching NeuroImages: Optic nerve sheath meningioma presenting as gaze-evoked amaurosis

A 47-year-old woman reported a slowly progressive 15-month history of intermittent visual loss on rightward gaze as well as diminished visual acuity of her right eye. Examination revealed right ocular red desaturation, afferent pupillary defect, impaired visual acuity, and optic disc swelling (figure, A). Head imaging revealed an optic nerve sheath meningioma (figure, B and C). A brain MRI performed 4 months prior to the current evaluation displayed a similar pattern of optic nerve enhancement. Gaze-evoked amaurosis is transient monocular visual loss on eccentric gaze. It is suggestive of intraconal pathology and is putatively caused by position-dependent occlusion of the retinal or optic nerve circulation.1 The most common causes of gaze-evoked amaurosis are optic nerve sheath meningioma and cavernous hemangioma.1 Treatment options for optic nerve sheath meningioma include observation, radiotherapy, radiosurgery, and resection.2