OPTIC-NERVE SHEATH MENINGIOMA MISTAKEN AS ANTERIOR ISCHEMIC OPTIC NEUROPATHY (AION)

Background The optic nerve sheath meningioma usually presents with a d iffuse atrophy of the disc and a diffuse depression of the visual fiel d. Applying this rule too rigidly can lead to a false diagnosis. Patie nt A 45y-old-woman presented with atrophy of the upper disc and a corr esponding altitudinal field defect in her right eye. AION was diagnose d. Seventeen years later the patient returned with an exophthalmus. Th e disc was atrophic and a shunt vessel connected the central retinal v ein with the choroid. CT revealed an orbital mass. The diagnosis of an optic nerve sheath meningioma was made and confirmed at surgery. Disc ussion The meningioma may have occluded an upper posterior ciliary art ery? mimiking an AION. Alternatively, the meningioma may have destroye d the fibers running through the upper half of the disc and caused swe lling of the remaining fibers in the lower half of the disc. Conclusio n In the combination of swelling and atrophy of one disc an optic nerv e sheath meningioma should be considered, even if the two components a re located in different sectors, In optic nerve sheath meningioma visi on decreases insidiously as opposed to the acute drop typical for ante rior ischemic optic atrophy.