Meningioma of the optic foramen as a cause of slowly progressive blindness; report of three cases.

Abstract

M ENINGIOMAS arising from within the orbital cavity make up only a very small segment of intracranial meningiomas. Primary intraorbital meningiomas have been removed surgically and verified pathologically in 17 cases at the Mayo Clinic. 1 Included in this group of intra-orbital meningiomas are those tumors that arise from the meninges within the confines of the optic foramen and that subsequently tend to extend both intra-orbitally and intracranially. These latter form an interesting subgroup in that, aside from their extreme rarity, they grow at an unusually slow rate and demonstrate a remarkable tendency toward bilaterality. The only symptom associated with the foraminal meningiomas is a slowly progressive blindness not accompanied by headache or pain. The first reported instance of the synchronous occurrence of meningeal tumors involving both optic nerves was that described by Schott 5 in 1877 as an incidental finding on postmortem examination in the case of a 55-yearold blind charwoman who died of hepatic cirrhosis. The tumors were the size of a bean and were intimately attached to the arachnoid sheath of each optic nerve. To our knowledge, the only other case of such bilateral tumors is that reported by Dandy 3 in 19~r The neoplasms were diagnosed clinically, and an intracranial operative procedure was used for the first time in the treatment of such lesions. Dandy particularly stressed the need for distinguishing these tumors from optic neuritis because he felt that unnecessary blindness could be prevented if the true situation were recognized sufficiently early. His case was that of a 13-year-old girl who had had progressive bilateral loss of vision for a period of 7 years. At operation he discovered collarlike growths that encircled the optic nerves and extended 0.75 cm. intracranially and 1.5 cm. intra-orbitally from their attachment at the point where the dura is reflected as it passes through the optic foramen. Dandy also reported the case of an 8-year-old boy who had noted bilateral loss of vision but in whom he found only a single neoplasm. These foraminal meningiomas should not be confused with the small tumors arising along the mesial part of the sphenoid ridge and producing visual symptoms secondarily as a result of their encroachment upon the optic nerve. 4 Meningiomas arising from within the optic foramen have been removed