Primary optic nerve sheath meningiomas: a follow-up study.

Objective: The management of optic nerve sheath meningiomas (ONSM) remains controversial, but includes surgery, radiotherapy and plain observation. We present a follow-up study and treatment modalities based on our classification system.

Patients and methods: A retrospective analysis was performed of 90 patients with optic nerve sheath meningiomas who were treated between 1991 and 2008 (n=65 surgery only, n=5 radiation only, n=18 surgery and postoperative radiation, n=2 observation). Follow-up data was available, ranging from 6 to 220 months with a median of 45.8 months.

Results: Our classification system differentiates between intraorbital (type 1), intracanalicular or intrafissural (type 2), and intraorbital and intracranial (type 3) ONSMs. Thirty-seven tumors demonstrated extension through the optic canal (type 2a). 41 further tumors reached the chiasm (type 3a) or contralateral side (type 3b). Visual acuity was not significantly influenced by surgery but did become worse with a longer duration of preoperative symptoms and a longer follow-up period. Radiotherapy improved vision in 4 and preserved vision in 16 out of 23 cases.

Conclusions: Loss of vision in optic nerve sheath meningiomas is a question of time. Radiotherapy should be offered for intraorbital ONSM. Surgery with decompression of the optic canal and intracranial tumor resection is still favored for tumors with intracanalicular and intracranial extension.