A contribution to the natural history of optic nerve sheath meningiomas

Objective: To describe the natural history of patients with primary optic nerve sheath meningioma (ONSM) who were cared for without intervention. Methods: A retrospective review of the medical records of 42 patients identified in the database of an academic neuro-ophthalmology unit who had been diagnosed with a unilateral ONSM. Twenty-five had been referred after treatment had been implemented, and 1 was blind at referral. The remaining 16 patients who were followed up with observation only are the focus of this study. Results: The study subjects were followed up for a mean of 6.2 years (range, 2-18 years). The mean follow-up from the time of the first symptom was 10.2 years (range, 3-28 years). No patient died or incurred neurological deficits other than vision loss. At diagnosis, 12 of 16 had a visual acuity of 20/100 or better; 11 had a visual acuity of 20/30 or better. At follow-up, 8 of 16 had a visual acuity of 20/100 or better; 6 had a visual acuity of 20/30 or better. Three patients had slight improvement. Visual fields remained stable in 4 patients and improved in the 3 patients whose visual acuity also improved. Conclusions: Some patients with ONSM have a stable course for many years, and a few may even show slight improvement. The routine application of radiation therapy may unnecessarily expose some patients to complications and should be reserved for those patients whose visual function declines under observation.