Optic nerve sheath meningioma: visual improvement during radiation treatment.

PURPOSE To describe four patients with optic nerve sheath meningioma in whom visual improvement began to occur even before completion of a standard course of radiation therapy. DESIGN Retrospective case review. METHODS A review was conducted of 35 patients who received stereotactic three-dimensional conformal radiotherapy for optic nerve sheath meningioma from 1990 to 2005. RESULTS Four patients with radiographic confirmation of optic nerve sheath meningioma were identified who had neuro-ophthalmologic assessment, which included perimetry, either while radiation treatment was underway or immediately afterwards. All of the patients showed improvement in visual acuity and visual fields. CONCLUSION A rapid response to radiation therapy may occur in some patients with optic nerve sheath meningioma. In such patients, it may be possible to customize the radiation dose by assessing of visual function during the course of therapy.