Optic Nerve Sheath Meningiomas. The Evolving Role of Radiation Therapy and Anatomic Assessment with OCT

Introduction: Optic nerve sheath meningiomas are uncommon but not rare lesions. The advent of imaging study has dramatically increased the ability to diagnosis these lesions often before there is substantial visual loss. Radiation therapy introduced by Lawton Smith can reduce progression and in many cases improve optic nerve function. OCT is a recent advance in anatomic assessment appropriate to these lesions and their follow up.

Materials and Methods: A retrospective review of 31 patients with optic nerve sheath meningioma.

Results: Most patients were referred with progressive visual loss although several were fortuitously discovered when imaging was done for other reasons. Visual acuity ranged from 20/20 to NLP. Interestingly OCT had a very variable appearance at the time of diagnosis. Patients with relatively advanced disease could have NFL thinning and associated optic atrophy. Often patients with early involvement had normal nerve fiber layer thickness, or even thickening presumably related to constipation of axonal transport.

Conclusions: OCT is very useful for assessing the anatomy of the optic nerve, along with physiologic correlates such as afferent pupillary defect which can also be measured. Fractionated radiation therapy may substantially improve visual function. Not all patients are responsive. Disparity between improvement in psychophysical testing, such as acuity and automated perimetry and continued thinning of nerve fiber layer is common . This must be kept in mind when assessing patients with optic nerve sheath meningiomas and predicting results of radiation therapy.