INTRODUCTIONPrimary optic nerve sheath meningiomas (ONSMs) are the most common primary tumours of the optic nerve sheath. The diagnosis and management of ONSMs have changed dramatically in the last decade. In this review article, we discuss the latest information regarding these issues.

MATERIALS AND METHODSReferences for this manuscript were obtained by searching the database PubMed using the phrase "optic nerve sheath meningioma". Approximately 150 articles were identified and reviewed. These articles served as reference sources for other articles, books and chapters on the subject. The results were combined with our personal experience, which includes over 100 cases of ONSMs that have been observed or treated with one or more of the modalities described below.

RESULTSThe diagnosis of ONSM can be suspected in most cases from clinical findings and supported by the results of neuroimaging, obviating tissue biopsy in the majority of cases. Management depends on several factors. Observation may be appropriate in patients with mild or no visual deficit or in whom visual loss is not progressing, whereas stereotactic fractionated radiation therapy has been documented to improve or stabilise vision in progressive or advanced cases. Attempts at excision of ONSMs are associated with a high risk of blindness and should be reserved for the rare case of an anteriorly located, primarily exophytic tumour with focal involvement of the dural sheath. Rare patients with acute visual deterioration may benefit from optic nerve sheath fenestration.

CONCLUSIONThe majority of ONSMs can be suspected on clinical grounds and diagnosed with readily available non-invasive neuroimaging. Stereotactic fractionated radiotherapy is currently the treatment of choice for ONSMs that require therapy.