A Patient with Exophytic Primary Optic Nerve Sheath Meningioma: Stratified Risk of Surgery Based on the Morphology

Primary optic nerve sheath meningioma (pONSM) is one of the most challenging tumors to manage. Although surgical excision may be considered a treatment option to maintain visual function, the safety of surgery remains debatable due to the non-negligible risk of optic nerve injury. pONSM often grows concentrically around the optic nerve; however, it can also demonstrate an exophytic growth from the optic nerve. The risk of surgical excision of pONSM may vary based on the tumor's growth pattern and area of contact with the optic nerve; however, there has been no detailed report on risk stratification to date. The authors present an illustrative case of an exophytic pONSM which was removed surgically without complications, suggesting that tumor morphology may also influence the surgical risk. In this report, the imaging and intraoperative features of exophytic pONSM are presented in detail, and the risk factors for complications are discussed.