Optic nerve sheath schwannoma: illustrative case.

backgroundIn this case report, the authors discuss the diagnosis and treatment of a rare primary optic nerve sheath schwannoma (ONSS). Typically, intracranial schwannomas arise from the vestibular division of cranial nerve VIII and seldom cranial nerves V and VII. This case underscores the need for further documentation of ONSS to better understand its origins, refine diagnostic approaches, and optimize management strategies to enable earlier detection and better outcomes for patients' vision. OBSERVATIONS: The authors present the case of a 36-year-old patient who presented via an ophthalmologist due to visual loss in the left eye. She was initially treated for optic neuritis before further deterioration prompted repeat imaging, demonstrating a left extraorbital lesion distal to the optic chiasm. The patient underwent a complete resection of the lesion via pterional craniotomy in July 2024. LESSONS: The authors report the 17th case of ONSS in the literature. Despite the optic nerve's usual myelination pattern, these tumors can form, likely originating from ectopic Schwann cells or perioptic sympathetic fibers. Resection via a pterional approach enabled complete removal without postoperative complications. Because of the rarity of ONSS, further study is essential to enhance diagnosis, treatment, and surgical strategies. https://thejns.org/doi/10.3171/CASE25156.