Optic nerve sheath meningioma with concurrent ovarian malignancy: A diagnostic and management challenge

Optic nerve sheath meningioma (ONSM) is a rare benign neoplasm arising from meningothelial arachnoid cap cells surrounding the intraorbital or intracanalicular optic nerve. It accounts for approximately 1–2% of all meningiomas and 2% of orbital tumors, with a female predominance (3:1) and peak incidence in the fourth to fifth decade. We report a 38-year-old diabetic female who presented with progressive left-sided proptosis and diminution of vision for one year. Examination revealed reduced visual acuity (6/60), axial proptosis, positive relative afferent pupillary defect, and optic disc edema. After an initial inconclusive orbital ultrasonogram, a contrast-enhanced MRI brain and orbit demonstrated a heterogeneous lesion at the left orbital apex encasing the optic nerve, with differentials of optic neuritis sequelae versus ONSM; a second contrast-enhanced MRI on a dedicated orbital protocol was consistent with an ONSM. Evaluation of a symptomatic palpable pelvic mass revealed a complex adnexal mass with elevated CA-125, necessitating prioritized surgical intervention for suspected ovarian malignancy. This case highlights the importance of comprehensive systemic evaluation in patients with orbital tumors. Although the clinical and radiological picture is that of a sporadic intraorbital ONSM, the concurrent ovarian lesion—histopathologically confirmed as a FIGO Stage IA endometrioid adenocarcinoma arising in endometriosis—most likely represents an incidental synchronous neoplasm rather than a true systemic association. A multidisciplinary approach facilitated successful staged management of both pathologies. Stereotactic fractionated radiotherapy remains the preferred treatment for ONSM with preserved vision.