Unveiling the Enigma: Optic Nerve Sheath Meningioma Masquerading as Optic Neuritis

A 37-year-old female came with complaints of sudden vision loss in her left eye for the past 4 days along with pain when rotating her eyeball. Vision in her left eye was 6/9. Fundus examination revealed a grade 3 disc edema in the left eye. Visual evoked potential showed increased latency P100 (120 ms) in the left eye. MRI of the brain and orbit with contrast enhancement revealed a diffusely thickened left optic nerve sheath complex presenting a tram track appearance. The patient was diagnosed with optic nerve sheath meningioma and referred to an oncologist for fractionated stereotactic radiotherapy.