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Optic Nerve Sheath Meningioma — SCE Neurology MCQ

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HardNeuro-ophthalmologyOptic Nerve Sheath MeningiomaSCE Neurology

A 60-year-old man presents with progressive visual loss in the right eye. Visual acuity is 6/60 on the right. Fundoscopy shows right optic disc pallor. Left visual acuity is 6/6 with a normal disc. MRI orbits shows fusiform enlargement and enhancement of the right optic nerve sheath without nerve expansion. CT shows calcification within the lesion. What is the most likely diagnosis?

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Correct answer: A — Optic nerve sheath meningioma

Optic nerve sheath meningioma (ONSM) presents with progressive painless visual loss, optic atrophy, and the classic 'tram-track sign' on CT/MRI (calcification within the meningeal sheath surrounding but not expanding the optic nerve). On MRI, the lesion enhances with gadolinium and shows fusiform thickening of the optic nerve sheath. It is most common in middle-aged women. Treatment options include observation, fractionated stereotactic radiotherapy, or surgical resection (which sacrifices vision in the affected eye). A: Optic neuritis is painful with disc swelling acutely. C: Optic nerve glioma expands the nerve itself and occurs in children/NF1. D: Thyroid eye disease enlarges extraocular muscles. E: Sarcoidosis typically enhances the nerve, not the sheath.

Reference: NICE NG99; ABN Neuro-ophthalmology Guidelines