A 52-year-old woman presents with slowly progressive painless visual loss in the right eye over two years, mild proptosis, and normal fundus initially. Contrast-enhanced CT shows thickening of the right optic nerve with enhancement of its sheath producing a 'tram-track' appearance. The diagnosis is:
- A Optic nerve glioma
- B Sarcoid optic neuropathy
- C Optic nerve sheath meningioma ✓
- D Orbital pseudotumour
Correct answer: C. Optic nerve sheath meningioma
Explanation
The tram-track sign, parallel linear enhancement outlining a non-enhancing compressed optic nerve, is characteristic of an optic nerve sheath meningioma arising from arachnoid cap cells of the nerve sheath. It typically affects middle-aged women with gradual visual loss, transient visual obscurations and later optociliary shunt vessels on the disc. An optic nerve glioma enlarges the nerve fusiformly with intrinsic tumour enhancement rather than sheath-only enhancement, and occurs mainly in children, often with neurofibromatosis type 1.
Reference: Kanski's Clinical Ophthalmology, 9th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.