Contrast-enhanced CT of a middle-aged woman with slowly progressive painless visual loss shows thickening of the intraorbital optic nerve with calcification outlining the nerve, producing a tram-track appearance. The MOST likely diagnosis is:

• A Optic nerve glioma
• B Optic nerve sheath meningioma ✓
• C Orbital pseudotumour
• D Metastatic deposit to the optic nerve

Explanation

Optic nerve sheath meningioma arises from arachnoid cap cells around the nerve and calcifies, giving the characteristic tram-track or railroad-track sign on axial imaging where enhancing tumour surrounds a central non-enhancing nerve. Optic nerve glioma fusiformly enlarges and tortuosities the nerve itself without peripheral calcification, and typically presents in childhood, 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.