Contrast-enhanced MRI of a 45-year-old woman with slowly progressive painless proptosis and mild visual blurring shows diffuse thickening of the left intraorbital optic nerve with enhancement of its surrounding sheath, producing parallel lines of signal on either side of a non-enhancing central nerve. The most likely diagnosis is:

• A Orbital pseudotumour
• B Optic nerve glioma
• C Optic neuritis
• D Optic nerve sheath meningioma ✓

Explanation

The 'tram-track' sign, enhancement of the dural sheath with a spared non-enhancing nerve between two enhancing lines, is characteristic of optic nerve sheath meningioma, typically seen in middle-aged women with gradual proptosis and slowly progressive visual loss. An optic nerve glioma instead expands and enhances the nerve substance itself, obliterating the tram-track pattern, which is the key distinguishing feature. Optic neuritis enhances the nerve diffusely rather than the sheath circumferentially.

Reference: Kanski's Clinical Ophthalmology, 9th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.