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Optic neuritis — SCE Neurology MCQ

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HardNeuro-ophthalmologyOptic neuritisSCE Neurology

A 29-year-old develops painful monocular visual loss over three days, impaired colour vision and a relative afferent pupillary defect. The optic disc is normal, but examination also finds brisk legs and extensor plantar responses. Which investigation best evaluates the optic nerve and future demyelinating risk?

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Correct answer: D — Contrast-enhanced brain MRI with fat-suppressed orbital sequences

The best answer is “Contrast-enhanced brain MRI with fat-suppressed orbital sequences”. The syndrome is retrobulbar optic neuritis with additional central signs; dedicated contrast orbital imaging confirms optic-nerve inflammation while brain MRI assesses demyelinating lesions and alternative diagnoses. “Non-contrast CT of the head as the definitive optic-nerve study” is less appropriate because CT is insensitive to typical optic-nerve inflammation and demyelinating lesion burden “Carotid duplex ultrasonography without intracranial imaging” is less appropriate because carotid imaging does not evaluate this painful inflammatory optic neuropathy “Temporal-artery biopsy before obtaining inflammatory markers” is less appropriate because young age and the phenotype do not justify bypassing imaging for a giant-cell-arteritis pathway “Electroretinography alone to localise a retrobulbar optic neuropathy” is less appropriate because retinal physiology does not replace MRI when the lesion is behind a normal optic disc

Reference: Optic neuritis: a practical guide. https://pn.bmj.com/content/18/5/358 NICE NG220: Multiple sclerosis in adults — recommendations. https://www.nice.org.uk/guidance/ng220/chapter/Recommendations