OCT in MS – Axonal Loss Marker — SCE Neurology MCQ

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ModerateMultiple Sclerosis & CNS InflammationOCT in MS – Axonal Loss MarkerSCE Neurology

A 50-year-old woman with MS undergoes optical coherence tomography (OCT). It shows thinning of the peripapillary retinal nerve fibre layer (pRNFL) in both eyes, with the left eye more affected. She had left optic neuritis 3 years ago. What does OCT pRNFL thinning reflect in MS?

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Correct answer: A — Axonal loss in the optic nerve — a marker of neurodegeneration

OCT measures the thickness of the retinal nerve fibre layer, which is composed of unmyelinated retinal ganglion cell axons. In MS, pRNFL thinning reflects axonal loss (neurodegeneration) following optic neuritis or subclinical optic nerve damage. It correlates with visual acuity, contrast sensitivity, and overall brain atrophy. OCT is increasingly used as a biomarker of neurodegeneration in MS clinical trials and is being adopted in clinical practice for monitoring. A: Macular oedema causes thickening, not thinning. C: Active ON would show disc swelling/thickening acutely, not chronic thinning. D: Glaucoma also causes pRNFL thinning but in a different clinical context. E: Papilloedema causes thickening.

Reference: NICE NG100 MS (2022); Petzold et al. OCT in MS Consensus