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MS Relapse Definition – 24-Hour Duration — SCE Neurology MCQ

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EasyMultiple Sclerosis & CNS InflammationMS Relapse Definition – 24-Hour DurationSCE Neurology

A 40-year-old woman with MS on no DMT develops acute bilateral leg weakness with a sensory level at T10 and urinary retention. MRI spine shows a short-segment T2 lesion at T9–T10 with gadolinium enhancement. This is her second clinical event (the first was optic neuritis 2 years ago). She is diagnosed with a clinical relapse. Per NICE NG100, what is the minimum duration of a clinical event to qualify as an MS relapse?

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Correct answer: E — 24 hours

Explanation lettering: B = shown as A · D = shown as B · A = shown as C · E = shown as D · C = shown as E

NICE NG100 and the 2017 McDonald criteria define an MS relapse as a clinical event attributable to CNS inflammation lasting at least 24 hours, in the absence of fever or infection (which can cause pseudo-relapses via Uhthoff phenomenon). The 24-hour criterion helps distinguish true relapses from transient symptom fluctuations. A/B: Too short — transient worsening from heat or fatigue can last hours. D/E: Too long — the 24-hour criterion is the established standard.

Reference: NICE NG100 MS (2022); McDonald Criteria (2017)