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Safinamide – MAO-B Inhibitor — SCE Neurology MCQ

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HardMovement DisordersSafinamide – MAO-B InhibitorSCE Neurology

A marathon runner develops exertional rhabdomyolysis with CK 92,000 IU/L and acute kidney injury. He reports two previous exercise-induced episodes and a similarly affected brother. After recovery, a genetic panel is unrevealing and biopsy is planned. When should the biopsy ideally be performed to maximise diagnostic yield?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: E — Eight weeks later, using MRI to avoid end-stage muscle

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

C is correct: acute necrosis and regeneration can overwhelm the underlying diagnostic pathology, so specialist guidance recommends delaying muscle biopsy for about eight weeks after rhabdomyolysis. A clinically involved but not profoundly weak or fatty-replaced muscle is preferred, often guided by MRI. Immediate or one-week biopsy risks a nonspecific destructive picture; a recently needled muscle may add artefact. Waiting two years is unnecessary and risks losing an opportunity to investigate recurrent familial exertional rhabdomyolysis.

Reference: Muscle biopsy: what and why and when?: https://pn.bmj.com/content/20/5/385