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HSV encephalitis — SCE Neurology MCQ

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HardCNS InfectionsHSV encephalitisSCE Neurology

A 63-year-old woman has progressive painful stiffness confined initially to one leg, stimulus-triggered spasms, breast weight loss and continuous motor-unit activity at rest. GAD65 antibodies are negative. Which result would most strongly redirect the work-up toward a paraneoplastic stiff-limb syndrome?

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Reveal the answer and explanation

Correct answer: C — Amphiphysin antibody with urgent breast and systemic tumour assessment

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

A is correct: amphiphysin antibodies have a strong association with paraneoplastic stiff-person/stiff-limb phenotypes, particularly breast and lung malignancy, so tumour assessment is integral. B is more characteristic of PERM and does not remove cancer risk. C would require presynaptic neuromuscular-junction physiology. D and E do not fit continuous agonist–antagonist motor-unit activity with stimulus-triggered spasms. The negative GAD result should broaden antibody and cancer testing rather than dismiss the clinical syndrome.

Reference: Stiff-person syndrome: https://pn.bmj.com/content/25/1/6 Paraneoplastic neurological syndromes: a practical approach to diagnosis and management: https://pn.bmj.com/content/22/1/19