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Hypokalaemic periodic paralysis — SCE Neurology MCQ

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HardNeuromuscularHypokalaemic periodic paralysisSCE Neurology

A 42-year-old has progressive sensory ataxia without weakness. Sensory and motor nerve conduction studies and needle EMG are normal. Tibial SSEPs are delayed, CSF protein is raised without cells, and contrast MRI shows cauda-equina root enhancement. Which diagnosis best fits?

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Reveal the answer and explanation

Correct answer: E — Chronic immune sensory polyradiculopathy

Explanation lettering: E = shown as C · C = shown as E

A should produce abnormalities in distal sensory or motor conduction if the sampled peripheral nerves are involved. B causes non-length-dependent sensory-potential loss because the dorsal-root ganglia are affected. C is correct: CISP affects proximal sensory roots, leaving routine nerve conduction and EMG normal while producing abnormal SSEPs, root enhancement and albuminocytological dissociation; response to IVIg supplies further support. D would require the vestibular-cerebellar phenotype and targeted genetics. E would need appropriate serology and typically different clinical context.

Reference: Chronic immune sensory polyradiculopathy: https://pn.bmj.com/content/22/1/57