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Isaac Syndrome – Acquired Neuromyotonia — SCE Neurology MCQ

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HardClinical NeurophysiologyIsaac Syndrome – Acquired NeuromyotoniaSCE Neurology

A 55-year-old has continuous myokymia, painful stiffness, hyperhidrosis and EMG neuromyotonic discharges with high-titre CASPR2 antibodies. Carbamazepine and gabapentin at maximally tolerated doses have not controlled disabling symptoms. Initial CT chest shows no tumour. Which escalation best addresses the expected treatment kinetics?

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Correct answer: A — Plasma exchange or intravenous immunoglobulin, followed by an immunotherapy plan

CASPR2-associated acquired neuromyotonia is an immune-mediated peripheral nerve hyperexcitability syndrome. When disabling symptoms persist after membrane-stabilising drugs, plasma exchange or intravenous immunoglobulin can provide relatively rapid immune treatment, followed where needed by corticosteroid or steroid-sparing planning. Azathioprine has delayed onset and is not a one-week rescue strategy. Rituximab may have a role in refractory autoimmune disease but is not the fastest isolated symptomatic intervention, while escalating an already dose-limited channel blocker or using focal botulinum toxin does not address diffuse antibody-mediated hyperexcitability. Malignancy surveillance remains relevant after an initially negative scan.

Reference: Isaacs’ syndrome: clinical and paraclinical perspectives in a series of cases: https://pmc.ncbi.nlm.nih.gov/articles/PMC11489630/