LEMS – 3,4-Diaminopyridine Treatment — SCE Neurology MCQ

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ModeratePeripheral Neuropathy & NeuromuscularLEMS – 3,4-Diaminopyridine TreatmentSCE Neurology

A 50-year-old man is diagnosed with Lambert-Eaton myasthenic syndrome (anti-VGCC antibodies positive, incremental response on high-frequency RNS). CT chest reveals a small cell lung cancer. In addition to cancer treatment, what symptomatic treatment is available for LEMS?

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Correct answer: E — 3,4-diaminopyridine (amifampridine)

3,4-diaminopyridine (amifampridine) is the first-line symptomatic treatment for LEMS. It blocks presynaptic potassium channels, prolonging the nerve terminal action potential and increasing calcium influx, thereby enhancing acetylcholine release. It is available through a managed access programme in the UK. Pyridostigmine (a cholinesterase inhibitor) may provide modest additional benefit. Immunotherapy (IVIg, PLEX, steroids) addresses the autoimmune mechanism. A: Pyridostigmine is less effective in LEMS than MG because the primary defect is presynaptic. C: Rituximab is not first-line symptomatic therapy. D: Eculizumab is not used in LEMS. E: Apomorphine is for PD.

Reference: EAN/EFNS LEMS Guidelines; ABN LEMS Guidelines; BNF