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Lambert-Eaton Syndrome — RACP Adult Medicine MCQ

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ModerateNeurologyLambert-Eaton SyndromeRACP Adult Medicine

A 55-year-old man with small cell lung carcinoma presents with proximal weakness that improves with repeated effort. Deep tendon reflexes are initially absent but return after sustained contraction. EMG shows incremental response with repetitive nerve stimulation at high frequency. Anti-VGCC antibodies are positive. What is the most likely diagnosis?

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Correct answer: C — Lambert-Eaton syndrome

Proximal weakness improving with repeated use (post-exercise facilitation), initially absent reflexes that return after contraction, incremental response on repetitive nerve stimulation, anti-VGCC antibodies, and associated SCLC is Lambert-Eaton myasthenic syndrome (LEMS). It is a paraneoplastic disorder in 50–60% of cases. Treatment addresses the underlying malignancy; 3,4-diaminopyridine improves symptoms.

Reference: eTG Neurology – 2024 – Paraneoplastic Syndromes; EFNS/ENS 2010 LEMS