LAMBERT-EATON MYASTHENIC SYNDROME WITH PROMINENT POSTEXERCISE EXHAUSTION

A 66-year-old man with Lambert-Eaton myasthenic syndrome, polyneuropat hy, and small cell lung cancer, developed profound muscle weakness wit h a prolonged period of ventilatory dependency. Electrophysiological s tudies demonstrated very small compound muscle action potentials in re sponse to supramaximal nerve stimulation, limited tetanic and postexer cise facilitation, and prolonged prominent postexercise exhaustion (40 -60% of baseline value) persisting up to 20 minutes. It is hypothesize d that these changes may reflect both a severe defect in acetylcholine release and decreased availability of releasible acetylcholine from t he terminal axon.