Post-exercise exhaustion in Lambert-Eaton myasthenic syndrome

Objectives: To study post-exercise exhaustion by decrement (PEE-D) systematically in 24 repetitive nerve stimulation (RNS) tests in 14 patients with Lambert-Eaton myasthenic syndrome (LEMS). Methods: In the abductor digiti quinti muscle, the compound muscle action potential (CMAP) amplitude and 3. Hz responses for 2. s were obtained with the supramaximal stimulation at rest, immediately after (PE0), 30. s after (PE30s), and at 1, 2, 3, and 4. m after 10-s exercise. Results: There was a 377% increment in the CMAP amplitude at PE0 and a mild increment (+26%) at PE30s. A transient but significant improvement (-22%) in the decremental response was observed at PE0, and a gradual worsening of decrement in subsequent tests, with the worst decrement noted (-50%) at PE2m. Conclusion: PEE-D was found 2. m after exercise in LEMS. Significance: PEE-D may be physiologically closest to the reversible myasthenic fatigue after exercise observed in LEMS patients.