ABSTRACT
INTRODUCTION: To find the best exercise duration for postexercise exhaustion by decrement (PEE-D) in myasthenia gravis (MG). METHODS: In 32 tests in 32 MG patients, repetitive nerve stimulation was performed in the abductor digiti quinti muscle. The 3 Hz responses for 2 s were obtained with supramaximal stimulation at rest, and immediately after (PE0), 30 s after (PE30s), and 1, 2, 3, and 4 min after 10-s, 30-s, and 1-min exercises. RESULTS: Compared with the decrement at rest, a significantly greater decrement was found at PE2m and PE3m after 30-s exercise, and at PE2m, PE3m, and PE4m after 1-min exercise. In 11 patients who showed a decremental response only with exercise, PEE-D was observed in 5 after 30-s exercise and in 8 after 1-min exercise. CONCLUSIONS: One-minute exercise is best for evaluation of PEE-D in MG.
Subject(s)
Exercise/physiology , Muscle Fatigue/physiology , Myasthenia Gravis/diagnosis , Action Potentials/physiology , Adult , Aged , Antibodies , Electric Stimulation , Electromyography , Female , Humans , Male , Middle Aged , Myasthenia Gravis/physiopathology , Neurologic Examination , Prospective Studies , Receptor Protein-Tyrosine Kinases/immunology , Receptors, Cholinergic/immunologyABSTRACT
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 3Hz responses for 2s were obtained with the supramaximal stimulation at rest, immediately after (PE0), 30s after (PE30s), and at 1, 2, 3, and 4m 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 2m after exercise in LEMS. SIGNIFICANCE: PEE-D may be physiologically closest to the reversible myasthenic fatigue after exercise observed in LEMS patients.
