Assessment of the compound muscle action potential amplitude return time between exercises or tests in the repetitive nerve stimulation test for Lambert‐Eaton myasthenic syndrome

Abstract

Introduction: When performing postexercise facilitation (PEF) as part of the repetitive nerve stimulation (RNS) test in Lambert-Eaton myasthenic syndrome (LEMS), it is important to avoid any influence of the previous exercise or RNS test on the compound muscle action potential (CMAP) amplitude. Methods: To measure the CMAP amplitude return time (ART) to that at rest, a single CMAP was obtained every 30 seconds until the amplitude was within 5% of that at rest in three exercise periods (10, 20, and 30 seconds) and in 10-second postexercise (PE) 3-Hz RNS testing with 17 tests in 10 LEMS patients. Results: Adequate ART between tests is 150 seconds for 10-second exercise (Ex) and 10-second PE 3-Hz RNS test, 120 seconds for 20-second Ex, and 90 seconds for 30-second Ex. Discussion: We recommend 150 seconds as adequate ART between the PEF test and the next test when performing RNS test in LEMS.

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“…For ensuring an adequate technical test, brief 10 s exercise and a 2.5 min wait period between the tests are recommended. 17 18 …”

Neuromuscular junction disorders beyond myasthenia gravis

“…2) [7]. For the proper RNS testing, 10 s brief exercise test and 2.5 m waiting period between tests are recommended [8,9]. For assessment of facilitation, !…”

“…2) [7]. For the proper RNS testing, 10 s brief exercise test and 2.5 m waiting period between tests are recommended [8,9]. For assessment of facilitation, ≥ 100% increment in the CMAP at HRS or after 10 s exercise test is pathognomonic of LEMS [2].…”