Timing of Decremental Response During Repetitive Nerve Stimulation in Myasthenia Gravis

Background: A decrement >10% detected during repetitive nerve stimulation (RNS) is supportive of considering a diagnosis of myasthenia gravis (MG). Several studies have found that most of this decrement is seen between 4 to 6 min post-exercise. However, there are not available studies analyzing if shorter timing would be sufficient.   Objective: The objective of this study was to evaluate if RNS up to 2 min post-exercise is sufficient to detect a decrement response >10%. Methods: We performed a retrospective chart review study of patients referred to our neuromuscular clinic at The University of Kansas Medical Center with symptoms suggestive of MG from 2013 to 2017. Results: A total of 76 patients with MG and 100 controls were identified.  A significant decrement was detected in 95% of MG patients with abnormal RNS within 2 minutes post-exercise. Conclusion: RNS up to 2 min post-exercise might be sufficient to detect a significant decrement in MG patients.