Comparison of 4 Methods to Estimate the Resting Motor Threshold Using Transcranial Magnetic Stimulation

BACKGROUND: Estimating the resting motor threshold (RMT) is crucial for both investigative and therapeutic transcranial magnetic stimulation. However, no gold standard exists, as each method involves trade-offs between accuracy, time, and ease of use. This study compared RMT estimates and trial requirements across 4 EMG-based methods-Rossini-Rothwell (RR), maximum likelihood parameter estimation by sequential testing (ML-PEST), Mills-Nithi (MN), supervised parametric estimation (SPE)-and 2 visual methods: RR visual and ML-PEST visual. METHODS: In this observational study, RMT was estimated in 20 healthy participants using 6 approaches: 4 EMG-based (RR, ML-PEST, MN, SPE) and 2 visual (RR and ML-PEST). We assessed agreement among EMG-based methods and compared RMT estimates and trial counts across all methods. RESULTS: EMG-based methods showed strong agreement (ICC: 0.97, 95% CI: 0.94-0.99). RMT estimates differed significantly (P=0.001), with RR Visual yielding the highest values-significantly higher than RR EMG, ML-PEST EMG, and SPE EMG methods. Trial counts also varied (P