Inter-Pulse Interval Affects the Size of Single-Pulse Tms-Induced Motor Evoked Potentials: A Reliability Study

introduction: measuring the size of motor evoked potentials (meps) induced by transcranialmagnetic stimulation (tms) is an investigational technique to show the level of corticospinalexcitability; however, some of the fundamental methodological aspects of tms (such as theeffects of inter-pulse intervals (ipi) on mep size) are not fully understood, this issue raisesconcerns about the reliability of meps, especially in pre-test post-test studies. methods: mep size at short and long ipis was assessed during two separate sessions. inter- andintra-session reliability of mep size also was assessed at both short and long ipis. results: the results indicated that long ipis induced larger meps (p < 0.05) across all time points.the intra-class correlation coefficient (icc) indicated high intra- and inter-session reliability forshort (0.87 to 0.96) and long (0.80 to 0.97) ipis respectively. the amplitude of meps also hadhigh intersession reliability for short (icc = 0.87) and long (icc = 0.80) ipis. conclusion: this study provides evidence that the length of ipis determines the size of meps. asa result, it is recommended to add the length of ipi to the international checklist of considerationsfor tms application.