Reliability of Motor Evoked Potentials Induced by Transcranial Magnetic Stimulation: The Effects of Initial Motor Evoked Potentials Removal

Abstract

Introduction:Transcranial magnetic stimulation (TMS) is a useful tool for assessment of corticospinal excitability (CSE) changes in both healthy individuals and patients with brain disorders. The usefulness of TMS-elicited motor evoked potentials (MEPs) for the assessment of CSE in a clinical context depends on their intra-and inter-session reliability. This study aimed to evaluate if removal of initial MEPs elicited by using two types of TMS techniques influences the reliability scores and whether this effect is different in blocks with variable number of MEPs.Methods:Twenty-three healthy participants were recruited in this study. The stimulus intensity was set at 120% of resting motor threshold (RMT) for one group while the stimulus intensity was adjusted to record MEPs up to 1 mV for the other group. Twenty MEPs were recorded at 3 time points on 2 separate days. An intra-class correlation coefficient (ICC) reliability with absolute agreement and analysis of variance model were used to assess reliability of the MEP amplitudes for blocks with variable number of MEPs.Results:A decrease in ICC values was observed with removal of 3 or 5 MEPs in both techniques when compared to all MEP responses in any given block. Therefore, removal of the first 3 or 5 MEPs failed to further increase the reliability of MEP responses.Conclusion:Our findings revealed that a greater number of trials involving averaged MEPs can influence TMS reliability more than removal of the first trials.

Comparison of Rossini–Rothwell and adaptive threshold‐hunting methods on the stability of TMS induced motor evoked potentials amplitudes

“…The findings of high intra‐session reliability of TMS‐elicited MEPs using both R–R and PEST methods are consistent with those of previous studies, which suggest that a stable estimates of MEPs separated by 20 min of no intervention can be achieved within a session (Bastani & Jaberzadeh, ; Christies et al, ; Hashemirad, Zoghi, Fitzgerald, & Jaberzadeh, ; Vaseghi et al, ). The results also suggest that MEP measurements obtained across two sessions 48 hr apart produces good reliabilities using either R–R or PEST methods.…”

Test-retest reliability of short-interval intracortical inhibition and intracortical facilitation in patients with schizophrenia

“…Further, our present study is highly comparable to previous research on SICI reliability which used RMT-based TS intensity (e.g., Corp et al, 2015; O’Leary et al, 2015; Ngomo et al, 2012). Despite the fact that the MEP amplitudes induced by TS here in bothgroups did not significantly differ from 1 mV and using 120%RMT or 1-mV did not lead to significantly different reliability (Hashemirad et al, 2017), it should still be cautious to generalize the satisfactory reliability of SICI in schizophrenia patients observed here to studies using 1-mV TS or other TS intensity in SICI.…”

Transspinal Direct Current Stimulation Produces Persistent Plasticity in Human Motor Pathways

“…Because the effects after a single DC stimulation session last up to a few hours after current offset 50 , 51 , the interval among sessions was sufficient for all neural changes due to tsDCS to have been abolished. Third, because the number of MEPs being acquired affects their reliability 52 , and baseline MEP variability is related to neuroplasticity protocols 53 , large scale studies incorporating I-wave protocols, which are known to contribute to baseline MEP variability, are needed. Optimal stimulation intensities for changes of corticospinal and spinal motor pathways following tsDCS also warrant further investigation, since anodal and cathodal tDCS effects are intensity-dependent manifested in a non-linear fashion 54 .…”