AUTHOR=Bashir Shahid , Yoo Woo-Kyoung , Kim Hyoung Seop , Lim Hyun Sun , Rotenberg Alexander , Abu Jamea Abdullah 

TITLE=The Number of Pulses Needed to Measure Corticospinal Excitability by Navigated Transcranial Magnetic Stimulation: Eyes Open vs. Close Condition

JOURNAL=Frontiers in Human Neuroscience

VOLUME=11

YEAR=2017

URL=https://www.frontiersin.org/journals/human-neuroscience/articles/10.3389/fnhum.2017.00121

DOI=10.3389/fnhum.2017.00121

ISSN=1662-5161

ABSTRACT=<p><bold>Objective</bold>: Motor evoked potentials (MEPs) obtained by transcranial magnetic stimulation (TMS) enable measures of the corticospinal excitability (CSE). However the reliability of TMS-derived CSE measures is suboptimal due to appreciable pulse-to-pulse MEP amplitude variability. We thus calculated how many TMS–derived MEPs will be needed to obtain a reliable CSE measure in awake adult subjects, in the eyes open (EO) and eyes closed (EC) conditions.</p><p><bold>Methods</bold>: Twenty healthy adults (70% male) received 40 consecutive navigated TMS pulses (120% resting motor threshold, RMT) in the EO or EC conditions on two separate days in randomized order.</p><p><bold>Results</bold>: For either the EO or EC condition, the probability that the 95% confidence interval (CI) derived from consecutive MEP amplitude measured included the true CSE, increased when the number of consecutive stimuli increased (EO: <italic>p</italic> = 0.05; EC: <italic>p</italic> = 0.001). No significant effect of RMT, Mini-Mental State Examination (MMSE) score, or gender on the CSE estimates was identified. At least 34 consecutive stimuli were required to obtain a most reliable CSE estimate in the EO condition and 31 in the EC condition.</p><p><bold>Conclusion</bold>: Our findings indicate that &gt;30 consecutive MEPs may be necessary in order to obtain a CSE measure in healthy adults.</p>