EP 143. Test-retest reliability of single and paired pulse transcranial magnetic stimulation parameters in healthy men and women

Question To determine the influence of different factors on test-retest reliability of frequently used transcranial magnetic stimulation (TMS) parameters while controlling for potential confounders in healthy subjects. Methods TMS was applied in 93 healthy volunteers (61% male) twice (mean retest interval of 34.0 ± 25.6 (SD) days) between 7 am and 2 pm by four investigators (sessions n investigator A  = 47, investigator B  = 95, investigator C  = 28, investigator D  = 16). Women were assessed only in their follicular phase. Test stimulus (TS), resting motor threshold (RMT), short latency intracortical inhibition (SICI), intracortical facilitation (ICF) and cortical silent period (SCP) were analyzed. CSP was analyzed visually and automatically. Results Good test-retest reliabilities were observed for TS ( r  = .880) and RMT ( r  = .826), moderate for visual and automated analyzed CSP durations (resp. r  = .466, r  = .486), and poor for ICF ( r  = −.159). Gender (eg. automated CSP women: r  = .538 vs. men: r  = .422), re-test interval and method of CSP-analysis did not influence reliabilities. Reliable change indices are reported. Conclusions In a large sample of healthy volunteers we found good to moderate test-retest reliabilities in all but one TMS-parameter. Automated analysis of the CSP did not prove to be more reliable than visual determination. For the first time it presents reliable change indices for all frequently used TMS parameters. These data can be helpful to determine the significance of observed changes in cortical excitability as well as for study design and sample size calculation in future research, in healthy populations.