Reliability of TMS-related measures of tibialis anterior muscle in patients with chronic stroke and healthy subjects

A lack of normative data for transcranial magnetic stimulation (TMS)-related measures of the lower limb muscles in patients with stroke prevents us from understanding whether changes in TMS-related measures are induced by treatment or are due to their variability and/or the natural evolution of the disease. The purpose of this study was to determine the reliability of three TMS-related measures: motor threshold (MT), motor evoked potential latency (MEP Lat) and MEP amplitude (MEP Amp), linked to the corticospinal control of the tibialis anterior (TA) muscle in sixteen patients with chronic stroke and in sixteen aged-matched healthy subjects. Test-retest reliability was estimated using the intraclass correlation coefficient (ICC) with its 95% confidence interval (95% CI) and standard error of measurement (SEM). In healthy subjects the reliability of all the TMS-related measures yielded an ICC ≥ 0.75. Similar reproducibility levels were found in patients with chronic stroke, with the exception of MEP Amp on the paretic side (ICC = 0.38). These results suggest that the TMS-related measures investigated are reliable both in healthy subjects and, with the exception of MEP Amp on the paretic side, in patients with chronic stroke.