Reliability of Transcranial Magnetic Stimulation Measures

Abstract

Measurements of motor cortex inhibition and excitability can provide useful insights when assessing pathological damage as well as neuronal recovery from injuries. PURPOSE: The aim of this study was to determine the reliability of single pulse transcranial magnetic stimulation (TMS) measures in men and women. METHODS: Nine (5 female) healthy college age participants were tested at three time points, each separated by one week. Single pulse TMS was delivered to the contralateral motor cortex of the dominant first dorsal interosseous. Resting motor threshold (RMT) and the peak-to-peak amplitude of motor evoked potentials (MEP) at 120% RMT were used to quantify motor cortex excitability. The duration of the cortical silent period (CSP), evoked at 120% RMT while participants maintained a contraction at 50% of maximum force, was used to quantify motor cortex inhibition. Reliability was assessed with the intraclass correlation coefficient (ICC 2,1). RESULTS: There was no significant difference across time (p=0.82; p=0.83; p=0.70) or between sexes (p=0.83; p=0.68; p=0.36) for RMT, MEP, or CSP, respectively. Also, there was no significant sex by time interaction (p≥0.34) for any of the measures. Reliability across days was strong for RMT (R=0.69), and very strong for MEP (R=0.87) and CSP (R=0.95). CONCLUSIONS: These results support the use of single pulse TMS measurements to reliably assess and track motor cortex physiological function in men and women.