Reliability of lower limb transcranial magnetic stimulation outcomes in the ipsi- and contralesional hemispheres of adults with chronic stroke.

Abstract : Objective: To investigate the ability of transcranial magnetic stimulation (TMS) outcomes in the chronic stroke population to (i) track individual plastic changes and (ii) detect differences between individuals. To this end, intrarater ‘‘test-retest” reliability (relative and absolute) was tested for the ipsilesional and contralesional hemispheres. Methods: Thirteen participants with a unilateral stroke (6 months ago) and sensorimotor impairments were enrolled. Single and paired-pulse TMS outcomes were obtained from the primary motor cortex (M1) representation of the tibialis anterior muscle in both hemispheres and at two sessions separated by one week. The standard error of the measurement (SEMeas), minimal detectable change (MDC) and intraclass correlation coefficient (ICC) were studied. Results: Active motor threshold and latency of motor evoked potentials provided the lowest SEMeas and highest ICCs for both ipsi- and contralesional hemispheres. However, MDC were generally large, thus questioning the use of TMS outcomes to track individual plastic changes of M1. Conclusions: Our study provided supporting evidence of good to excellent intrarater reliability for a few TMS outcomes and proposed recommendations on the interpretation and the use of that knowledge in future work. Significance: Psychometric properties of TMS measures should be further addressed in order to better understand how to refine their use in clinical settings.