Background Repetitive peripheral sensory stimulation (RPSS) delivered above the sensory threshold (RPSS SUPRA ) enhances motor performance and learning in the chronic phase after stroke. Here, we compared the effects of RPSS SUPRA and RPSS delivered at subsensory intensity (RPSS SUB ) on motor function and levels of γ-aminobutyric acid (GABA)+ (GABA plus coedited macromolecules) measured by proton magnetic resonance spectroscopy in the ipsilesional and contralesional primary motor cortex at different stages post-stroke. Methods In this multicenter, randomized proof-of-principle clinical trial, 51 participants in the early subacute or chronic phases after stroke were assigned to receive a single session of either RPSS SUPRA or RPSS SUB of the median nerve, followed by motor training. Jebsen–Taylor test (JTT) scores were assessed before RPSS, after RPSS, and after training. GABA+ ipsilesional/contralesional ratios (GABA+ ipsilesional/contralesional ) were calculated. The data were analyzed with generalized estimation equations with the factors INTERVENTION, GROUP, and TIME. Results The percent change in JTT performance was significantly affected by TIME, with greater improvements after training than after RPSS across groups. For absolute JTT scores, there was a significant INTERVENTION × GROUP × TIME interaction. In the subacute phase, JTT performance declined significantly post-RPSS SUPRA and improved significantly post-RPSS SUB , whereas in the chronic phase, performance improved significantly following both RPSS SUB and RPSS SUPRA ( P < .001 for all Bonferroni comparisons). GABA+ ipsilesional/contralesional ratios decreased significantly after RPSS SUPRA in the subacute phase ( P = .008) and remained unchanged in the other groups. Conclusions Subsensory and suprasensory RPSS have distinct effects on motor performance and M1 GABA+ levels in well-recovered individuals in the subacute and chronic phases post-stroke. Trial Registration: NCT03956407 (2019/05/20).
Conforto et al. (Mon,) studied this question.