Transcranial direct current stimulation and suppression of contralesional primary motor cortex post-stroke: a systematic review and meta-analysis

Objective: The purpose of this systematic review and meta-analysis was to investigate the therapeutic effects of cathodal tDCS (ctDCS) that suppresses the contralesional primary motor cortex (cM1) activity for individuals with stroke in different recovery phases.Methods: Fifteen studies that used ctDCS for suppressing the cM1 activity were included in this meta-analysis. Twenty total comparisons from the qualified studies identified motor function changes between ctDCS and sham protocols. We divided recovery stages into two categories: (a) acute and subacute phases (time since stroke6months): eight comparisons and (b) chronic phase (time since stroke>6months): 12 comparisons.Results: Random-effects meta-analysis models revealed motor improvements after applying ctDCS on the cM1 as indicated by a significant standardized effect size (ES=0.61; P<0.001). The moderator variable analysis showed that acute and subacute patients revealed no significant effect size of ctDCS (ES=0.46; P=0.07), whereas the ctDCS protocol significantly improved motor functions in chronic patients (ES=0.71; P<0.001).Conclusion: This comprehensive meta-analysis indicates that the treatment effects of ctDCS on the cM1 are different between patients in the acute and subacute phases and patients in the chronic phase post-stroke.