The efficacy of transcranial direct current stimulation on upper extremity motor function after stroke: A systematic review and comparative meta-analysis of different stimulation polarities

Abstract

Background:The efficacy of transcranial direct current stimulation (tDCS) hasbeen studied extensively. The cathodic (c-tDCS), anodic (a-tDCS), and bihemi-spheric stimulation have demonstrated efficacy in the management of theparetic upper extremity (UE) after stroke, but it has not been determined whichstimulation polarity has, so far, shown the best results.Objective:To evaluate the available evidence to determine which tDCS polar-ity has the best results in improving UE motor function after stroke.Methods:PubMed, PEDro, Web of Science, EMBASE, and SCOPUS data-bases were searched. Different Medical Subject Headings (MeSH) terms werecombined for the search strategy, to cover all studies that performed a compari-son between different tDCS configurations focused on UE motor rehabilitationin people with lived experience of stroke.Results:Fifteen studies remained for qualitative analysis and 12 for quantita-tive analysis. Non-significant differences with a 95% confidence interval(CI) were obtained for c-tDCS versus a-tDCS (g=0.10, 95% CI= 0.13;0.33,p=.39,N=292), for a-tDCS versus bihemispheric (g=0.02, 95%CI= 0.46; 0.42,p=.93,N=81), and for c-tDCS versus bihemispheric(g=0.09, 95% CI= 0.84; .66,p=.73,N=100). No significant differencesbetween the subgroups of the meta-analysis were found.Conclusions:The results of the present meta-analysis showed no evidencethat a stimulation polarity is superior to the others in the rehabilitation of UEmotor function after stroke. A non-significant improvement trend was observedtoward c-tDCS compared to a-tDCS