Transcranial direct current stimulation (tDCS): does it have merit in stroke rehabilitation? A systematic review

Transcranial direct current stimulation has been gaining increasing interest as a potential therapeutic treatment in stroke recovery. We performed a systematic review with meta-analysis of randomized controlled trials to collate the available evidence in adults with residual motor impairments as a result of stroke. The primary outcome was change in motor function or impairment as a result of transcranial direct current stimulation, using any reported electrode montage, with or without adjunct physical therapy. The search yielded 15 relevant studies comprising 315 subjects. Compared with sham, cortical stimulation did not produce statistically significant improvements in motor performance when measured immediately after the intervention (anodal stimulation: facilitation of the affected cortex: standardized mean difference = 0.05, P = 0.71; cathodal stimulation: inhibition of the nonaffected cortex: standardized mean difference = 0.39, P = 0.08; bihemispheric stimulation: standardized mean difference = 0.24, P = 0.39). When the data were analyzed according to stroke characteristics, statistically significant improvements were evident for those with chronic stroke (standardized mean difference = 0.45, P = 0.01) and subjects with mild-to-moderate stroke impairments (standardized mean difference = 0.37, P = 0.02). Transcranial direct current stimulation is likely to be effective in enhancing motor performance in the short term when applied selectively to patients with stroke. Given the range of stimulation variables and heterogeneous nature of stroke, this modality is still experimental and further research is required to determine its clinical merit in stroke rehabilitation.