Transcranial direct current stimulation for upper extremity motor dysfunction in poststroke patients: A systematic review and meta-analysis

Objective: To evaluate the efficacy and safety of transcranial direct current stimulation in poststroke patients with upper extremity motor dysfunction using a systematic review and meta-analysis. Data Sources: We searched the Web of Science, Cochrane Library, EMBASE, and PubMed for randomized controlled trials investigating the effects of both active and sham stimulation up until January 27, 2024. Review Methods Efficacy, including the upper extremity Fugl-Meyer Assessment, Action Research Arm Test, Barthel Index, and safety, were assessed. The risk of bias was assessed using the Cochrane Risk of Bias 2 tool and the Physiotherapy Evidence Database Scale. Meta-analysis was performed using the RevMan 5.4 software. Results: Forty-four studies with 1555 participants were included. Transcranial direct current stimulation proved effective in improving upper extremity motor function (standardized mean difference = 0.22, 95% confidence interval: 0.12-0.32, P < 0.001) and Barthel Index (mean difference = 4.65, 95% confidence interval: 2.82-6.49, P < 0.001). Subgroup analysis revealed the highest transcranial direct current stimulation efficacy in patients with subacute stroke. Both anodal and cathodal stimulation were effective against upper extremity motor dysfunction. C3/C4 was the most effective stimulus target. Optimal stimulation parameters included stimulus current densities <0.057 mA/cm(2) for 20-30 min and <30 sessions. Adverse effects and dropouts during follow-up showed that transcranial direct current stimulation is safe and feasible. Conclusions: Our findings suggest that both anodal and cathodal stimulation were significantly effective in subacute stroke patients, particularly when preceding other treatments and when C3/C4 is targeted.