Transcranial direct current stimulation for upper and lower limb motor dysfunction after stroke: a systematic review and meta-analysis of randomized controlled trials

Transcranial direct current stimulation (tDCS) has emerged as a promising noninvasive intervention for motor recovery after stroke, yet its therapeutic efficacy remains unclear. This study was designed to systematically evaluate the effectiveness of a tDCS intervention for upper and lower extremity motor function in stroke patients. A comprehensive search was conducted for randomized controlled trials published before February 6, 2025, across five databases: PubMed, Embase, Web of Science, Cochrane Library, and Scopus. The Fugl-Meyer Assessment Scales for Upper and Lower Extremities served as primary evaluation metrics, complemented by secondary measures, including the Action Research Arm Test, Timed Up and Go Test, and Barthel Index. Two independent investigators screened the literature, and the Cochrane Risk of Bias Assessment Tool was employed to assess study quality and extract relevant data. A total of 24 randomized controlled trials were included in the analysis. Meta-analysis of the primary outcomes revealed that tDCS had a positive effect on improving lower limb motor function after stroke (mean difference ( MD ) = 1.628, 95% confidence interval ( CI ): 1.145-2.111, P < 0.001) but not on upper limb motor improvement ( MD = 1.133, 95% CI : –0.031–2.298, P = 0.056). Subgroup analyses revealed the optimal intervention parameters: anodal stimulation of the M1 region ( MD = 1.707, 95% CI : 1.159–2.256), current intensity ≥ 0.05 mA/cm 2 ( MD = 1.652, 95% CI : 0.862–2.442), and treatment duration exceeding 2 weeks ( MD = 1.848, 95% CI : 0.703–2.994). Notably, therapeutic benefits were particularly evident during the acute and subacute rehabilitation phases. Current evidence suggests that tDCS demonstrates clinically meaningful enhancement of lower limb motor rehabilitation in acute and subacute stroke patients, whereas its efficacy for upper extremity functional recovery remains inconclusive.