Cathodal transcranial direct current stimulation for upper extremity functional rehabilitation in stroke survivors: a meta-analysis of parallel randomized controlled trials

Background Upper extremity motor dysfunction is common after stroke. Based on the inter-hemispheric inhibition model, cathodal transcranial direct current stimulation (c-tDCS) applied over the contralesional primary motor cortex (M1) is a promising adjuvant neuromodulation, but high-quality evidence for its efficacy, optimal parameters, and safety remains limited.Methods We searched 10 databases through January 25, 2026, for parallel randomized controlled trials (RCTs). Methodological quality was assessed using Cochrane Risk of Bias 2.0, and meta-analyses were performed using RevMan 5.4 and Stata/SE 15.1.Results Twenty-six RCTs (1038 patients) were included. Compared with controls, c-tDCS significantly improved upper extremity motor function, manual dexterity, and daily living activities, while also reducing elbow spasticity and overall neurological impairment (all p < 0.05). Resting motor threshold remained unchanged. Subgroup analyses showed stable efficacy at 1–2 mA, 20 min/session, 5 sessions/week, and ≥2 weeks of treatment. Short-term benefits were preserved, while long-term durability needs verification. Adverse events were mild and transient, mainly local tingling and itching.Conclusions Adjuvant c-tDCS improves upper limb motor function, daily living activities, elbow spasticity, and global neurological status in stroke survivors, with favorable safety and short-term durability. A regimen of 1–2 mA for 20 min, 5 sessions/week for ≥2 weeks is recommended.