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.