Uni-hemispheric dual-site anodal tDCS (M1-DLPFC) for upper limb motor function and spasticity in chronic stroke: a randomized clinical trial

Background/objectives Upper extremity impairment significantly affects motor function and quality of life after stroke. This study investigated the safety and efficacy of a non-invasive brain stimulation approach, uni-hemispheric concurrent dual-site anodal transcranial direct current stimulation (a-tDCS) targeting the primary motor cortex (M1) and dorsolateral prefrontal cortex (DLPFC), to improve upper extremity performance in chronic stroke. Methods This double-blind, randomized, sham-controlled study involved 38 chronic stroke patients to evaluate the safety and efficacy of uni-hemispheric concurrent dual-site anodal transcranial direct current stimulation (a-tDCS). Participants were randomly assigned to one of two groups: experimental group 1 (a-tDCS at 2 mA targeting M1 and DLPFC concurrently) or experimental group 2 (active a-tDCS at 2 mA over M1 with sham stimulation over DLPFC), with each receiving 20-min sessions over five consecutive days. Upper extremity motor function (Fugl-Meyer Assessment—FMA) and spasticity (Modified Modified Ashworth Scale—MMAS) were assessed at baseline and 24 h following the final intervention. The procedure was deemed safe. Statistical analysis involved the U Mann–Whitney test for between-group comparisons and the Wilcoxon signed-rank test for within-group changes. Results The results demonstrated that uni-hemispheric concurrent dual-site a-tDCS targeting M1 and DLPFC in experimental group 1 did not lead to statistically significant improvements in upper extremity motor function, elbow and wrist flexor spasticity, or range of motion in this cohort of chronic stroke patients. Furthermore, no statistically significant differences were found between experimental group 1 and experimental group 2 (the sham control group) for any of the measured outcomes ( p ≥ 0.05). Conclusion Uni-hemispheric concurrent dual-site a-tDCS targeting both M1 and DLPFC did not demonstrate a superior effect on upper extremity motor recovery compared to a-tDCS applied solely to M1 in chronic stroke patients.