Dual-tDCS combined with sensorimotor training promotes upper limb function in subacute stroke patients: A randomized, double-blinded, sham-controlled study

Background: Dual transcranial direct current stimulation (tDCS) over the bilateral primary somatosensory cortex (PSC) has potential benefits in stroke. In addition, compared with traditional rehabilitation training, sensorimotor training can significantly improve the sensorimotor function of patients. However, the efficacy of dual-tDCS combined with sensorimotor training in patients with subacute stroke is unknown.Objective: To assess whether dual-tDCS may enhance the efficacy of sensorimotor training on the upper limb functions in patients with subacute stroke. In addition, this study aims to explore the potential clinical mechanism of this combination therapy.Methods: We randomized 52 individuals with first-ever, unilateral subcortical stroke into the experimental group (n = 26) and the control group (n = 26). Patients in the experimental group received 20 min of dual-tDCS over the PSC and 40 min of sensorimotor training each session, while patients in the control group received sham dual-tDCS. The treatment cycle was a 1-h session of therapy each day, 5 days per week for 4 weeks. The Fugl-Meyer Assessment of Upper Extremity (FMA-UE) subscale, Action Research Arm Test (ARAT), Box and Block test (BBT), Erasmus MC revised Nottingham sensory assessment scale (Em-NSA), Neurometer sensory nerve quantitative detector (CPT), the Barthel index (BI), and Hospital Anxiety and Depression Scale (HADS) were used to assess upper limb function, activities of daily living (ADL), and mental health before and after the 4-week treatment period. In addition, functional near-infrared spectroscopy (fNIRS) was used to explore potential clinical brain mechanisms.Results: Both groups showed significant improvement in all clinical scales (All p < 0.05) after treatment. Compared with sham-tDCS plus sensorimotor training, active dual-tDCS coupled with sensorimotor training can significantly improve the FMA-UE, ARAT, Em-NSA-Stereognosis, and CPT-2K Hz. In addition, dual-tDCS combined with sensorimotor training can significantly activate the left pre-Motor and supplementary motor cortex (PM-SMC) and enhance the functional connection between the left somatosensory association cortex (SAC) and RPM-SMC. Furthermore, the difference of FMA-UE in the experimental group was positively correlated with the functional connectivity of RPM-SMC-LSAC (r = 0.815, p < 0.001).Conclusion: Dual-tDCS over the PSC combined with sensorimotor training can improve upper limb sensory and motor dysfunction, enhance ADL, and alleviate depression and anxiety for subacute stroke patients. Our results indicated that RPM-SMC-LSAC may be potential therapeutic targets for dual-tDCS in upper limb rehabilitation on stroke.