The impact of combined cerebellar transcranial alternating current stimulation and repetitive motor training on upper limb recovery in stroke patients

Background: Upper limb motor impairment is a common and disabling consequence of stroke, often showing limited recovery with conventional rehabilitation. Non-invasive brain stimulation (NIBS), particularly transcranial alternating current stimulation (tACS), has emerged as a promising neuro-modulatory technique; however, the effects of cerebellar tACS remain underexplored. Objective: To investigate the efficacy of cerebellar tACS combined with repetitive motor training (RMT) on upper limb motor recovery in patients with subacute ischemic stroke. Methods: In this randomized, double-blind, sham-controlled trial, 52 patients with subacute ischemic stroke and unilateral upper limb hemiparesis were randomly assigned to receive either active cerebellar tACS or sham stimulation. Active tACS (70 Hz, 1 mA, 20 minutes) was delivered prior to daily RMT sessions (60 min/day, 5 days/week for 3 weeks). The primary outcome was upper limb motor function (Fugl-Meyer Assessment for Upper Extremity; FMA-UE). Secondary outcomes included manual dexterity (Box and Block Test; BBT), spasticity (Modified Ashworth Scale; MAS), and hand grip strength. Assessments were conducted at baseline, post-intervention, and 4-week follow-up by blinded evaluators. Results: Participants receiving active tACS demonstrated significantly greater gains in FMA-UE (+11.2 vs. +3.8; p = 0.01), BBT (+7.1 vs. +1.8 blocks/min; p = 0.03), MAS (p = 0.04), and grip strength (+4.8 kg vs. +1.9 kg; p = 0.02) compared to the sham group. A large effect size was observed for FMA-UE (Cohen’s d > 0.8). Conclusion: Cerebellar tACS combined with repetitive motor training significantly enhances upper limb motor recovery in subacute stroke. These findings support cerebellar neuromodulation as a promising adjunct in post-stroke rehabilitation.