Effects of Cerebellar Transcranial Direct Current Stimulation on Improving Post-Stroke Upper Extremity Motor Function: A Protocol for a Randomized Controlled Clinical Trial

Ziqiao Huang¹Jiahao Lao¹Zhibin Chen¹Yuxuan Wu¹Bo Tang¹Wei Liao¹Wanqi Jiang¹Junjie Liang¹Zirui Luo^1*Haian Mao^1,2*

• ¹The Fifth Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
• ²Department of Rehabilitation Medicine, Neurosurgery Department, the Fifth Affiliated Hospital of Guangzhou Medical University, Guangzhou, China

Abstract Background: Upper extremity motor impairment is a prevalent and disabling consequence of stroke. While conventional rehabilitation improves function, recovery often plateaus. Cerebellar transcranial direct current stimulation (c-tDCS) presents a promising neuromodulatory adjunct by targeting cerebellar involvement in motor coordination, timing, and learning. However, robust evidence from well-designed randomized controlled trials (RCTs) is needed to establish its efficacy in enhancing post-stroke upper limb recovery. Objective: This RCT protocol aims to evaluate the efficacy of anodal c-tDCS applied concurrently with conventional upper limb rehabilitation (CULR), compared to sham stimulation plus the same rehabilitation, on improving motor function of the paretic upper extremity in subacute/chronic stroke patients. Methods: A double-blind, randomized, sham-controlled trial will be conducted. Fourty-eight participants with unilateral stroke and moderate to severe upper limb motor impairment will be randomized to either active or sham group. Anodal tDCS will be conducted to the ipsilesional cerebellar hemisphere in the active group, while sham delivery will be performed in the sham group. Both groups receive CULR after each c-tDCS session. Multimodal assessments will be administered pre-and post-intervention, comprising: Fugl-Meyer assessment upper extremity (FMA-UE) for motor impairment quantification, fNIRS capturing resting-state and c-tDCS-induced cortical hemodynamic responses and transcranial magnetic stimulation-derived motor evoked potentials (TMS-MEPs) evaluating cortical excitability. Conclusion: This rigorously designed RCT will provide high-level evidence on the therapeutic potential of c-tDCS as an adjunct to rehabilitation for improving upper limb motor function post-stroke. Findings will inform clinical practice regarding novel neuromodulation strategies to augment recovery. Clinical trial registration: https://www.chictr.org.cn, identifier ChiCTR2500101094