Non-invasive Brain Stimulation Techniques for the Improvement of Upper Limb Motor Function and Performance in Activities of Daily Living After Stroke: A Systematic Review and Network Meta-analysis.

OBJECTIVE: To compare the efficacy of non-invasive brain stimulation (NiBS) such as transcranial direct current stimulation (tDCS), repetitive transcranial magnetic stimulation (rTMS), theta-burst stimulation (TBS), and transcutaneous vagus nerve stimulation (taVNS) in upper limb stroke rehabilitation.

DATA SOURCES: PubMed, Web of Science, and Cochrane databases were searched from January 2010 to June 2022.

DATA SELECTION: Randomized controlled trials (RCTs) assessing the effects of "tDCS", "rTMS", "TBS", or "taVNS" on upper limb motor function and performance in activities of daily livings (ADLs) after stroke.

DATA EXTRACTION: Data were extracted by 2 independent reviewers. Risk of bias was evaluated with the Cochrane Risk of Bias tool.

DATA SYNTHESIS: 87 RCTs with 3750 participants were included. Pairwise meta-analysis showed that all NiBS except continuous TBS (cTBS) and cathodal tDCS were significantly more efficacious than sham stimulation for motor function (standardized mean difference [SMD] range 0.42-1.20), whereas taVNS, anodal tDCS, and both low and high frequency rTMS were significantly more efficacious than sham stimulation for ADLs (SMD range 0.54-0.99). NMA showed that taVNS was more effective than cTBS (SMD:1.00; 95% CI (0.02-2.02)), cathodal tDCS (SMD:1.07; 95% CI (0.21-1.92)), and Physical rehabilitation alone (SMD:1.46; 95% CI (0.59-2.33)) for improving motor function. P-score found that taVNS is best ranked treatment in improving motor function (SMD: 1.20; 95% CI (0.46-1.95)) and ADLs (SMD:1.20; 95% CI (0.45-1.94)) after stroke. After taVNS, excitatory stimulation protocols (intermittent TBS, anodal tDCS, and HF-rTMS) are most effective in improving motor function and ADLs after acute/sub-acute (SMD range 0.53-1.63) and chronic stroke (SMD range 0.39-1.16).

CONCLUSIONS: Evidence suggests that excitatory stimulation protocols are the most promising intervention in improving upper limb motor function and performance in ADLs. taVNS appeared to be a promising intervention for stroke patients, but further large RCTs are required to confirm its relative superiority.