Effects of transcutaneous electrical nerve stimulation on cognitive function and upper limb motor function in people with chronic stroke: a randomized controlled trial

Transcutaneous electrical nerve stimulation, including transcutaneous vagus nerve stimulation (tVNS) and transcutaneous spinal cord stimulation (tSCS), is potential interventions that can alleviate cognitive decline and promote motor recovery by modulating neurotransmitter systems, but current evidence in people with stroke remains inconclusive. This study investigated the effects of tVNS and tSCS and compared their efficacy in improving cognitive function and upper limb motor function after stroke. In this randomized controlled trial, 90 people with chronic stroke (mean ± standard deviation: 65.12 ± 5.85 years of age) were randomly assigned to receive 18 sessions of either tVNS, tSCS, or sham stimulation, each delivered concurrently with upper limb exercises for 45 min, three times per week, for 6 weeks. The primary outcomes were the Montreal Cognitive Assessment (MoCA) and the Fugl-Meyer Assessment for Upper Extremity (FMAUE). Outcomes were measured at baseline, after 9 and 18 sessions, and at 1 month after the intervention. The tVNS and tSCS groups demonstrated significantly greater improvements than did the sham group in MoCA (mean differences, 2.37 and 1.77, respectively; p < 0.001) and FMAUE scores (mean differences, 3.37 and 2.10, respectively; p < 0.001 and p = 0.007, respectively) after the intervention. Improvements in cognition persisted for 1 month in both groups, as indicated by non-significant within-group changes from post-intervention to follow-up assessments, whereas motor improvements were sustained only in the tVNS group. Both tVNS and tSCS may be potential interventions to combine with exercise for improving cognitive and upper limb function after stroke. ClinicalTrials.gov: NCT05615610.