Effects of transcutaneous auricular vagus nerve stimulation added to robotic rehabilitation in patients with ischemic stroke: a randomized clinical trial

Background This study aimed to investigate the effects of adding transcutaneous auricular vagus nerve stimulation (taVNS) to robotic rehabilitation on functional outcomes and neuromuscular activity in patients with ischemic stroke. Methods This randomized controlled clinical trial employed a pre-post study design and was conducted in a hospital-based physiotherapy and rehabilitation clinic. A total of 40 patients with ischemic stroke, aged 18-65 years, were randomly assigned to either a robotic rehabilitation group (RRG) or a combined vagus nerve stimulation and robotic rehabilitation group (VRRG). Spasticity, walking speed, motor function, quality of life, muscle activity, and pain were assessed at baseline and after six weeks of treatment. Results Primary outcome measures were walking speed, motor function assessed by the Fugl-Meyer Assessment, and pain intensity. Secondary outcomes included electrophysiological measurements (H-reflex and F-wave parameters) and quality of life. Within-group analyses showed significant improvements in all outcomes in the VRRG (p < 0.05), whereas all outcomes except pain improved significantly in the RRG (p < 0.05). Between-group comparisons demonstrated greater improvements in walking speed in the VRRG compared with the RRG (mean difference - 1.84 s, 95% CI - 3.7 to - 0.7; r = 0.43; p = 0.006) and greater pain reduction in the VRRG (mean difference - 1.55, 95% CI - 2.5 to - 0.1; r = 0.30; p = 0.048). In contrast, a greater reduction in the Hmax/Mmax amplitude ratio-an electrophysiological marker of spinal excitability-was observed in the RRG. Conclusion The findings suggest that transcutaneous auricular vagus nerve stimulation combined with robotic rehabilitation may provide additional benefits in terms of walking speed and pain reduction in patients with ischemic stroke.