Many of those who have suffered a stroke experience long term weakness that can affect their quality of life. Commonly, loss of arm function affects the ability to perform daily tasks including preparing food, dressing, and carrying objects. At this time, there are still very few effective rehabilitation interventions addressing arm impairment after stroke. One potential method to improve arm function is by reorganizing connections in the brain, which may be facilitated through vagus nerve stimulation (VNS). When the vagus nerve is stimulated, the brain releases neuromodulators that play a key role in facilitating neuroplasticity, or the brain’s ability to form new connections and pathways between neurons.
MicroTransponder, a medical device company, has sponsored a pivotal randomized controlled stroke rehabilitation trial investigating the effectiveness of VNS paired with upper limb rehabilitation to treat arm and hand weakness following a stroke. The results of this study have shown that patients who received VNS in combination with upper-limb-focused therapy exhibited clinically meaningful improvements with regard to arm motor impairment and function.
The Brain Recovery Lab, led by Teresa Kimberley, PT, PhD, FAPTA, was one of 19 sites conducting this study across the United States and the United Kingdom, enrolling a total of 108 participants. Subjects were randomly divided into an experimental and control group. The experimental group received rehabilitation paired with active VNS and the control group received rehabilitation paired with sham VNS. All subjects underwent VNS device implantation via a surgical procedure. In-clinic rehabilitation began approximately one week after the VNS device was implanted and consisted of 1.5-hour-long sessions occurring 3 times per week for 6 weeks. Therapy involved intensive, task-based, individualized arm exercises. All exercises were tailored to the subjects’ functional level and adjusted to provide adequate difficulty and facilitate progress. During all exercises, therapists triggered the VNS device during key points in task-specific therapeutic movements.
After the 6 week in-clinic rehabilitation was completed, subjects began a 30-minute, daily home exercise program prescribed by their therapist. The home exercises included tasks similar to those performed during in-clinic treatment. Therapists followed up bi-weekly with subjects to ensure home based tasks continued to provide an adequate challenge, adjusted tasks as needed, and discussed any compliance concerns. Three months after the start of home-based therapy, subjects originally randomized to the sham VNS group, crossed over to receive an additional 6 weeks of in-clinic rehabilitation paired with active VNS.
The primary outcome was the change in the Upper Extremity Fugl-Meyer Assessment (FMA-UE) score, an industry standard used to assess upper limb impairment after stroke. After 6 weeks of in clinic therapy, FMA-UE score increased by 5.0 ± 4.4 points in subjects receiving active-VNS compared to 2.4 ± 3.8 points in Controls (p=0.001). After 3 months of home-therapy, 47% of the subjects in the active-VNS group showed a clinically meaningful response (≥ 6-point change) on the FMA-UE compared to 24% in the sham VNS group (p=0.01). Subjects receiving active-VNS also showed a 2-3 times greater improvement compared to the sham-VNS group in self-assessment of their own well-being, noting improvements in quality-of-life domains including Activities of Daily Living and Self-Care. Once subjects in the sham-VNS group crossed over to receive active-VNS, motor gains were similar to the gains observed in the original active-VNS group. Preliminary results show that FMA-UE and WMFT scores were maintained at 6 months and one-year post-therapy.
Conclusions of the study suggest that paired VNS and rehabilitation may be a new useful tool for stroke recovery. The VNS device is currently being reviewed by the FDA for approval for use in the US.