according to preliminary results of a randomized clinical trial at the 2021 annual meeting of the American Academy of Neurology.
Dr. Jesse Dawson
“We believe that vagus nerve stimulation combined with rehabilitation is an acceptable and effective intervention for improving upper-limb impairment and function in people with moderate to severe arm weakness a long time VNS-REHAB pivotal study is a randomized, blinded, controlled trial of 108 people who had upper-extremity weakness after having a stroke at least 9 months before enrollment. The average for the group was 3 years post stroke after ischemic stroke,” said Jesse Dawson, MD, a professor at the University of Glasgow.
The Fifty-three patients were assigned active VNS followed by 6 weeks of in-clinic rehabilitation and then 90 days of home-based rehab. At in-clinic rehab, the therapist initiated a 5-second burst of VNS stimulation during each movement. In home-base treatment, the device was activated by a magnet.
Fifty-five patients were assigned sham VNS. After 90 days, the sham group crossed over to receive VNS for 6 weeks and then 90 days of home exercise. This crossover group was the focus of the data Dr. Dawson presented at AAN 2021. The overall trial results have been published in the Lancet.
“The hypothesis is based on the knowledge that the VNS stimulates the release of proneuroplastic neuromodulators norepinephrine and acetylcholine,” Dr. Dawson said. “By pairing VNS with task-specific movement, we hypothesize that we will increase task-specific neuroplasticity.”
The main study showed “a statistically significant difference across all primary and secondary endpoints at all time points in favor of rehabilitation paired with VNS,” Dr. Dawson said. The primary outcome was improvement in Fugl-Meyer Upper Extremity (FMA-UE) outcome, with the active VNS group having a significantly higher percentage of responders. For example, 47% of the active VNS patients had a greater than 6-point response on FMA-UE improvement versus 27% of the sham group (P = .010).
When the sham group crossed over to active VNS, the improvement in arm function matched that of the treatment group in the main study, Dr. Dawson said. “If you look at specifically what happened after they completed the control phase, there was a further small increase in Fugl-Meyer score, but, more importantly between 20% and 35% achieved a clinically important response on the Fugl-Meyer assessment or the Wolf Motor Function Test, giving a number need to treat ranging from three to five,” he said.
Dr. Dawson said that data on adverse events was presented in the Lancet publication. “These were observed at expected frequencies,” he said.
In an interview, he explained the significance of reporting the number to treat. “The number needed to treat helps give an idea of how many times you need to do something to achieve the desired outcome. So for VNS paired with rehab versus rehab alone, you need to treat four people to get one extra clinically important response, compared with just doing therapy.”
The next steps for his group’s research, he said, “will be to try and explore whether we can predict who responds best, and we would like to see if people with other types of stroke benefit.”
Dr. Andreas Luft
In providing comment on the study, Andreas Luft, MD, a professor at the University Hospital Zürich, noted that the FME-UE score improvements reported “are significant and meaningful. ... However, they may also be achieved by increasing the intensity of training. Many medical systems offer their patients high rehabilitation intensities and achieve similar improvements. Whether VNS can further boost higher-intensity training ‘beyond its limits’ is probable but remains to be demonstrated.”
Dr. Luft noted the study advances the knowledge of combining a therapeutic approach with training. “More such approaches are necessary to increase the therapeutic instrumentation of neurorehabilitation,” he said.
Dr. Dawson reported a financial relationship with MicroTransponder. His coauthors reported relationships with MicroTransponder, SanBio, Fujifilm Toyoma Chemical, Medtronic, TRCare, SAEBO, Allergan/AbbVie, Ipsen, Merz, Ottobock/Hangar Orthopedics, Parker Hannifin, Revance Therapeutics, ReWallk, and Sword Health. Three coauthors are employees of MicroTransponder. Dr. Luft has no relevant relationships to disclose.