“Vagus” is Latin for “wandering,” and it aptly describes the cranial nerve that runs all the way from the brain stem down to the colon. The vagus nerve is a sensory nerve, but it is also involved in motor function.
Electrical stimulation of the vagus nerve is a common treatment for epilepsy.
In VNS, surgeons implant in the chest a pacemaker-like electrical pulse generator with a wire connected to the left vagus nerve. The generator stimulates the nerve with pulses of electric current, pausing periodically to let the nerve rest. The current passes through the vagus nerve to the brain.
The USC team’s multi-clinical, international research involved 108 participants, each of whom was experiencing moderate to severe arm weakness over a period of 9 months to 10 years after a stroke event. The study was randomized and triple-blind.
The researchers surgically implanted VNS devices in all participants. Of them, 53 received VNS treatment designed to stimulate the organizational potential of the brain. For the remaining 55 participants, the implanted device was never activated — it served as a placebo for this control group.
After implantation and either actual or sham VNS, all individuals were given 6 weeks of in-clinic physical therapy aimed at regaining arm function.
This intensive therapy included six types of tasks:
reaching and grasping
simulated eating tasks
opening and closing containers
After the 6 weeks, people continued working on arm function with prescribed daily home exercises.
After the rehabilitation period, the authors of the study tested the participants’ arm function.
They write, “[P]articipants who were assigned to [VNS] paired with rehabilitation showed clinically meaningful improvements in motor impairment and function compared with participants assigned to rehabilitation and sham stimulation.”
Twice the number of people in the VNS group showed improvement in arm function compared with those in the control group at day 90 after completion of in-clinic therapy.
Nearly half the VNS group showed significant improvement.
Dr. Liu noted, “Not only were the results clinically meaningful, the fact that these patients were at least 9 months post-stroke, and in some instances years out, points to the possibility that meaningful improvements can be achieved even years after a stroke.”
The researchers plan for a long-term outcomes companion paper to assess the permanence of the arm movement gains.
In addition, the study explored the effects of just a limited course of combined VNS and rehabilitation. Dr. Liu told Medical News Today that “there is no reason to believe that additional sessions, that is, at home, would not result in further improvements. However, undoubtedly, every treatment paradigm will eventually reach a plateau.”
The researchers suspect VNS triggers the release of brain neuromodulators to strengthen the brain’s motor circuits, restoring their ability to relearn movement.
“For too long,” Dr. Liu explained, “stroke patients have faced limited options for recovery. This new treatment signifies a breakthrough that could be life-changing for many stroke patients and also represents an approach that will certainly be explored for many other functional restoration applications in the future.”
When asked whether the study’s findings suggest other possible applications for VNS, Dr. Liu replied:
“Absolutely! In my view, the nervous system has three broad categories of phenotypes: sensorimotor, cognitive, and autonomically controlled. In each of them, we have every reason to believe that the correct combination of the right kind of neuromodulation and task-specific practice will result in better outcomes.”
He went on to say, “Almost immediately, it would most certainly be reasonable to combine VNS with other types of rehabilitation therapies for other indications.“
Others are already in the process of exploring these possibilities, he added.