UT Southwestern Medical Center will be one of three national sites to pioneer U.S. testing for an implant device that stimulates the vagus nerve in stroke patients to see whether it can help restore lost arm function.
The Vivistim® System device, developed by Dallas-based MicroTransponder Inc. with a license from UT Dallas, stimulates the neck's vagus nerve, a key nerve stretching from the medulla oblongata in the brain down to the throat, larynx, trachea, lungs, heart, esophagus, and intestinal tract. Implanted under the collarbone, the device, which is about the size of a pacemaker, sends painless, half-second electrical pulses up the vagus nerve, causing chemicals called neuromodulators to be released in various parts of the brain. Alternate forms of vagus nerve stimulation therapy already are approved for use in the U.S. by the Federal Drug Administration for treating other illnesses, including depression and epilepsy.
"These neuromodulators appear to facilitate the creation of new neuron pathways in the brain, which play a key role in restoring muscle movement," said Dr. Ty Shang, Assistant Professor of Neurology and Neurotherapeutics at UT Southwestern, who is heading the UT Southwestern arm of the trial. UT Southwestern is one of three sites in the nation.
"A stroke deprives brain cells of oxygen," said Dr. Shang, a vascular neurologist who is part of UT Southwestern's stroke team. "Without oxygen, the brain cells die, and can no longer perform the function for which they were intended. There has been no known way to regenerate new brain cells to replace them, but in early tests with this device, the brain appears to 'rewire' other cells to perform the function.
The study is sponsored by MicroTransponder Inc. and partially funded by the Texas Biomedical Device Center at UT Dallas. The Vivistim® system, designed to improve motor function in the more involved arm of a person following stroke, was studied starting in 2013 for efficacy and safety in a small study in Glasgow, Scotland. Individuals in the Glasgow study experienced meaningful functional improvements in their more involved arm. Many were able to resume daily activities like swimming, driving, and caring for grandchildren.
"VNS therapy may be the stimulus for motor relearning with the more involved arm for individuals following stroke. Gaining functional improvement in the impaired arm is an arduous task. VNS therapy might make achieving functional gains easier," Dr. Shang said.
UT Southwestern researchers are seeking persons in the Dallas-Fort Worth metroplex who had a stroke four months to five years ago to participate in the trial. After having outpatient surgery to implant the device, participants will be scheduled for 18, 90-minute sessions of intensive, task-specific therapy over a six-week period with quarterly follow-up evaluations for the next year.
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