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Neuro Stimulation Reduces Stroke Muscle Weakness



13 Aug. 2019. A clinical trial shows a non-invasive device stimulating the spinal cord and upper limb muscles reduces spasticity and muscle weakness in people who suffered a stroke. Results from the trial appear in the 23 July issue of the journal Bioelectric Medicine.

The trial is testing the Myoregulator system made by PathMaker Neurosystems Inc. in Boston and Paris for reducing muscle spasticity and muscle weakness in people who experience a stroke. In neuromotor spasticity muscles are continuously contracted, which interferes with normal speech and movements. The condition, marked by muscle tightness and involuntary movements, is a symptom of stroke, but also other neuromuscular disorders including cerebral palsy, multiple sclerosis, and spinal cord injury.

The Myoregulator system simultaneously stimulates nerve pathways in the spinal cord and peripheral nerves in the affected limbs. Electrodes are placed on the skin on two sides of the spinal cord — usually back and abdomen — sending an electric current through the spinal cord, a process called trans-spinal direct current stimulation. At the same time, the Myoregulator attaches electrodes on the skin over muscles in the arms and wrist experiencing spasticity and muscle weakness, a technique called peripheral nerve direct current stimulation. Nerve stimulation sessions last for about 20 minutes.

The clinical trial enrolled 26 individuals at the Feinstein Institute for Medical Research in Manhasset, New York who suffered a stroke and are experiencing hand and wrist spasticity. Participants received 20-minute nerve stimulation sessions once a day for 5 consecutive days, first with a sham device, then with a working MyoRegulator system, separated by a one week wash-out period. Participants — who were not told which were the sham and real sessions — were rated on days 3 and 5, on measures of muscle resistance and a standard scale of spasticity, after both the sham and real nerve stimulation sessions, then after 5 weeks.

The results show the 20 participants completing the program experienced less muscle resistance and spasticity at the end of the MyoRegulator sessions compared to the sham stimulation. And the reduced muscle resistance and spasticity measures persisted for 5 weeks following the last real stimulation treatment.

The research team also rated participants on standard scales of motor functions after a stroke, Fugl-Meyer Assessment and Wolf Motor Function Test. Individuals in the trial completing the full stimulation program and follow-up evaluations, 16 of the original 26 participants, were rated on these measures. The results show by the follow-up evaluations, participants improved their upper-limb motor functions in addition to reducing spasticity and weakness. Stroke patients, say the researchers, usually require specialized rehabilitation training to achieve these results.

Bruce Volpe, a professor in the Feinstein Institute’s molecular medicine department and principle investigator on the project, says in an institute statement, “The surprise in these clinical results were the improved motor functions that apparently occurred with the focused treatment only of spasticity. We are eager to start a trial that couples motor training and anti-spasticity treatment.”

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