March 2023 issue
March 31, 2023 | A team of investigators from two Pittsburgh research institutions and a startup firm have developed a novel neurorehabilitation technology that may soon add to clinicians repertoire for treating stroke. While previous efforts at stroke rehabilitation have used vagus nerve stimulation, cortical stimulation, and surface stimulation strategies, the new approach uses spinal cord stimulation to improve arm and hand mobility.
Researchers from the University of Pittsburgh and Carnegie Mellon University reported in Nature Medicine that people affected by moderate to severe stroke can conduct normal daily activities more easily as a result of the new therapy. Marc Powell, founder of a startup called Reach Neuro, was first author of the paper, along with Nikhil Verma of CMU and Erynn Sorensen of Pitt.
The team implanted a pair of metal electrodes along the neck engage intact neural circuits, allowing stroke patients to fully open and close their fist, lift their arm above their head or use a fork and knife to cut a piece of steak for the first time in years.
“We discovered that electrical stimulation of specific spinal cord regions enables patients to move their arm in ways that they are not able to do without the stimulation,” said Marco Capogrosso, assistant professor of neurological surgery at Pitt and a co-author of the paper. “Perhaps even more interesting, we found that after a few weeks of use, some of these improvements endure when the stimulation is switched off, indicating exciting avenues for the future of stroke therapies.”
“Thanks to years of preclinical research building up to this point, we have developed a practical, easy-to-use stimulation protocol adapting existing FDA-approved clinical technologies that could be easily translated to the hospital and quickly moved from the lab to the clinic.”
Currently, no treatments are effective for treating paralysis in the so-called chronic stage of stroke, which begins approximately six months after the stroke incident. The new technology, researchers say, has the potential to offer hope for people living with impairments that would otherwise be considered permanent.
“Creating effective neurorehabilitation solutions for people affected by movement impairment after stroke is becoming ever more urgent,” said senior co-author Elvira Pirondini, assistant professor of physical medicine and rehabilitation at Pitt. “Even mild deficits resulting from a stroke can isolate people from social and professional lives and become very debilitating, with motor impairments in the arm and hand being especially taxing and impeding simple daily activities, such as writing, eating and getting dressed.”
Following years of extensive preclinical studies involving computer modeling and animal testing in macaque monkeys with partial arm paralysis, researchers were cleared to test the new therapy in humans.
“The sensory nerves from the arm and hand send signals to motor neurons in the spinal cord that control the muscles of the limb,” said co-senior author Douglas Weber, professor of mechanical engineering at the Neuroscience Institute at CMU. “By stimulating these sensory nerves, we can amplify the activity of muscles that have been weakened by stroke. Importantly, the patient retains full control of their movements: The stimulation is assistive and strengthens muscle activation only when patients are trying to move.”
In a series of tests adapted to individual patients, stimulation enabled participants to perform tasks of different complexity, from moving a hollow metal cylinder to grasping common household objects, such as a can of soup, and opening a lock. Clinical assessments showed that stimulation targeting cervical nerve roots immediately improves strength, range of movement and function of the arm and hand.
Unexpectedly, the effects of stimulation seem to be longer-lasting than scientists originally thought and persisted even after the device was removed, suggesting it could be used both as an assistive and a restorative method for upper limb recovery. Indeed, the immediate effects of the stimulation enable administration of intense physical training that, in turn, could lead to even stronger long-term improvements in the absence of the stimulation.
“When the stimulation is on, I feel like I now have control of my arm and my hand again that I haven’t had in over nine years,” said Heather Rendulic, a clinical trial participant who suffered a stroke in 2012.
Moving forward, researchers continue to enroll additional trial participants to understand which stroke patients can benefit most from this therapy and how to optimize stimulation protocols for different severity levels.
