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Spinal stimulation ‘improves arm function after stroke’

Survivors could regain movement in their hand which had previously been lost for years, research shows

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Neurotechnology that stimulates the spinal cord can instantly improve arm and hand mobility, enabling people affected by moderate to severe stroke to conduct their normal daily activities more easily, new research has revealed.

Through implanting a pair of thing metal electrodes along the next to engage intact neural circuits, stroke patients were enabled to fully open and close their fist, lift their arm above their head or use a knife and fork to cut up food after years of being unable to do so. 

The study, from the University of Pittsburgh and Carnegie Mellon University, gives new hope around long-term paralysis and mobility problems post-stroke.

“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 Dr Marco Capogrosso, assistant professor of neurological surgery at Pitt.

“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 pre-clinical 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.”

Globally, one in four adults over the age of 25 will experience stroke in their lifetime, and 75 per cent of those people will have lasting deficits in motor control of their arm and hand, which can severely limit their physical autonomy and exacerbate loneliness and isolation. 

Currently, no treatments are effective for treating paralysis in the 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 neuro-rehabilitation solutions for people affected by movement impairment after stroke is becoming ever more urgent,” said senior co-author Dr 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.”

Spinal cord stimulation technology uses a set of electrodes placed on the surface of the spinal cord to deliver pulses of electricity that activate nerve cells inside the spinal cord. This technology is already being used to treat high-grade, persistent pain. 

Additionally, multiple research groups around the world have shown that spinal cord stimulation can be used to restore movement to the legs after spinal cord injury.

But the unique dexterity of the human hand, combined with the wide range of motion of the arm at the shoulder and the complexity of the neural signals controlling the arm and hand, add a significantly greater set of challenges.

Following years of extensive pre-clinical studies involving computer modelling and animal testing in macaque monkeys with partial arm paralysis, researchers were cleared to test this optimised 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 Dr Douglas Weber, professor of mechanical engineering at the Neuroscience Institute at Carnegie Mellon University. 

“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.

Moving forward, researchers continue to enrol additional trial participants to understand which stroke patients can benefit most from this therapy and how to optimise stimulation protocols for different severity levels.

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