- Each year, almost 800,000 people in the United States have a stroke.
- In many, this causes long-term disability and issues with the mobility of one or more limbs.
- One common result of a stroke is the lasting inability to use an arm and hand.
- Researchers have helped restore arm and hand movement in two individuals who experienced complete arm immobility following a severe stroke.
- The researchers restored movement in the limbs by using electrical stimulation of the spinal cord.
Stroke is a leading cause of death in Americans and, according to the Centers for Disease Control and Prevention (CDC), around 795,000 people in the United States will experience a stroke each year.
With improvements in treatments, the chance of surviving a stroke is increasing, particularly for younger people.
However, because stroke rates are increasing in people aged under 55 years, more people are likely to be left with a long-term disability, so rehabilitation after a stroke is increasingly important.
One common result of a stroke is arm stiffness, weakness, and immobility. In many people, this resolves within around 6 months, but if it persists beyond this point, they may struggle to regain full function of the arm.
Current therapies are based predominantly on physiotherapy, exercise, and task-specific training, but these are frequently ineffective in those with significant arm weakness.
Now, scientists from the University of Pittsburgh and Carnegie Mellon University have restored arm mobility in two stroke survivors using electrical stimulation of the spinal cord in the cervical (neck) area.
The findings are published in Nature Medicine.
American Heart Association volunteer Prof. Daniel T. Lackland, a professor in the department of neurology at the Medical University of South Carolina, not involved in this research, told Medical News Today:
“These are important findings from a seasoned team of investigators and a first investigation in humans using a novel electrical stimulation of cervical spinal circuits to facilitate arm and hand motor control in chronic post-stroke hemiparesis. From a ‘study design’ consideration, it must be noted these results are very preliminary and based on a select sample of two people.”
Both participants had extensive damage to the cortico-spinal tract (CST), which resulted in lasting impairment to their arms and hands.
The researchers implanted two linear electrodes in the neck to span the dorsal roots of the spinal cord from the fourth cervical vertebra down to the first thoracic vertebra.
The electrodes stimulated the CST, allowing impulses to be sent down the arm.
“After a stroke, many people have damage to the part of their brain that controls movement, so the signal the brain sends to the spinal cord is weak,” explained Dr. Ania Busza, assistant professor of neurology, neurosurgery, physical medicine and rehabilitation, and neuroscience at the University of Rochester Medical Center. Dr. Busza was not involved in this study.
“This implanted spinal stimulation seems to be able to amplify the spine’s response to the weaker signals sent from the brain, allowing the person to achieve bigger movements,” she added.
Four days after implanting the electrodes, the researchers began the stimulation of the spinal cord. They then assessed the participants five times a week for 4 weeks.
Dr. Charles Liu, director of the USC Neurorestoration Center and neurosurgeon with Keck Medicine of USC, who has investigated stimulating the vagus nerve to restore arm movement in stroke survivors, welcomed the study, telling MNT:
“In general, the spinal cord has received far less attention in the neuromodulation/ stimulation compared to the brain, other than for indications related to pain. There has been long reported evidence that the spinal cord stimulation/ modulation could be very important for neurorestoration, including in humans — mainly with spinal cord injury.”
During spinal cord stimulation (SCS), both participants regained some movement of their arms and hands. The researchers report that “SCS led to immediate and substantial improvements in strength and muscle activity of the arm and hand.”
They were also able to perform reaching tasks — stretching out to reach targets horizontally in front of them — that they could not do without stimulation. The researchers noted that stimulation increased the activity of muscles around the elbow, allowing the participants to stretch out their arms.
One participant, whose impairment was less severe, was then given some everyday tasks to do.
With stimulation, the woman was able to grasp and lift a tin of soup, use a key to open a lock, and even feed herself with the affected hand, something she had been unable to do for the 9 years since her stroke.
The participants’ Fugl-Meyer scores, which assess limb motor impairment, improved markedly over the 4 weeks of stimulation, with the first participant improving from 35 points to 47 points, and the second participant from 15 to 18 points.
To the researchers’ surprise, these improvements were maintained 4 weeks after SCS was stopped and the implants removed.
Dr. Busza told MNT that this finding was particularly encouraging: “It’s very exciting that some of the effects seem to last after the electrical stimulator is removed! But we need more research to understand why — one (less exciting) possibility is that after using the weaker arm more for a month, the person’s muscles got stronger and this led to them being able to do more with it even after the stimulation was removed.”
“A more exciting possibility is that the intervention caused people to use/ notice/ think about their affected arm more, and that this then caused new connections/ plasticity in the brain’s motor systems. We’ll have to see what they find with future studies,” she added.
This treatment enabled the participants to move their hands and arms in ways that they had been unable to for some years without stimulation.
The findings could give hope to the many people left with mobility issues following strokes. However, they must be backed up by further research, as Prof. Lackland told us.
“Motor deficits of the arms and hands after cerebral strokes remain a major issue, with novel neurotechnology and rehabilitation intervention being developed. For the stroke patient and caregivers, this study of ‘epidural spinal cord stimulation with protocol-based upper-limb rehabilitation’ provides an encouraging mode that can be further studied and developed for implementation,” he said.
Dr. Liu agreed, nevertheless cautioning that the findings were just a start: “I have no doubt that the combination of neuromodulation and task-specific-practice will change the potential of rehabilitation in the future, including combinations of brain, spinal cord, and cranial/ peripheral nerve techniques. While there remains much work to be done before stroke patients can consider this a viable option, the potential is certainly compelling.”
It may be early days, but developments in spinal cord stimulation could well lead to effective therapies for the many people whose mobility is affected by stroke.