by Amy Norton
WEDNESDAY, November 9, 2022 (HealthDay News) — In an advance in treating spinal cord injuries, researchers have identified neurons that are key to allowing paralyzed people to walk again.
The results came, in part, from nine patients who participated in an ongoing Swiss study seeking to restore mobility to people with paralysis.
The nine quickly regained the ability to stand and walk with the help of implants that electrically stimulate the spinal nerves that control movement in the lower body.
The researchers now report that they have identified a specific group of cells in the lower part of the spine that appears to be essential for restoring movement.
The hope is that the discovery will help improve electrical stimulation therapy — and eventually help develop more sophisticated ways to restore the complex movement of people with paralysis, experts said.
In the United States alone, as many as 450,000 people live with a spinal cord injury, according to the American Society of Neurological Surgeons. Just over half of these injuries happen to people under the age of 30, the majority of whom are male – traffic accidents or violence are often to blame.
Spinal cord injuries primarily cut off the connection between the brain and spinal nerves below the level of the injury.
But these neurons are not useless – just offline. For years, researchers have been studying epidural electrical stimulation (EES) as a way to fire those neurons and restore some measure of movement to paralyzed people.
EES involves implanting electrodes that deliver electrical currents to nerve cells in the spinal cord. The electrodes are connected to a pulse generator implanted in the abdomen.
Iman Azim, a researcher at the Salk Institute in La Jolla, California, who studies the mechanisms behind human movement, said the history of EES’s use stretches back 50 years as a treatment for pain.
Along the way, researchers realized that EES also affects movement. Over the past decade or so, various research teams have used EES, along with intensive physical rehabilitation, to help a small number of paralyzed people regain the ability to stand and walk to some extent.
Azim said the Swiss team had made “big leaps” in developing their approach in recent years.
They have developed, for example, electrodes that precisely target the “dorsal root” areas of the spinal cord that control leg and trunk movement. They’ve also incorporated cutting-edge technology that stimulates nerves in a pattern that better mimics the way the brain performs a task.
The team, from the Swiss Federal Institute of Technology and the University of Lausanne, reported their three most recent patients earlier this year. The patients, all men between the ages of 29 and 41, had spinal cord injuries that left them without sensation or movement in the legs.
They all underwent surgery in 2020 to implant EES devices. The implants were paired with software that allows patients and physiotherapists to set up semi-automated stimulation programs that allow a variety of movements. People can run these programs themselves, via a tablet and small remote controls that connect wirelessly to the pulse generator.
These three patients were able to stand and walk with support immediately upon recovery from surgery.
The Swiss team discovered something particularly interesting along the way: some of the nine patients were able to walk even with the electrical stimulation turned off — indicating, Azim said, a “reorganization” of neurons involved in walking.
To dig deeper, the researchers turned to lab mice to mimic several key features of EES in humans with spinal cord injuries. They were able to focus on a group of neurons – called Vsx2 neurons – that appear to be “essential” for restoring walking with EES.
‘Silencing’ neurons prevented lab mice from regaining their ability to walk using EES; Activation of neurons restored their movement.
“This study wondered, What happens in the spinal cord during stimulation?” He said great. “This is a big black box.”
Dr. Greg Nemonitis, director of spinal cord injury rehabilitation at Cleveland Clinic in Ohio, described the restored function in these nine patients as “fantastic.”
He also said that the discovery of “healing-regulating neurons” while mice were “a first step in understanding and enhancing function in humans until a ‘cure’ is found.”
Azim said that in the short term, the results on these key neurons could help further improve EES.
Looking to the future, he said, a greater understanding of how EES promotes movement recovery could help develop more complex treatments. Azim noted that technologies are advancing to the point that eventually it may be possible to safely access the spinal cord and “reconstruct” damaged circuits.
He said, “This is not a false dream.”
The results were published online November 9 in the journal temper nature.
The US National Institute of Neurological Disorders and Stroke provides an overview of spinal cord injury.
SOURCES: Iman Azim, Ph.D., associate professor, Salk Institute for Biological Studies, La Jolla, CA; Greg Nemonitis, MD, director, Spinal Cord Injury Rehabilitation, Cleveland Clinic, and Professor, Case Western Reserve University School of Medicine, Cleveland, Ohio; temper nature, November 9, 2022, online
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