Hexbyte – Tech News – Ars Technica |
“It’s an amazing feeling,” says David Mzee, whose left leg was paralyzed in 2010. Mzee has now regained some ability to walk thanks to a breakthrough in spinal-cord stimulation technology. “I can do a knee extension of my left leg… flex my hip and even move my toes.”
Mzee is one of three participants in a study that used a new technique to overcome spinal-cord injury and restore walking ability in patients with varying degrees of paralysis. The results, published in Nature and Nature Neuroscience today, are dramatic. All three patients recovered some degree of walking ability, and their progress in physical-therapy sessions has translated to improved mobility in their daily lives.
The basis of the technique, called epidural electrical stimulation (EES), is not new at all—it’s been investigated as a potential treatment for paralysis for decades, with a lot of success in animals. And in September this year, two separate papers reported breakthroughs in allowing patients with paralysis to walk, with assistance, as a result of EES.
But the earlier patients made progress only after months of intensive rehabilitation—in the best case, after four months, and in others, closer to a year. What Grégoire Courtine, Jocelyne Bloch, and a large team of researchers report today is a huge leap forward: their patients were able to walk (with assistance) after only a few days.
Hexbyte – Tech News – Ars Technica | Blocking the feedback loop
The difference lies in how constant the electrical stimulation is. EES works by implanting a device that delivers electrical signals to the spinal cord. When an injury interrupts the connection between the spinal cord and brain, it prevents signals from reaching below the site of the injury, EES can help to bridge the gap by providing electrical signals to the spinal cord below the injury site.
In rodents, cats, and even monkeys, EES has allowed “standing, walking in various directions, and even running,” write Courtine and his colleagues. They suggest that this technique has been less successful in humans because the electrical stimulation has been continuous, preventing feedback from the body to the brain, and effectively blocking the brain’s sense of where the limbs are in space. Physiological differences between humans and rats—including just the difference in body size—could explain why this affects humans and not rats, they suggest.
The systems needed to get more precise. And so the researchers set about understanding how the nervous system responded to movements in every joint in healthy individuals, building up a “map” of what these activation patterns looked like. Then they worked out where exactly the electrodes were needed to provide stimulation to match these activation patterns and built a system that would deliver shifting signals only to where they needed to be.
The researchers had to adjust the details for each of the three patients in the study, adapt