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A small group of paraplegic patients was once again able to take action after the researchers implanted a device to electrically stimulate their spinal cord.
Two separate teams of scientists revealed for the first time that the technique, combined with physical training, had allowed three out of five people treated to walk again after losing any voluntary movement under the site of the injury.
"It's amazing to be here and to really see them take their first steps," said Dr. Claudia Angeli of the Kentucky Spinal Cord Injury Research Center at the University of Louisville and co-author of one of the studies. "It's an emotional moment for the individual [themselves] because they were told that they could never do it again. "
In a study published in the New England Journal of Medicine, Angeli and colleagues report that they implanted a network of 16 electrodes in the lower back of four patients, paralyzed after mountain bike accidents or road accidents several years ago. The device, developed several years ago for pain control, was placed under the lesion site, covering regions that send sensorimotor signals to the legs while a battery is implanted in the body. the abdominal wall. , to tweak wirelessly. The electrical activity produced by the leg muscles was monitored during the sessions.
The approach – called epidural stimulation – works on the principle that there are still small signals from the brain that pass through the site of the spinal cord injury – even though these are not enough to generate voluntary movements.
How an implanted device could help paraplegic patients walk again
"We know that the spinal cord has the ability to organize a very detailed motor activity," Angeli said. "But before the injury, he received commands from the brain and he also received information from the environment."
The wound, she says, upsets that. "The spinal cord is isolated, it still potentially receives information from the environment, but it loses the fat driver, who was the brain."
Angeli said that it is thought that when the implanted device is turned on, the resulting electrical stimulation increases the excitability of the spinal cord – in a sense, making it more alert.
"It's like he's more conscious, he can actually listen to that little murmur of the brain that's still there and that can generate the motor model," Angeli said, adding that the drive for linking movements with these signals is crucial.
The four people had lost all motor control under the lesion site, although two of them had some level of sensation.
After implanting the device and locomotor training, the last two were finally able to walk without assistance. Kelly Thomas was able to walk after 81 stimulation sessions for 15 weeks, although she had to use a walking frame, while Jeff Marquis was able to walk a little over 90 meters without a break after 278 sessions over 85 weeks. Thomas, a 23-year-old from Florida, said, "Participating in this study really changed my life because it gave me hope that I did not think it was possible after my car accident."
The other two people were able to stand up and sit down independently. Another suffered a spontaneous fracture of the hip after one week of training and did not start again until a year later.
A separate article published by researchers at the Mayo Clinic in Minnesota and UCLA, published in the journal Nature Medicine, also reports success with the same approach. The team reveals that after 43 weeks of training with the implant, 29-year-old Jered Chinnock, paralyzed after a snowmobile accident and left with no sensation or willful movement under the injury, was able to walk unaided on a treadmill. holding on rails – and across the floor, but with a moving frame and a little human assistance to maintain balance. He did not find any sensation in his legs, however.
"The mind or thought of the patient was able to drive the movement in the legs," said Dr. Kendall Lee of the Mayo Clinic, one of the study's leading investigators, but he insisted on the fact that the mechanism remains unknown. must provide a very specific type of stimulation parameters. Random stimulation does not work, "he added.
None of the individuals could perform such actions when the pacemaker was disabled.
Angeli said that programming the device to give the best results takes time, and that there is a balance to be found when one adjusts the intensity of stimulation. If it is too low, the cerebral signals will still not be "heard" while, if it is too high, it can trigger an involuntary movement of the legs.
But she said hope the approach could help with more than just leg movement. "A future direction that we are starting now is to see if we are targeting epidural stimulation for [the] the bladder itself, so we can actually improve bladder control. "
Professor Gregoire Courtine of the EPFL Research Institute in Switzerland, who was not involved in either of the two studies, said he welcomed the research. But he said that a major problem is that the current applied to the electrodes is continuous, which means that it can only be of low intensity – which may not sound the "murmur" of the brain strong enough by the legs. Courtine said that he was working to solve this problem by synchronizing electrical stimulation with the intended movements – his previous work on monkeys used brain implants to capture brain movement signals and send them to the legs, bypassing the site. of the injury and allowing greater signal amplification to produce more robust muscle activity.
Mike Milner, CEO of the Nicholls Spinal Injury Foundation, has also been cautious, saying the research looks promising, the charity is supporting another approach to treating spinal injury injury.
"We are not only looking for a natural or biological cure for paralysis – but permanent treatment," he said.
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