Paraplegics who learned to control an Iron Man-like exoskeleton with their thoughts appeared to regain some feeling and function in their legs as a result of the training regimen, according to a new study.
The study, published Thursday in the journal Scientific Reports, describes how a year of training enabled participants with spinal cord injuries to recover some sensation, voluntary muscle contraction, and control over bowel function — evidence of neurological recovery that the authors were not expecting.
Four of the eight participants had their paralysis reclassified to a less severe level, although they still do not have control over most of their leg muscles.
“It turned out that six months into the training of these patients … we started realizing that the patients were experiencing an improvement in their neurological function,” said Dr. Miguel Nicolelis, a Duke University neurobiologist and senior author of the paper.
The training relied on what is known as a “brain-machine interface,” which decodes the brain’s signals into outputs aimed at enabling movement.
The study, which took place in Brazil, is not going to immediately change the course of therapy for the thousands of people with paraplegia around the world. The eight participants together took part in more than 2,000 training sessions to achieve small and what might not be sustainable gains.
But the results suggest that by using their thoughts to control an external device, participants were also jumpstarting some long-dormant nerve networks and connections in the brain and spinal cord.
“All this machinery is reactivated and you start bombarding the spinal cord — what’s left of it — with information,” Nicolelis said.
Brain-machine interfaces have been used to allow people who are paralyzed to move robots, trigger hand movements via electrodes on the arm, and, in the case of Nicolelis’s study, control an exoskeleton. At the opening of the 2014 World Cup in Brazil, a paraplegic participant kicked a ball while wearing the exoskeleton — a movement caused by the participant’s own thoughts routed through electrodes on his head to a computer to the exoskeleton.
In those cases, the interface acted as an assistive technology, helping patients control external devices. But the new study indicates that the interfaces might also serve as a therapeutic technology, restoring some level of function that the body had lost, said Dr. Elliot Roth, the medical director of the patient recovery unit at the Rehabilitation Institute of Chicago. Roth, who also chairs the physical medicine and rehabilitation department at Northwestern University Feinberg School of Medicine, was not involved in the study.
The results of the study need to be reproduced and researchers need to think how the technology could be applied to patients broadly, Roth said. But he called the study “an exciting first step.”
The participants in the study were injured three to 13 years ago. The goal of the project is to develop and refine the thought-controlled exoskeletons.
The training started with participants practicing moving an on-screen avatar with their thoughts. Electrodes captured their brains’ signals and translated them through a computer so that when participants imagined walking, the avatars walked. The participants also trained with a harness-like system that helped them stand and walk on a treadmill, and eventually, worked their way up to controlling the exoskeletons.
But as the participants trained, they regained some sensation in their lower limbs (although they could not sense changes in temperature) and some ability to voluntarily control muscles below the site of their injuries. Some of the participants saw improved bowel function and advances in their independence at home, such as being able to move themselves from their wheelchairs to the toilet. (The improvements in bowel and bladder control could also have come as a result of the participants being upright and out of their wheelchairs more often during the training program, not solely as a result of the interface training itself.)
The advances made by the participants are likely possible because some of the nerves at the site of their injury survive, as other research has shown. And with the intensive training, the brain’s cortex restarted firing the signals it once did to command the muscles in the legs to contract, reigniting the nerves at the site of the injury. Those nerves then relayed the messages onward to nerves in the legs.
“Something may have survived the original trauma, even if it were years ago,” Nicolelis said.
The training described in the paper took place mostly in 2014, but Nicolelis said the participants who have kept up with some level of training have continued to show progress. The recovery seen in one participant who left the study waned after several months.
Nicolelis’s approach is one of several that scientists are pursuing to restore mobility in patients with spinal cord injuries. Scientists are trying to reroute the brain’s signals around the site of injury, while others are trying to electronically stimulate a spinal cord. Still others think injecting new cells into the injury site could restore the cord’s function.
For now, Nicolelis said the new research amounts to a demonstration of a technology that deserves further study. But he said he and his colleagues are wondering how they could make the technology accessible if the results hold up.
“We’re already thinking about ways of disseminating this protocol,” he said.