The Lancet Neurology
A paralysed man has been able to walk again using an exoskeleton suit he controls with his mind. Although it doesn’t yet let him walk independently – the suit is suspended from an overhead harness to stop him from falling – the advance represents the first steps down the road to this goal.
“This is really groundbreaking,” says Ravi Vaidyanathan of Imperial College London, who wasn’t involved in the work.
The implanted brain sensors also let the man, who broke his neck in a fall four years ago, move the arms and hands of the exoskeleton.
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Several groups are working on ways to let people with spinal cord injuries regain control over their bodies by reading their thoughts. So far, the most common approach has been to insert ultrathin electrodes into the brain.
But this entails having wires entering the skull, which could let in an infection. The electrodes also gradually stop working so well over the following months as they get covered with cells that form a kind of scar tissue.
To get round these problems, Alim Louis Benabid at the University of Grenoble Alpes in France and his colleagues instead put electrodes on top of the brain, resting on its tough outer membrane. “If there’s any kind of infection, it will stay outside,” says Benabid.
The researchers started by asking the man, a former optician known as Thibault, to have several brain scans so they could map which areas become active when he thinks about walking or moving his arms. Then they replaced two 5-centimetre discs of skull, one on either side of his head, with the brain sensors, which have electrodes on their underside.
Thibault practised using the sensors, first by trying to move an avatar shaped like the exoskeleton on a computer. Then he was strapped into the suit and he learned to make it start walking forwards, while supported from overhead.
“I felt like the first man on the moon,” says Thibault. “I hadn’t walked for two years. I had forgotten that I used to be taller than a lot of people in the room. It was very impressive.”
The team’s next goal is to make the exoskeleton self-balancing. “What we need is higher computation speed – we don’t yet have the reaction time,” says Benabid.
“Imagine all the adjustments you take to stay on your feet,” says Vaidyanathan. “If you could count on the robot for some stabilisation, then walking is potentially achievable.”
Thibault also learned to use the suit’s arms for increasingly complex tasks, such as rotating his wrists, reaching out to targets and using both hands simultaneously.
However, the work didn’t go smoothly. Before Thibault, there was another person who had the implants put in, but they stopped working within a few seconds of being turned on, due to a technical fault. “He was disappointed,” says Benabid.
Now that problem has been fixed and there have been good results with Thibault, the team is about to put implants into three more people.
The fact that Thibault’s implants are still working after 27 months is highly promising, says Vaidyanathan. “Obviously it has a long way to go before it can be generally used, but this is a pivotal step.”
Journal reference: The Lancet Neurology, DOI: 10.1016/S1474-4422(19)30321-7
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