A man has been able to move all four of his paralysed limbs using a groundbreaking mind-controlled exoskeleton, scientists have said.
The tetraplegic 30-year-old, known only as Thibault, said his first steps in the robotic suit felt like being "the first man on the Moon".
The system, which works by recording and decoding brain signals, was trialled in a two-year study by French researchers at biomedical research centre Clinatec and the University of Grenoble.
Scientists conceded the suit was an experimental treatment far from clinical application but said it had the potential to improve patients' quality of life and autonomy.
Wearing the robotic limbs, Thibault was able to walk and move his arms using a ceiling-mounted harness for balance.
The Frenchman had worked as an optician before he was paralysed from the shoulders down after falling 15m at a nightclub in 2015.
As part of the trial, he had surgery to place two implants over the parts of the brain that control movement. Sixty-four electrodes on each implant read his brain activity and beamed the instructions to a computer.
Software then read the brainwaves and turned them into instructions to control the exoskeleton.
"It was like [being the] first man on the Moon," Thibault said. "I didn't walk for two years. I forgot what it is to stand, I forgot I was taller than a lot of people in the room."
A second patient recruited to the study was excluded because a technical problem prevented the brain implants from communicating with the algorithm.
Professor Alim Louis Benabid, a leading neurosurgeon at the University of Grenoble, said the exoskeleton used was the first semi-invasive wireless brain-computer system designed for long-term use to activate all four limbs.
"Previous brain-computer studies have used more invasive recording devices implanted beneath the outermost membrane of the brain, where they eventually stop working," he said. "They have also been connected to wires, limited to creating movement in just one limb or have focused on restoring movement to patients' own muscles."
The study, published in The Lancet's Neurology journal, involved Thibault performing mental tasks, including computer games, to train an algorithm to understand his thoughts and progressively increase the number of movements he could make.
His progress was measured in the degrees of freedom he had during tasks, such as operating a brain-powered switch to start walking or reaching out to touch objects.
Prof Benabid said Thibault "already considers his rapidly increasing prosthetic mobility to be rewarding", although the exoskeleton suit "has not changed his clinical status".
Professor Tom Shakespeare, of the London School of Hygiene and Tropical Medicine, cautioned the technology was a long way from being a realistic clinical possibility and may never be feasible for many patients.
"A danger of hype always exists in this field," he said. "Even if ever workable, cost constraints mean that hi-tech options are never going to be available to most people in the world with spinal cord injury."
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