Paraplegic patient training with a robotic exoskeleton (Image: Alberto Santos Dumont Association for... [+] Research Support) A new rehabilitation approach has enabled eight paraplegic patients to regain feeling and movement in their legs. The high-tech training program uses virtual reality and feedback from robotic exoskeletons to rewire brain circuits. It has already allowed people to overcome complete paralysis of the lower limbs and could one day help others move around independently. This breakthrough comes from the Walk Again project, which originally aimed to find better ways for paraplegics to control prosthetics. Surprisingly, the training method also seems to reactivate the nerves controlling the lower limbs. "We thought this would be extremely useful to investigate the brain, and to eventually produce some kind of new assistive technology to restore mobility to patients using artificial prosthetic devices," says Professor Miguel Nicolelis, the Duke University neuroscientist who leads the project. "We never imagined that this could trigger any kind of clinical or neurological recovery." After studying how animals such as monkeys can be trained to control artificial limbs with their mind, Nicolelis organised an international collaboration between different specialists -- everyone from roboticists to rehab experts -- to create 'brain-machine interfaces' for medical applications in humans. The research led to a demonstration at the 2014 World Cup in Brazil, where a paraplegic man in an exoskeleton walked onto a football field to kick-off the opening ceremony. "This was the largest neuroscience project ever funded by the Brazilian government," says Nicolelis. VIDEO The Walk Again project began with eight people who had suffered traumatic injury to the spinal chord from severe accidents such as a car crash or fall. For between 3 and 13 years, patients had lived with complete paralysis of the lower limbs, no sensitivity to touch or pain below the level of injury, along with problems in the function of the bladder, gut and cardiovascular system. Brain-machine interface In the new study, eight patients trained for one hour a week through a brain-machine interface, which involved wearing a swimming cap with electrodes that record brain activity via EEG readings. Nerve signals to muscles were detected by the electrodes then translated into digital commands that controlled virtual limbs -- viewed on an Oculus Rift VR display -- or a real exoskeleton. But more importantly, the training provided tactile feedback: Nicolelis' team also built a "haptic display" with small motors that delivered vibration to a part of the body where paraplegics can still detect touch -- their arms. This haptic feedback was stimulated, for instance, by sensors on the exoskeleton's feet when pressure was applied to the ground. The training program therefore offered both visual and tactile feedback to a patient, allowing them to see and feel when their nerve signals had successfully moved an artificial limb. Patients claimed they could sense their legs moving or being touched -- even though the actual sensations were on their arms. Patient training with virtual reality and haptic feedback (Image: Alberto Santos Dumont Association... [+] for Research Support) Nicolelis believes the combination of visual and tactile feedback prompted the brain to create phantom limbs. "So that illusion I think was a key component to trigger the kind of functional recovery that we observed." The Walk Again project began training the paraplegic patients in December 2013. "Twelve months later, we were able to document the reemergence of voluntary motor control of muscles below the level of the injury," says Nicolelis. His training program was so successful that 50% of patients were reclassified from complete to partial paraplegia. One participant left the study (moving away from a clinic) but since June 2016, all seven remaining patients are now considered partial paraplegics. Rewiring neural circuits Why did the Walk Again project succeed where traditional rehab approaches, such as physiotherapy, nearly always fail? When measuring brain activity before patients had started training, Nicolelis' team could hardly detect any movement commands. "The concept of walking had been almost obliterated from their brains," he says. This suggests that it's not that paraplegics can't use their legs, but that they've forgotten how. Nicolelis believes his patients were able to regain movement because the lines of communication between body and brain hadn't been cut completely: a few nerve fibers in the spine had survived the accident that caused paralysis, then became inactive, and those circuits could be reopened by rewiring. The brain's flexibility in reorganizing connections -- known as "plasticity" -- is possible thanks to its ability to accept inputs from multiple sources. In the case of Walk Again training, the brain sent motor commands down the spinal chord while receiving signals from the movement of robotic limbs at the same time, which reinforced the circuits that moved a person's real legs. The Walk Again training program (Image CC BY 4.0: Donati et al / Scientific Reports) Although the paraplegic patients can't walk by themselves, they've made a remarkable recovery -- and they continue to improve. In another forthcoming study, Nicolelis will report that since December 2014, sensitivity in paralyzed areas of the body has doubled, and that sensory recovery keeps improving too. The Walk Again project has also recruited a second group of eight patients to try and reproduce results and determine the relative contribution of the various techniques -- virtual reality, robotic limbs and haptic feedback -- to the new training program. Nicolelis thinks the collaboration between researchers around the world will help paraplegic patients faster. "If we really invested our collected knowledge and resources, we could accelerate the process of providing for millions of people who suffer from spinal chord injuries with better therapies."
A virtual reality and feedback training program developed by the Walk Again Project has successfully helped all seven of its participants to become partial paraplegic, rather than full paraplegic. The program, which is being conducted in collaboration with the University of California, San Diego, aims to help people who have lost their legs or arms through amputation, paralysis, brain damage or other injuries.