In an astonishing breakthrough, patients left paralysed by severe spinal cord injuries have recovered the ability to move their legs after training with an exoskeleton linked to their brain – with one even able to walk using two crutches.

Scientists developed the Walk Again Project, based in Sao Paulo, Brazil, thinking that they could enable paraplegics to move about using the exoskeleton controlled by their thoughts.

But they were surprised to discover that during the training, the eight patients all started to regain the sense of touch and movement below the injury to their spine.

It was previously thought that the nerves in seven of the patients’ spines had been completely severed.

But the researchers now believe that a few nerves survived and these were reactivated by the training, which may have rewired circuits in the brain.

Writing in the journal Scientific Reports, they said: “While patient one was initially not even able to stand using braces when placed in an orthostatic posture, after 10 months of training the same patient became capable of walking using a walker, braces and the assistance of one therapist.

“At this stage, this patient became capable of producing voluntary leg movements mimicking walking, while suspended overground.

“In another example, patient seven … was capable of walking with two crutches and lower limb orthoses ... while requiring no assistance by a therapist.”

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Dr Miguel Nicolelis, director of the Duke University Centre for Neuroengineering in the US, said previously seven patients were classified as having total paralysis, but had now been upgraded to “partial paralysis”.

And he added: “The recovery has not stopped yet.”

He said the researchers had “never even imagined” this kind of effect would be possible and said they were now “very excited” at seeing what they believe is a “key milestone” in helping paraplegics.

The training involved the patients using virtual reality to control a computer avatar with a “brain-machine interface”. So when they thought about walking forward, the avatar would move as if it was their body.

They then used the same system to control a robot and finally an exoskeleton that the patients could wear.

At the opening ceremony for the World Cup in Brazil two years ago, a young man who had been paralysed from the chest down symbolically kicked off the tournament using a brain-machine interface and exoskeleton.

But it soon became apparent that the training was having a physical effect on their bodies.

“To our big surprise, what we noticed was the long-term training with brain-machine interfaces in different set-ups – in a virtual reality set-up, in a stand-alone robot or an exoskeleton controlled by brain activity – triggered a partial neural recovery, manifested by both partial motor, tactile, sensory and visceral recovery of functions in all of these patients,” Dr Nicolelis said.

“We are thinking that even though clinically all these patients were diagnosed repeatedly over more than a decade as being complete paraplegics – they didn’t have any movement or sensitivity – perhaps from an anatomical point of view, the original lesion didn’t destroy all the fibres in the spinal cord. Some may have survived and went quiet for many years.

“Due to the training that we created using brain activity to control devices directly but also providing very rich tactile feedback to patients and making them walk bipedally with our exoskeleton…we may actually have triggered a plastic reorganisation in the cortex.

“By re-inserting a representation of the lower limbs and locomotion in the cortex, these patients may have been able to transmit some of this information from the cortex through the spinal cord, through these very few nerves that may have survived the original trauma.

“It’s almost like we turned them on again and because of that we got the spinal cord activated by the cortex again and at the same time receiving feedback from the periphery [the limbs] again because these patients were walking in their training.”

The patients also regained a degree of control of their bladder and bowel control and their cardiovascular function also improved, which in one case resulted in a reduction in hypertension.

The researchers are not sure how much improvement the technique can achieve as the patients are continuing to correct.

Dr Nicolelis said: “Currently, once people with spinal injuries receive a diagnosis of complete paralysis, rehabilitation consists mainly of adapting them to a wheelchair.

“We believe that our results with this long-term, sustained brain-machine interface training can be not only critical itself in triggering recovery in our patients, but it can also serve as an important motivator for spinal cord patients worldwide.

“This has been a tremendous journey, to start working on this phenomenal project over 15 years ago on ideas first demonstrated in animals, and that are now showing revolutionary theories of how the brain works.

“The Walk Again Project scientists are making real impact in helping impaired people walk again. Seeing faces of young adults walking for the first time in many years has been life-changing for all of us.”

Raquel Siganporia, vice chair of the Spinal Injuries Association, said they were "encouraged to hear of the developments that the Walk Again Project has achieved and what it can mean for the future of spinal cord people".

"It is very promising to see research which takes steps into returning function and sensation to spinal cord injured people," she added.

"What is of particular interest is the fact that this technique saw a small improvement of other health issues such as hypertension and bladder and bowel function – elements which are vital in helping spinal cord injured people to live independent and fulfilling lives."

However she added that people with spinal injuries should "receive the news cautiously".

"The research is still at an early stage and currently only tested on a small minority of spinal cord injured people, namely paraplegics," Ms Siganporia said.