There have always been three lines of hope for someone with spinal cord injury and partial paralysis.
The first is to ask can the injury be repaired? Is there some process or management that can encourage nerve tissue to heal? Better management of the condition, from the scene of the accident to physiotherapy in the hospital bed, can and does now help many who might once have condemned to immobility.
The second is: if the break is complete, is there some way to stimulate renewal and repair? Many simpler forms of life manage it, why not mammals? This was best known for a while as the dream of Christopher Reeve. The actor, who in 1978 played Superman, damaged his spine in a horse-riding accident in 1995 and died in his wheelchair in 2004. He campaigned for embryo stem cell therapy, a technology that could encourage nervous tissue to grow again, and launched the Christopher Reeve Foundation to finance such research.There have been encouraging results, but mostly, so far, in laboratory rats.
Finally, the third line of hope is: can technology bypass the spinal fracture and make a silicon link between brain and muscles? This is roughly what the Walk Again Project scientists in Brazil were aiming for when they delivered what looked very much like the first flickering and still very tentative realisation of the Christopher Reeve dream.
But instead, they may have discovered a way to advance the first approach. Paul Matthews, head of brain sciences at Imperial College London, thinks it significant that seven of the eight patients were diagnosed with severe “closed” injury. That is, their spines were crushed rather than severed. If so, there very well may have been nervous connections that survived.
And if so, then what happened to the patients was what has often happened to injury victims: in such cases the signals through the nervous system are blocked, and first the muscles weaken and atrophy through misuse. And then the brain seems to “forget” how to make the connection anyway. So if nerves did have the capacity to regenerate, the repaired nerve might not be able to find the chemical and electrical signals that turn a wish into a deed: a simple movement of a leg, for instance.
“What scientists learned over the past few years is that a degree of learning and plasticity of the nervous system is possible, even in the context of relatively severe injuries. The gains have been typically modest but nonetheless they do appear to be real and the ability seems to be sustained for long periods after injury,” said Professor Matthews.
In the case of the Brazil patients, some nerves might have been seriously injured, while others survived but atrophied with misuse. “What this exoskeleton is probably doing are two things. One is it is setting up a pattern. It is forcing the limb to take on ecologically reasonable movement, driven by the individual,” he said.
“The second is that as a consequence of that, those surviving parts upstream of damaged nerves are being repetitively stimulated in ways that may help to promote some degree of regrowth,” he said.
“The things that is really special about this approach – and it means it is not just a trivial extension of what went before - is they are using signals from the individual’s own brain. When we do things with our brain we are sending signals down at the same time we are expecting some response to come up. It is that that makes it very different.”