Every year, close to 50,000 people suffer accidents and neurological disorders that lead to paralysis. Life dreams shatter in seconds, and to this day, the prospect for even partial recovery remains bleak.
But there are signs of hope on the horizon. Recent experiments at EPFL in Lausanne have shown how, through a better understanding of how to stimulate and interact with the body’s nervous system, we may one day be able to help victims of paralysis and other neurological disorders recover some of their mobility and with that, their autonomy.
To understand paralysis and how we hope to work around it, it is important to understand how the brain communicates with the rest of the body. Remarkably, it uses the same signals as modern computers: electricity. The brain, the body’s command centre, sends out electrical pulses that travel through the body along its nervous system.
These pulses orchestrate many physiological processes, including the motion of the limbs.
If in the event of an accident the nervous system is interrupted, everything downstream of the site of injury experiences the equivalent of a blackout. When this interruption occurs in the spinal cord, the nervous system’s main highway, it can lead to the permanent loss of sensitivity and motor skills of a large part of the body – paralysis.
Working with rats, our lab has been seeking ways to replace the nerve impulses from the brain that are no longer able to control hind limb motion of a fully paralysed animal with electrical pulses generated using a computer.
Our reasoning was that, if we could replicate the signals the brain produces in a healthy animal, and feed them into the nervous system below the site of injury, we might be able to artificially control the animal’s limbs.
As far-fetched as this sounds, we tested it and found it to work – on paralysed rats. Just last month, we published results of our laboratory experiments that showed that we were able to modulate the movement of the hind limbs of a rat with a severed spinal cord.
Although no nerve impulses could reach the hind limbs from the brain, the artificial stimulation enabled it to climb a set of stairs in an upright position, using a supporting robotic harness.
By modulating the frequency of the nerve impulses, we were even able to manually fine tune the height of its steps. To be clear, this motion is involuntary, because signals from the rat’s brain are unable to reach its hind limbs.
So what does that mean for victims of paralysis? The ability to artificially recreate nerve impulses that are understood by the body could mean that one day, we may be able to build a bridge over the injured site in the spinal cord.
This would require detecting the signals sent from the brain to the limbs before they reach the site of injury, replicating them using a computer, and feeding them back into the nervous system on the other side.
That is still stuff of the future, and we still have a long way to go if we want to see it become a reality. But we are on a mission.
Our next important step will be to find out whether these findings we have made on rats are transferrable to humans.
For that, we have set up a partnership with the University Hospital of the Canton of Vaud, in Lausanne, Switzerland, where we will embark on a series of clinical trials on victims of spinal-cord injury in a project called NeuWalk, using a new gait platform – a supporting harness developed specifically for the trials.
Gregoire Courtine holds the International Paraplegic Foundation Chair in Spinal Cord Repair at the Ecole Polytechnique Federale de Lausanne, in Switzerland.
