Implant Enables Man With Severed Spinal Cord to Walk
In a world first, Michel Roccati, a man with a completely severed spinal cord was able to walk again outside the lab with the help of a portable electrical stimulation system that causes his legs to take a step in conjunction with his intention to move and a walker to steady him.
This was a further development of a technology that in 2018 helped David M’zee, who had been left paralysed by a partial spinal cord injury suffered in a sports accident, to walk again. A research team led by Professors Grégoire Courtine, at École Polytechnique Fédérale de Lausanne (EPFL) and Jocelyne Bloch, at Lausanne University Hospital (CHUV) had developed an electrical stimulation system to help people with spinal cord injuries walk again.
They had wanted to see if electrodes could stimulate movement in the parts of the spine damaged so badly that signals no longer reach the nervous system from the brain. That pioneering study was detailed in Nature and Nature Neuroscience. Thanks to the electrodes making up for the weakness of the signals in his damaged spinal cord, M’zee was able to voluntarily move his legs and could walk several hundred metres at a time, sometimes without the aid of the rails on the treadmill.
Now a new milestone has just been reached with the technology, and the research team enhanced their system with more sophisticated implants controlled by advanced software. These implants can stimulate the region of the spinal cord that activates the trunk and leg muscles. Thanks to this new technology, three patients with complete spinal cord injury were able to walk again outside the lab. “Our stimulation algorithms are still based on imitating nature,” said Prof Courtine. “And our new, soft implanted leads are designed to be placed underneath the vertebrae, directly on the spinal cord. They can modulate the neurons regulating specific muscle groups. By controlling these implants, we can activate the spinal cord like the brain would do naturally to have the patient stand, walk, swim or ride a bike, for example.”
On a cold, snowy day last December, Michel Roccati – an Italian man who became paralysed after a motorcycle accident four years earlier – braved the icy wind to try out the system outdoors, in central Lausanne. He had recently undergone the surgical procedure in which Prof Bloch placed the new, implanted lead on his spinal cord.
Scientists attached two small remote controls to Michel’s walker and connected them wirelessly to a tablet that forwards the signals to a pacemaker in Michel’s abdomen. The pacemaker in turn relays the signals to the implanted spinal lead that stimulates specific neurons, causing Michel to move. Grasping the walker, Michel pressed a button corresponding to either the left or right leg with the firm intention of taking a step forward, and his feet rose and fell in short steps.
“The first few steps were incredible – a dream come true!” he says. “I’ve been through some pretty intense training in the past few months, and I’ve set myself a series of goals. For instance, I can now go up and down stairs, and I hope to be able to walk one kilometre by this spring.”
Two other patients have also successfully tested the new system, which is described in Nature Medicine. “Our breakthrough here is the longer, wider implanted leads with electrodes arranged in a way that corresponds exactly to the spinal nerve roots,” said Bloch. “That gives us precise control over the neurons regulating specific muscles.” Ultimately, it allows for greater selectivity and accuracy in controlling the motor sequences for a given activity.
While extensive training is necessary for patients to get comfortable using the device, the speed and scope of rehabilitation is amazing. “All three patients were able to stand, walk, pedal, swim and control their torso movements in just one day, after their implants were activated!” said Prof Courtine. “That’s thanks to the specific stimulation programs we wrote for each type of activity. Patients can select the desired activity on the tablet, and the corresponding protocols are relayed to the pacemaker in the abdomen.”
While the progress achievable in a single day is astonishing, the gains after several months are even more impressive. The three patients followed a training regimen based on the stimulation programs and were able to regain muscle mass, move around more independently, and take part in social activities like having a drink standing at a bar. What’s more, because the technology is miniaturized, the patients can perform their training exercises outdoors and not only inside a lab.
Presently there is one key limitation, Prof Bloch said: “We need at least six centimetres of healthy spinal cord under the lesion. That’s where we implant our electrodes.”
As for Roccati, after nine months of Lausanne-based rehab, he now lives independently in Italy. “I continued rehab at home, working alone, with all the devices,” he said. “And I see improvements every day.”
