Quirks & Quarks

Spinal injury patients take steps again thanks to spinal pacemaker

The scientists programmed the device to stimulate the muscles in a certain sequence for walking

The scientists programmed the device to stimulate the muscles in a certain sequence for walking

David Mzee is now able to step on his own - even without stimulation. (EPFL / Jamani Caillet)
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Three different paraplegic patients with spinal cord injuries have been able to take a few steps for the first time since their injuries thanks to a new device that was implanted onto their spinal cord.

By electrically stimulating the nerves connected to their leg muscles in a carefully programmed way, it was able to train their bodies to move again.

David Mzee was one of the three patients who participated in the trial with this stimulating technology. In 2010 he broke his neck and lost the use of his legs in a trampoline accident, and it seemed likely that he would never walk again. But after a long and difficult period of training with this technology, he was finally able to take steps on his own.

"It was just fantastic — I could really walk on my own," said Mzee. "Of course the stimulation was helping me, but it felt like I was doing the job. I could accelerate and I could make bigger steps and smaller steps as I wanted. And that was really an amazing feeling."

One of the scientific team members behind this study is Canadian Jordan Squair, a post-doctoral fellow at the Swiss Federal Institute of Technology.

"What we've actually done is we, for each patient, have programmed different patterns of stimulation such as standing up, walking slowly, walking quickly." said Squair. 

How the device works

The implant is a 16-electrode array that is surgically placed onto the spinal cord. The goal is to harness the potential residual control left behind in the spinal cord after an injury.

For about a month, the team would manually stimulate every single possible combination of these electrodes and recording the muscle activity to make sure they learn they're recruiting the right muscle in the right order.

"And so for each patient they spent about a month mapping every single one of these spots on this array and what muscles that would activate," said Squair.

I could accelerate and I could make bigger steps and smaller steps as I wanted. And that was really an amazing feeling.- David Mzee, paraplegic patient 

Once they had this map, they'd program it to stimulate the muscles in a certain sequence to train their body in a certain way.

These first few sessions, the individuals don't typically feel like they have a lot of control, but as they do this over and over and over throughout the rehabilitation protocol, they eventually learn how to control the stimulation," said Squair.

Retraining the muscles

By providing a small amount of electrical current via the device to the spinal cord, it reawakens the circuits that are still intact. Then over time, the individuals learn how to activate those circuits again on their own by reinforcing the residual connections between the brain and the spinal cord.

"We know from classical pathological studies in humans that even in very severe spinal cord injuries ... it's quite rare for there to be actually a complete transaction of the spinal cord," said Squair.

"When it started working nicely and I could control and influence the stimulation the way I wanted and I could let the hands go walk freely — that was amazing," said Mzee.

David Mzee taking a few steps with a walker at École polytechnique fédérale de Lausanne. (EPFL / Jamani Caillet)

After several months of training, test subjects like Mzee were finally able to voluntarily move the joints in his leg even in the absence of stimulation.

"I was actually present for the first time that Mzee came into the lab and surprised us and said, 'Can you set up the bar as for me? I'm going to just walk five steps,'" said Squair. "And he said, 'OK, I'm going to turn the stimulation on.' And then he walked five steps towards me and then he said, 'Actually guys, I didn't turn the stimulation on!' That was the first time that he had done that for us and it was it was really incredible and quite a cool moment to be a part of."

This experiment has remarkable potential, but Mzee is still, for the most part, confined to his wheelchair. He can take a few steps with a walker, but that's been the limit of his recovery.

"It was a long and hard journey," said Mzee. "But I think it was worth it."