These four men have received an epidural stimulator implanted over the spinal cord that lets them move limbs they were told would never move again.

All four patients have gained back movement of their toes, knees, whole legs, ankles and trunk to varying degrees.

The device mimics the signals that the brain sends to the spinal cord.

Up next is a streamlined device that lets patients control their limbs with voice commands.

2014-04-08

How A New Technology Is Helping Paralyzed Patients Regain Use Of Their Legs

Four young men are now using an implant that lets them move limbs they were told would never work again. What does this mean for the future of paralysis?

Before Rob Summers had a spinal cord injury, he was a pitcher for the Oregon State Beavers with a win in the College World Series under his belt. He dreamed of being a major league baseball player. Then, on July 12, 2006, a car veered into his driveway and hit him as he stood outside his house. At 20, he was paralyzed from the neck down. Though he had some feeling below the waist, doctors said he would never walk again.

A decade ago, that may have been the end of the story. But Summers, along with three other young men with spinal cord injuries, have been given a new treatment--an epidural stimulator implanted over the spinal cord--that could change the way we think about paralysis. All of these patients, once completely paralyzed from at least the chest down, can now move their legs. The treatment, described in a study published today in the research journal Brain, is the result of research from scientists at the University of Louisville, UCLA, and the Pavlov Institute of Physiology, with funding from the Christopher & Dana Reeve Foundation and the National Institutes of Health.

Summers was the first to get the implant, and a study discussing his recovered motor functions post-implant was published in 2011. Now researchers know that his results can be repeated--including on two patients diagnosed as "motor and sensory complete," meaning they were never expected to gain back any function at all. All four patients have gained back movement of their toes, knees, whole legs, ankles, and trunk to varying degrees when the stimulator--which mimics signals that the brain usually sends to the spinal cord to initiate movement--is turned on. And over time, with training, they've been able to gain back more movement with less stimulation, showing that the spinal cord can improve nerve function.

"The concept is that the brain sends a simple straightforward signal, the spinal cord responds, and it has complex signals that execute the details of the movement," explains Dr. Susan Harkema, a professor at University of Louisville and the director University of Louisville’s Kentucky Spinal Cord Injury Research Center (KSCIRC). "That's why when we turn the stimulator on, there's a tiny residual signal that comes from the brain, which must be pretty minimal. It certainly must be very, very small and it can't be complex because there's not much remaining. If you can optimize the spinal cord, it can respond even to that faint signal."

For over 15 years, Harkema has worked to understand the role of the human spinal cord in generating locomotion. Researchers have known for a long time that movements like swimming, walking, galloping, and running are controlled by neurons in the spinal cord, not the brain--at least in other animals. But humans were thought to be different. "When I started my career, I was asking whether the human spinal cord had any of those properties," she says.

Harkema studied people with complete spinal cord injuries for over a decade, gathering evidence for her hypothesis that it was possible to change the output of the nervous system with the kind of repetitive training associated with walking. This led to a therapy called locomotor training--where patients stand and step with body weight support and a treadmill--that's just beginning to take hold. Locomotor training only works, however, for people with incomplete spinal cord injuries. Anyone with a complete spinal cord injury (someone who lacks all motor control and feeling below their injury) won't benefit. But even patients with complete spinal cord injuries can benefit from epidural stimulator implants, according to the new study.

Initially, Summers hoped to do rehab with the Reeve Foundation's NeuroRecovery Network, but he couldn't get in. "For me, the spinal cord injury affected my core strength. Even after going back to TIRR [The Institute for Rehabilitation & Research in Houston] a second time, I still didn't qualify. It was at that point I opted to go to the research side," he says.

In December of 2009, he received an epidural stimulator implant. "Going into it, I spent months reading every article dating back to the 1950s that had ever been written on epidural stimulation, animal models, and hypotheses--the science behind it, the theories that went along with it," he says. "After the surgery was over, it was kind of like, 'That was step one and now the hard work begins.' It takes me back to my athletic mindset days."

On the third day of post-implant therapy, he was put in a harness over a treadmill, and stood independently for the first time in four years. "In the moment, it was gameface on. I didn't really think about what was going on except the mission at hand, and as soon as we were able to reflect on what happened, it was tears in joy," he says.

About six months into his therapy, Summers was sitting on a table hooked up to electrodes, surrounded by doctors and scientists. He was talking to his head trainer therapist, and started laughing. "You should take a look at this," he told her. "I can move my toes on command."

"Her jaw about hit the floor at that point," Summer says. After that incident, Summers began voluntary movement training. Now he can move his toes, ankles, knees and hips, He can do sit-ups, he has increased muscle tone, and better blood flow and circulation. Thanks to his discovery, the three research participants following Summers regained voluntary movement almost immediately after receiving the stimulator implant.

All four of the participants have varying levels of movement in their legs. "They all can move every joint, but how many times or how much strength does vary across them. We don't know if it's because of differences in injuries or the time they were implanted. Also, as we implanted and trained, we learned from the person [who had received the implant before]," says Harkema. It will take us time to sort those things out, to understand how far this can actually go and who's more likely to respond. What was surprising to us is that four out of the first four all have responded."

The participants have also seen positive changes in the secondary consequences of their spinal cord injuries--problems like poor heart function, poor circulation, atrophy, and bone density are all getting better.

Now Harkema and the rest of the research team need to improve the epidural implant technology. The stimulator used on the first four participants is an off-the-shelf stimulator used for pain management. The interface is too slow, and it requires each patient's control algorithm to be changed periodically by a human being.

Harkema would ideally like a voice-activated interface (or one that can be activated with a single button). Also, she says, "the stimulator itself needs to be more flexible. Right now, if you want to change configuration, you have to turn it off and start it up again. There's a hardware redesign and a software redesign that needs to happen," she says. Looking further into the future, she imagines a smartphone-like device that would let a patient could say "I'd like to move my leg," and the stimulator's configuration automatically changes.

She also stresses the importance of the changes in the aforementioned secondary consequences, which will most easily translate into a clinical setting.

"One of the big take-home messages is that our preconceived notions that people with severe paralysis have no hope of recovery needs to be scrutinized and looked at and challenged," says Harkema. "We purposely took individuals that by all clinical and scientific measures would be considered having no hope of being able to move or stand or change their neurological health status, especially after so many years of injury. This tells us that it's the most severely injured who need the most intense rehab."

Summers, now a motivational speaker and youth baseball coach, says that his six-day-a-week therapy has made life much easier. "I'm in and out of a car in 30 seconds. The first time I tried [after being injured], it was 20 minutes in, 15 minutes out," he explains. "I have the freedom to go to any restaurant, go out in public, travel as much as I travel, do the things I do, and not have to worry about it."

He's hopeful that eventually, with updated stimulator technology, he'll one day be able to walk.

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