'Milestone' Therapy: Leg Movement in Paraplegics
Electrodes along spinal cord gave four men ability to flex toes, ankles and knees, but it's no cure, researchers report
The research revolves around a spinal cord stimulation unit that sends a constant stream of energy into the spinal cord through an array of 16 electrodes implanted beneath the bone of the spine, Harkema explained.
Summers received the implants in December 2009. The goal, said researchers, was to increase the sensitivity of local circuits within the spinal cord that carry out basic motor functions without input from the brain.
The stimulator worked as planned, with Summers' feet and quadriceps moving on their own. "It feels like pins and needles, like if you fell asleep on your arm and then your arm started to wake back up," he said.
The immediate results startled researchers. "The first experiment, he actually moved his toes and his legs," Harkema said. "We really had to rethink how a human being controls movement."
Part of the sensory pathway in Summers' legs was still intact after he was paralyzed in July 2006 when a car hit him as he stood in his own driveway. "He still had some feeling there, so we knew there was still a connection to the brain," Harkema said. "There were still some signals there."
So they tried the implants on three more men, including two receiving no sensation from their legs. All moved the first time they turned on the electrical stimulator, Harkema said, and within days were able to control some movement.
The main point, Edgerton said, "is in four out of four subjects we've observed something that 99.9 percent of the scientists or anyone else would say could not have occurred. This tells us there is new potential within the spinal cord we have yet to take advantage of."
What's more, all of the men had been paralyzed for longer than two years. "We have shown the plasticity of the brain and the spinal cord is not limited to the first six to 12 months after the injury," Edgerton said. "It can persist for years."
The next steps are to improve the technology behind the electrical stimulator and to test more patients, Harkema said. The NIH and the Christopher & Dana Reeve Foundation partly funded the treatment for the first four patients, and researchers are looking for funding to provide implants for dozens more.
"I think if we could do 30 to 40 more, that would really open the evidence of how clinically relevant this is," she said.
In addition, the current results were gained using a device originally developed to help people control pain, Pettigrew said. Researchers want to develop a next-generation model specifically to create mobility in paraplegics -- perhaps even one with electrodes placed on the skin, so no surgery is required.
Summers believes this research will eventually allow him to walk.
"My ability to stand continues to get stronger and more independent," he said. "I absolutely believe 100 percent that mobility and functionality is right around the corner."