'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
"There must be some information getting from the brain past the spinal cord injury to the lower spinal cord that controls the movement of the legs, but the amount of information that's getting across is so small it's not enabling the patient to move," explained study co-author Reggie Edgerton, a distinguished professor of integrative biology and physiology at the University of California, Los Angeles. "The stimulation increases the excitability of the spinal circuits, enabling the person to perform some of these movements."
At this point, the electrical stimulator must be on for the men to be able to move. "One of the individuals can move sometimes without the electricity, but it's not as fine and not as strong," said senior study author Susan Harkema, director of rehabilitation research at the Kentucky Spinal Cord Injury Research Center at the University of Louisville.
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.