Image: Kent Stephenson, the second person to undergo epidural stimulation of the spinal cord, voluntarily raises his leg (Photo courtesy of KSCIRC).
Epidural electrical stimulation of the spinal cord has allowed four young men who have been paralyzed for years to move their legs voluntarily.
Researchers at the University of Louisville (UL; KY, USA), The University of California, Los Angeles (UCLA, USA), and the Pavlov Institute of Physiology (Saint Petersburg, Russia) implanted an epidural stimulator delivering a continuous electrical current to lower spinal cords of the participants, who were classified as suffering from chronic, motor complete spinal cord injuries, and were unable to move their lower extremities. Once the signal was triggered, the spinal cord reengaged its neural network, allowing the participants to control and direct muscle movements.
In epidural stimulation, an electrical current is applied at varying frequencies and intensities to specific locations on the lumbosacral spinal cord, corresponding to the dense neural bundles that largely control the movement of the hips, knees, ankles and toes. Coupling epidural stimulation with rehabilitative therapy intensified therapy impact, and participants were able to initiate movement with less stimulation, demonstrating the ability of the spinal network to learn and improve nerve functions. Beyond regaining voluntary movement, the participants enjoyed overall health improvement, including increased muscle mass, blood pressure regulation, reduced fatigue, and dramatic improvements in their sense of well-being.
The study builds on initial research—published in May 2011 in the Lancet
—that evaluated the effects of epidural stimulation in the first participant, Rob Summers of Portland (OR, USA), who recovered a number of motor functions as a result of that intervention. Three years later, the new study reports the impact of epidural stimulation on Summers and another three participants, who were all able to execute voluntary movements immediately following implantation and activation of the stimulator. The participants' results and recovery time were unexpected, which led researchers to speculate that some pathways may be intact post-injury and therefore able to facilitate voluntary movements. The study was published in the April 4, 2014, issue of Brain.
“Two of the four subjects were diagnosed as motor and sensory complete injured with no chance of recovery at all,” said lead author Claudia Angeli, PhD, an assistant professor at the UL Kentucky Spinal Cord Injury Research Center (KSCIRC). “Because of epidural stimulation, they can now voluntarily move their hips, ankles, and toes. This is groundbreaking for the entire field and offers a new outlook that the spinal cord, even after a severe injury, has great potential for functional recovery.”
"This is a wake-up call for how we see motor complete spinal cord injury,” said coauthor V. Reggie Edgerton, PhD, distinguished professor of integrative biology and physiology, neurobiology, and neurosurgery at UCLA. “We don't have to necessarily rely on regrowth of nerves in order to regain function. The fact that we've observed this in four out of four people suggests that this is actually a common phenomenon in those diagnosed with complete paralysis.”
“This research brings up an amazing number of possibilities for how we can develop interventions that will help people recover movement they have lost,” added Dr. Edgerton, who is also a member of the Reeve Foundation (Short Hills, NJ, USA) International Research Consortium on Spinal Cord Injury, which helped fund the research. “The circuitry in the spinal cord is remarkably resilient. Once you get them up and active, many physiological systems that are intricately connected and that were dormant come back into play.”
University of Louisville
The Pavlov Institute of Physiology