In a breakthrough, four paralysed young men have been able to voluntarily move their legs for the first time in years after electrical stimulation of their spinal cords.
The men were classified as suffering from chronic, motor complete spinal cord injuries and were unable to move their lower extremities prior to the implantation of an epidural stimulator.
The stimulator delivers a continuous electrical current to the participants' lower spinal cords, mimicking signals the brain normally transmits to initiate movement.
The new research builds on an initial study, published in 2011 in the journal The Lancet. It evaluated the effects of epidural stimulation in the first participant, Rob Summers of Portland, who recovered a number of motor functions as a result of the intervention.
Now, three years later, the findings of the new study documented in the journal Brain, detail the impact of epidural stimulation in a total four participants, including new tests conducted on Summers.
Summers was paralysed after being struck by a vehicle, and the other three participants were paralysed in auto or motorcycle accidents.
What is revolutionary, the scientists said, is that the second, third and fourth participants were able to execute voluntary movements immediately following the 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.
"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, an assistant professor at University of Louisville's 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," Angeli said.
In epidural stimulation, the 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.
With the participants, once the signal was triggered, the spinal cord reengaged its neural network to control and direct muscle movements.
When coupling the intervention with rehabilitative therapy, the impact of epidural stimulation intensified.
Over the course of the study, the researchers noted that the participants were able to activate movements with less stimulation, demonstrating the ability of the spinal network to learn and improve nerve functions.
