Los Angeles, California:
A new noninvasive method of stimulating the spinal cord has for the first time allowed five completely paralysed men to move their legs in a walking motion, scientists say.
The strategy, called transcutaneous stimulation, delivers electrical current to the spinal cord by way of electrodes strategically placed on the skin of the lower back.
This expands to nine the number of completely paralysed individuals who have achieved voluntary movement while receiving spinal stimulation, though this is the first time the stimulation was delivered non-invasively.
Previously it was delivered via an electrical stimulation device surgically implanted on the spinal cord.
In the study, the men's movements occurred while their legs were suspended in braces that hung from the ceiling, allowing them to move freely without resistance from gravity.
Movement in this environment is not comparable to walking; nevertheless, the results signal significant progress towards the eventual goal of developing a therapy for a wide range of individuals with spinal cord injury.
The study was conducted by a team of researchers at the University of California, Los Angeles; University of California, San Francisco; and the Pavlov Institute, St Petersburg, Russia.
The five men - each paralysed for more than two years - underwent a series of 45 minute sessions, once a week, for approximately 18 weeks, to determine the effects of non-invasive electrical stimulation on their ability to move their legs.
In addition to stimulation, the men received several minutes of conditioning each session, during which their legs were moved manually for them in a step-like pattern.
For the final four weeks of the study, the men were given the pharmacological drug buspirone, which mimics the action of serotonin and has been shown to induce locomotion in mice with spinal cord injuries.
At the initiation of the study, the men's legs only moved when the stimulation was strong enough to generate involuntary step-like movements.
However, when the men attempted to move their legs further while receiving stimulation, their range of movement significantly increased, researchers said.
After just four weeks of receiving stimulation and physical training, the men were able to double their range of motion when voluntarily moving their legs while receiving stimulation.
The researchers suggest that this change was due to the ability of electrical stimulation to reawaken dormant connections that may exist between the brain and the spinal cord of patients with complete motor paralysis.
By the end of the study, and following the addition of buspirone, the men were able to move their legs with no stimulation at all and their range of movement was the same as when they were moving while receiving stimulation.
The study was published in the Journal of Neurotrauma.