Two other men involved in the study were also able to regain control of their leg muscles after they were implanted with electrical stimulators that could help compensate for the damage to their spinal cords, according to new research published in the journal Nature
The spinal cord
carries messages from the brain to other parts of the body, allowing us to move our limbs, feel sensations like pressure or temperature, and control vital functions.
If it is damaged, the neural signals can have trouble getting through, leaving a person paralyzed or otherwise disabled. In this experiment, researchers at the Swiss Federal Institute of Technology
in Lausanne used electrical implants to bridge the gap in the spinal cord, helping to carry the messages from the brain across the damaged area into a non-damaged part of the spinal cord lower down.
The effects of the treatment lasted beyond when the electrical signals stopped, and "all of the participants retained some improvement in muscle movement even after the stimulation therapy," according to Nature
While the results were astonishing, the team was quick to caution that the treatment -- called epidural electrical stimulation -- is in the early stages and it is not clear for how many people this would work. Importantly, the current sample size was very small, and all involved in the study retained some level of motor function below their injuries, even if this was not enough to walk unaided.
One positive sign about the study is that the electrical stimulation was not simply moving the muscles by itself, in the way that sending current through a dead body will make it twitch, but that it relied on the subjects attempting to move their limbs.
"It really works as an amplifier," study lead Grégoire Courtine told Nature. "It's not that we're taking over control of the leg. The patients -- they have to do it."
He said that after two days, the new movement became almost natural to the subjects and within a week, they were able to walk with limited assistance. This included one person previously had no movement in his legs, and one whose left leg had been completely paralyzed, according to Nature.
"Not so long ago, the hope that someone paralyzed for years by a severe spinal-cord injury would ever be able to walk again was just that -- hope," the journal said in an editorial about the new research
. "But recent advances are bringing those hopes closer to reality."
In a study published in the New England Journal of Medicine in September, researchers at the Kentucky Spinal Cord Injury Research Center at the University of Louisville described how two of four patients with "motor complete spinal cord injury" -- meaning no voluntary movement below their injury -- were able to walk again after being implanted with a spinal cord stimulation device and then undergoing extensive physical therapy. They walk with the aid of walkers.
"This should change our thinking about people with paralysis," said Susan Harkema, one of the lead researchers of that study who is a professor in the Department of Neurological Surgery at the University of Louisville when that study was published
. "It's phenomenal. This new knowledge is giving us the tools to develop new strategies and tools for recovery in people with chronic spinal injuries."
Another study also published in September in the journal Nature Medicine unveiled similar results. A man paralyzed since 2013 regained his ability to stand and walk with assistance due to spinal cord stimulation and physical therapy, according to research done in collaboration with the Mayo Clinic and the University of California, Los Angeles.
"What this is teaching us is that those networks of neurons below a spinal cord injury still can function after paralysis," Dr. Kendall Lee, the co-principal investigator and director of Mayo Clinic's Neural Engineering Laboratories, said in a press release when the study was released.
These studies provide important additional evidence to the continued advances being made in the spinal cord injury field Monica Perez, a professor in the Department of Neurological Surgery with the Miami Project to Cure Paralysis at the University of Miami said previously
. She said it shows more proof that people with severe paralysis often have residual connections that "can be engaged in a functionally relevant manner -- and that's amazing."
Patients like David M'zee who took part in the new study. The 30-year-old Swiss man was told by doctors he would never walk again after a sporting accident. Now he's able to walk around half a mile with the implant turned on.
"To me it means a lot. I'm surprised at what we have been able to do. I think you've got to try the impossible to make the possible possible. It's a lot of fun -- it feels really good," he told the BBC