Three men with paralyzing spinal cord injuries can now stand, walk and cycle after electrodes were implanted into their spinal cords.
The electrodes deliver electrical pulses to specific regions of the spinal cord and thus activate muscles in the trunk and legs, according to a new study, published Monday (Feb. 7) in the journal Nature Medicine (opens in new tab). The soft, flexible device lies directly on top of the spinal nerves, beneath the vertebrae, and can be controlled wirelessly with software, operated from a tablet, and a handheld clicker.
The software communicates with a pacemaker-like device in the abdomen, which then directs the activity of the nerve-bound electrodes on the spinal cord. So, with the tap of a touch screen, the user of the implant can prompt their device to generate a precise pattern of stimulation. These stimulation patterns translate to patterns of muscle activity, allowing the user to walk, cycle, or swim, for instance. Users can also manually switch between these stimulation patterns with their clicker.
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"All three patients were able to stand, walk, pedal, swim and control their torso movements in just one day, after their implants were activated," co-senior author Grégoire Courtine, a neuroscientist and professor at the Swiss Federal Institute of Technology Lausanne (EPFL), said in a statement (opens in new tab). The three patients were men, ages 29 to 41, but the study authors also expect that the device will work in women, The Guardian reported (opens in new tab).
After the initial implantation, the patients underwent extensive training to get used to using the device and regain muscle mass and motor control, co-senior author Dr. Jocelyne Bloch, an associate professor of neurosurgery at Lausanne University Hospital, told The Guardian. "It was not perfect at the beginning, but they could train very early to have a more fluid gait," she said. Eventually, the patients progressed from using the implants only in a controlled lab setting to using them out and about in their daily lives.
After four months of training, one patient, Michel Roccati, was able to walk about 0.6 mile (1 kilometer) outside the lab and without stopping, with only a frame for balance, AFP reported (opens in new tab). He can now continuously stand for about two hours. Like the other participants in the trial, Roccati has a complete spinal cord injury, meaning the nerves below his site of injury cannot communicate with the brain at all. He was injured in a motorcycle accident in 2019 and lost both feeling and motor control in his legs.
"It was a very emotional experience," Roccati said of the first time the electrical pulses were activated and he took a step, AFP reported. Now, the device is "a part of my daily life," he told The Guardian. At a news conference, Roccati said he's regained some feeling in his legs; he can feel his body making contact with the ground and his muscles engaging when he walks, STAT reported (opens in new tab).
The new device builds on existing technology called spinal cord stimulators, which are already used to alleviate pain, according to NBC News (opens in new tab). The team modified these stimulators to target specific nerves involved in controlling muscles of the legs and lower trunk, they wrote in their report. In addition, in the trial, the team custom-fit each implant to match the length of the spinal cord and the position of the nerves in different participants, according to STAT.
"That gives us precise control over the neurons regulating specific muscles," Bloch said in the statement. "Ultimately, it allows for greater selectivity and accuracy in controlling the motor sequences for a given activity."
The device will now be tested in a large-scale trial in the U.S. and Europe, according to STAT. The team hopes to test the device in people with relatively recent injuries; in the three-person trial, all of the participants were at least a year out from their injuries. "The next step is to start earlier, just after the injury, when the potential for recovery is much larger," Bloch told NBC News. Animal studies hint that electrical stimulation may help the spinal cord heal after injury, according to STAT; so patients could potentially regain more sensation and motor control if their implant is placed soon after injury.
The team is also investigating whether a similar stimulator could be implanted directly into the motor cortex, a key region of the brain for controlling voluntary movement, Courtine told NBC News. Such a device could allow people with paralysis to direct their movements without the aid of a tablet or clicker.
The treatment's accessibility has limitations, however: Placement of the implant requires invasive surgery, and patients must undergo extensive monitoring and rehabilitation after the implantation, ABC Science reported (opens in new tab).
"The challenge for the future is not only improving these approaches and developing other approaches, but to manage the application of these interventions so that many individuals can benefit, given that the access to high levels of technology may be an impediment," Reggie Edgerton, a professor at the University of California, Los Angeles who oversaw some of Courtine's postdoctoral work, told STAT.
Originally published on Live Science.