A team of neuroscientists in Switzerland have helped a paralyzed man walk again 12 years after a severe motorcycle accident. Their secret? An experimental implant that helps facilitate central nervous system activity by bridging the gap between the brain and the spinal cord.
Walking might be a relatively simple activity for some, but it requires behind-the-scenes orchestration between the brain, spinal cord, and leg muscles. To tell the legs to move forward, the brain has to send executive commands to the neurons in the lumbosacral spinal cord, which then passes those commands on to the lower extremities. If the path between the brain and the lumbosacral spinal cord has been damaged or severed, those executive commands can’t land, making walking impossible.
This was the case for Gert-Jan Oskam, a man paralyzed from the hips down at 28 years old. Oskam’s accident resulted in rare yet debilitating damage to his lumbosacral spinal cord neurons, preventing his brain from shipping locomotive commands. This injury made him the ideal candidate for the brain-spine interface, or “digital bridge,” that scientists hoped would reconnect the pathways between the brain and the lumbosacral spinal cord.
The digital bridge starts with electrodes implanted into Oskam’s skull and spinal cord. These electrodes pick up on electrical signals in the brain that convey Oskam’s mobile intentions or his next movements. The scientists decoded these signals using artificial intelligence and matched them with muscle movements. The signals were sent down to the spinal cord implant, which sent signals to Oskam’s lower body.
During the first treatment, Oskam recovered his ability to twist his hips. The next several months were spent honing the interface to better predict actions related to walking, which allowed Oskam to build a healthy, natural-looking gait. Within a year, he was eventually able to use steps and ramps and get in and out of a car.
Previous attempts to restore mobility in paralyzed patients have involved constant electrical stimulation of the spinal cord. To pull this off, wearable motion sensors must predict the body’s next actions based on residual movement or compensatory strategies, like extra balancing efforts. Not only is it inconvenient to wear a motion sensor array, but the system’s calculations aren’t perfect, resulting in walking patterns that are unnatural and inconvenient for changing terrain.
Placing electrodes in the skull and spinal cord is highly invasive, so the digital bridge has its own caveats. It also isn’t suited for all spinal cord paralysis. Still, the experimental system could be encouraging for those who currently lack lower mobility and find aids like wheelchairs to be limiting or inconvenient.
