So far, paraplegia cannot be cured. However, a digital interface between the brain and spinal cord could in the future give paralyzed patients at least some of their ability to move. In a pilot study, the implant enabled a patient who had been paralyzed for ten years to walk and stand on his own again - albeit with crutches. In addition, the stimulation provided by the implanted electrodes supported the regeneration of the damaged spinal cord, so that the patient can now walk even when the device is switched off.
When we want to move our limbs, our brain sends the appropriate signals via the spinal cord to the muscle groups involved. If this connection is damaged - for example due to an injury to the spinal cord after an accident - those affected can no longer move any limbs below the damaged area: They are paraplegic. It has not yet been possible to regenerate the injured nerve fibers, even if there are already experimental approaches. To help those affected, researchers are also working on tools such as exoskeletons, brain-computer interfaces and electrical bridging of the damaged area.
Intuitive movement control restored
A team led by Henri Lorach from the Swiss Federal Institute of Technology in Lausanne (EPFL) has now presented a new system in the journal "Nature". "We have developed a wireless, digital bridge between the brain and spinal cord that restores natural control over lower limb movements to stand and walk on complex terrain after paralysis due to spinal cord injury," reports the research team.
In a clinical pilot study, the researchers implanted the system in a patient who was 38 years old at the start of the study and had been paraplegic for ten years after injuring his cervical spine in a bicycle accident. He had previously taken part in a study aimed at stimulating the regeneration of the spinal cord through electrical stimulation. As part of this previous study, the patient had electrodes implanted in his spinal cord that enabled him to walk again with the help of a rollator. However, despite continued use of the stimulation, his recovery made no further progress, so he decided to try the new system.
Independent application in everyday life
To do this, the researchers first used brain scans to investigate which regions of the brain are particularly active when the patient imagines moving their legs. At these points in the motor cortex, they implanted two small plates, each with 64 electrodes that record the signals. "Thanks to algorithms based on methods of adaptive artificial intelligence, the movement intentions are decoded in real time from the brain recordings," explains co-author Guillaume Charvet from the University of Grenoble in France. Training for just a few minutes was enough.
The information about the intended movement is sent wirelessly to the implant in the patient's spinal cord, where it is converted into sequences of electrical impulses. These stimulate the nerves in the spinal cord to activate the correct leg muscles for the desired movement. After a supervised training phase in the laboratory, the researchers equipped the patient with a mobile system that he can use independently in everyday life. "The patient reports that the brain-spinal cord interface allows natural control over the movements of his legs to stand, walk, climb stairs and even traverse complex terrain," write the research team.
Implant promotes neurological recovery
The researchers and the patient also found another positive effect: “The neurorehabilitation supported by the interface also improved neurological recovery. The patient regained the ability to walk with crutches even when the device was off," the team reports. "These results suggest that establishing a continuous connection between the brain and spinal cord promotes the reorganization of the remaining neural pathways that connect these two regions under normal physiological conditions."
Although the system has only been tested on a single patient so far, the research team believes it could find widespread use in people who are paralyzed - both after spinal cord injuries and after a stroke. "The concept of a digital bridge between the brain and spinal cord promises a new era in the treatment of motor deficits due to neurological disorders," say the authors.
Source: Henri Lorach (Ecole Polytechnique Fédérale de Lausanne, EPFL, Geneva, Switzerland) et al., Nature, doi: 10.1038/s41586-023-06094-5