A team of researchers from Feinstein Institutes for Medical Research achieved what until now was considered impossible: restoring hand function and tactile sensation in a person with complete quadriplegiawith improvements that persist more than two years after the end of the intervention.
The study was published this week on the cover of Nature Medicine and represents a milestone in the history of brain-computer interfaces.
The system, called «doble bypass neural»combines brain implants with artificial intelligence and electrical stimulation of the spinal cord, as explained by the institution in a statement.
Unlike previous technologies, it doesn’t just compensate for injury while the device is active: it physically reorganizes damaged nerve circuits, a process known as neuroplasticity.
The clinical trial participant is Keith Thomasa 48-year-old man from Massapequa, New York, who was left with complete tetraplegia after a diving accident. When she joined the study, just 13 months after her injury, she couldn’t raise her arms to her face, hold objects, or feel anything in her hands or wrists.
How the system works
The procedure began with a 15-hour open-skull surgery in which five microelectrodes were implanted in Thomas’ brain: 128 channels recorded signals from the motor cortex and 96 channels from the sensory cortex.
Machine learning algorithms decode movement intentions from those signals with up to 84.6 percent accuracy, sustained for five months without the need for recalibration.
When Thomas thinks about moving his hand, artificial intelligence It translates those neural signals into electrical stimulation patterns that activate the muscles of the forearm.
At the same time, force sensors integrated into a 3D printed orthosis measure pressure during grips and send signals to the sensory cortex, generating the perception of touch in specific areas of the hand.
The precision of the system is remarkable. Thomas managed to pick up and lift empty eggshells without breaking them on 87 percent of attempts. And it was able to do so while holding conversations, indicating a significantly lower cognitive load than previous systems.
Strength, feel and long-lasting recovery
Over 35 weeks of intervention, Thomas recorded statistically significant increases of 86 percent in right arm strength and 62 percent in left arm strength. A man who at the beginning of the study could not bring his hands to his face managed to scratch his nose and wipe his mouth independently.
To restore tactile sensation, the team developed a technique called «cortical mirror»which involves recording brain activity patterns during imagined touch and «playing them back» through electrical stimulation of the sensory cortex while simultaneously stimulating the spinal cord and skin.
After approximately 25 weeks of this procedure on his right wrist, Thomas regained the ability to feel touch in an area that had been completely numb since his injury.
The improvements did not disappear at the end of the study. «Notably, in a recent follow-up, those gains were found to persist after more than two years. This is incredibly encouraging,» he said. Chad BoutonPh.D., professor at the Institute of Bioelectronic Medicine at the Feinstein Institutes and corresponding author of the study.
Thomas himself described the impact on his daily life. «Being able to feel my sister’s hand, pet my dog and feel her fur – those experiences that the injury took away from me have been restored,» he said.
«But beyond the studio sessions, I can now scratch my face and wipe my eyes independently. Technology gave me back both connection and sense of self,» he added.
Clinical scope and next steps
Spinal cord injury affects about 15 million people worldwide, more than half of whom suffer from tetraplegia with involvement of the arms and hands. Recovering manual function is the number one priority for those living with tetraplegia, above walking or regaining sphincter control, although until now this recovery was extremely rare in complete cervical injuries.
«This research has potential for millions of patients and opens possibilities for future clinical applications that could help hundreds of thousands of people living with paralysis,» Bouton said.
«This approach is a new way to treat severe paralysis: we are not only avoiding injury, but we are actually rewiring the nervous system,» he said.
Kevin J. Traceyphysician, president and CEO of the Feinstein Institutes, considered that the work «opened up new therapeutic possibilities for restoring function after injuries to the brain and nervous system.» The system has already been included in TIME magazine’s Hall of Fame of Best Inventions, which recognizes the 25 most influential inventions of the last quarter of a century, and was also part of that publication’s list of Best Inventions of 2024.
The team is now working on an expansion of the clinical trial to include participants with different levels of spinal cord injury and potentially other neurological conditions such as stroke damage.
In addition, they have already completed an additional study in which Thomas used his brain implant to help another participant with spinal cord injury move his hand, while he perceived tactile sensations when the other touched different objects, a paradigm that the team calls «interhuman neural bypass.»
