AI-based ‘digital bridge’ enables paraplegic patient to walk

A “digital bridge” that uses artificial intelligence to decode brain signals has enabled a paraplegic patient to walk just by thinking about moving his legs, boosting hopes that the neurotechnology could eventually help millions of people overcome disabilities.

Swiss researchers implanted an electronic device in the patient’s skull on top of the region of the brain responsible for controlling leg movements. Using algorithms based on adaptive AI methods, “movement intentions are decoded in real time from brain recordings”, said Guillaume Charvet, head of brain-computer interface research at French public research body CEA.

These signals are then transmitted wirelessly to a neurostimulator connected to an electrode array over the part of the spinal cord that controls leg movement below the injury site, said Jocelyne Bloch, the project’s neurosurgeon.

Researchers at École Polytechnique Fédérale de Lausanne (EPFL) and Swiss hospitals published their findings in Nature on Wednesday. The breakthrough will enable doctors to bypass damaged nerves and boost the treatment of a range of neurological disorders including strokes, the researchers said, though they caution that much research and development will be required to miniaturise and enhance the technology, cut production costs and carry out extensive clinical trials.

Gert-Jan Oskam, the first patient fitted with the digital bridge, said he had regained natural control over the movement of his limbs, enabling him to walk and climb stairs — or just share a beer with friends standing at a bar.

“This simple pleasure represents a significant change in my life,” said Oskam.

The EPFL team previously used a more complex procedure to restore mobility to people paralysed by spinal cord injury. Patients specified their desired movements — for example, standing, walking or pedalling — by pressing keys on a small tablet computer, which then transmitted instructions to a series of electrodes implanted in the lower spinal cord. These stimulated nerve cells to initiate movement in the appropriate muscles.

Oskam, a Dutch man whose spine was injured 11 years ago in a bike accident, was upgraded to the new digital bridge from the previous system. “This feels radically different,” he said. “Before I felt that the stimulation was controlling me, now I am controlling the stimulation myself. I can take steps that feel natural.” The new system does not rely on instructions from an external computer.

As Oskam used the digital bridge, his brain and nervous system adapted to it, forming new connections that enabled him to walk with crutches even when the spinal implant was switched off.

Although the digital bridge has been tested only on Oskam, the researchers are about to extend the clinical trial, initially to three new patients and then many more. They expressed confidence that the technology would work in other applications if the position of implants was altered. Hand and arm mobility could be restored in people with paralysed upper limbs and disability reduced in stroke patients, for example.

“The concept of a digital bridge between the brain and spinal cord augurs a new era in the treatment of motor deficits due to neurological disorders,” the Nature paper concludes.

Onward Medical, a company based in the Netherlands and founded by Bloch with EPFL neuroscience professor Grégoire Courtine, is commercialising the digital bridge technology.