Neuroprosthetics Applications Continue to Evolve

by James Cavuoto, editor

March 2025 issue

The field of neuroprosthetics has seen a number of advancements in recent months, as investigators at research institutions in the U.S. and Europe have reported progress, and as device firms active in the space have announced product enhancements and other commercialization milestones.

On the research front, European and American investigators reported breakthroughs in two areas impacting individuals with spinal cord injury: restoring locomotion and restoring sensation. Rehabilitation robotics—devices that guide movement during therapy—have improved training for those with SCI, but their effectiveness remains limited. Without active muscle engagement, robotic-assisted movement alone does not sufficiently retrain the nervous system.

A team at .NeuroRestore, led by Grégoire Courtine and Jocelyne Bloch, developed a system that seamlessly integrates an implanted spinal cord neuroprosthesis with rehabilitation robotics. The researchers’ device delivers well-timed electrical pulses to stimulate muscles in harmony with robotic movements, resulting in natural and coordinated muscle activity during therapy. The neuroprosthetics innovation leveraged the robotic expertise of Auke Ijspeert’s lab at EPFL. This advancement not only enhances immediate mobility but also fosters long-term recovery.

“The seamless integration of spinal cord stimulation with rehabilitation or recreational robotics will accelerate the deployment of this therapy into the standard of care and the community of people with spinal cord injury,” said Courtine. This adaptability ensures that rehabilitation professionals can incorporate this technology into existing rehabilitation protocols worldwide. Combining therapies also presents significant challenges, as each requires precise synchronization. Spinal cord stimulation strategies must be modulated in both space and time to match the patient’s movement, and integrating them with widely used robotic rehabilitation systems requires a flexible and adaptable framework.

The technology relies on a fully implanted spinal cord stimulator that delivers biomimetic electrical epidural stimulation. Unlike traditional functional electrical stimulation, this method activates motor neurons more efficiently by mimicking natural nerve signals.

The researchers integrated electrical epidural stimulation with various robotic rehabilitation devices—including treadmills, exoskeletons, and stationary bikes—ensuring that stimulation is precisely timed with each phase of movement. The system uses wireless sensors to detect limb motion and automatically adjust stimulation in real time, allowing for a seamless user experience.

In a proof-of-concept study involving five individuals with spinal cord injuries, the combination of robotics and electrical epidural stimulation resulted in immediate and sustained muscle activation. Not only did participants regain the ability to engage muscles during robotic-assisted therapy, but some also improved their voluntary movements even after the stimulation was turned off.

The study also showed the potential of this approach beyond clinical settings, as participants used the system to walk with a rollator and cycle outdoors, validating its real-world impact.

Restoring the sense of touch is an important goal for neuroprosthetics researchers. Touch sensation involves a complex network of nerve fibers running from the skin to the brain. If any link in this chain is broken, such as from the loss of a limb, a spinal cord injury, or a stroke, this sense can be disrupted or lost.

A new study published in Science, paves the way for complex touch sensation through brain stimulation, whilst using an extracorporeal bionic limb, that is attached to a chair or wheelchair.

The researchers, who are all part of the U.S.-based Cortical Bionics Research Group, have discovered a unique method for encoding natural touch sensations of the hand via specific microstimulation patterns in implantable electrodes in the brain. This allows individuals with SCI not only to control a bionic arm with their brain, but also to feel tactile edges, shapes, curvatures and movements, that until now have not been possible.

“In this work, for the first time the research went beyond anything that has been done before in the field of brain-computer interfaces; we conveyed tactile sensations related to orientation, curvature, motion and 3D shapes for a participant using a brain-controlled bionic limb. We are in another level of artificial touch now. We think this richness is crucial for achieving the level of dexterity, manipulation, and a highly dimensional tactile experience typical of the human hand,” said Giacomo Valle, from the University of Chicago and Chalmers University of Technology in Sweden, who was lead author on the paper.

The team placed ICMS electrodes into the somatosensory cortex in two participants. Both had spinal cord injuries that disrupted communication between the brain and the hand. The researchers used recent breakthroughs in understanding the structure and organization of the somatosensory cortex to precisely place the electrodes. They then tested the ability of the electrodes to mimic the electrical signals that represent the sense of touch.

When the researchers activated the electrodes in a pattern designed to evoke the sensation of touching an edge, the participants reported feeling edge-like sensations. Other stimulation patterns let participants identify simple shapes that would normally require feedback from several different fingers at the same time. Some patterns mimicking multiple fingers gave participants complex touch sensations, such as grasping a can or holding a pencil or a ball.

This brain activation was fast enough to enable real-time feedback to and from bionic limbs. The electrodes could also evoke the sensation of motion on the skin in four different directions. In a final experiment, one participant was able to use the electrodes to communicate with a stand-alone bionic arm and steer a wheel in response to the sensations of movement provided via the implanted electrodes.

More work will be needed before such systems could be tested in larger studies, including the development of smaller and more powerful sensors for bionic limbs.

The Cortical Bionics Research Group is made up of three north American Universities: University of Pittsburgh, University of Chicago and Northwestern University. The mission of the Cortical Bionics Research Group is to build next-generation intracortical BCIs that enable dexterous control of bionic hands by people with paralysis or amputation.

On the commercial front, ONWARD Medical, the Eindhoven, Netherlands manufacturer of neurorehabilitation systems, announced the first human implant of its investigational ARC-IM lumbar lead. This milestone procedure was performed earlier this month, by Jocelyne Bloch, chief of neurosurgery at Lausanne University Hospital in Switzerland. The company previously announced first-in-human use of the ARC-IM thoracic lead in 2023. The thoracic lead is optimized for placement in the thoracic region of the spinal cord; it will be used as part of the investigational ARC-IM system in the company’s planned Empower BP pivotal study to address blood pressure instability after SCI.

The new lumbar lead is specifically designed for placement in the lumbar region of the spinal cord, the optimal location for therapies targeting restoration of standing, stepping, and lower limb mobility after SCI. It will be used in ongoing clinical feasibility studies with and without an implanted BCI.

Also this month, ANEUVO, the Los Angeles, CA manufacturer of neurorehabilitation systems, announced the launch of the ASPIRE Home Study, the next phase of clinical research for its ExaStim neuromodulation device. The study aims to alleviate a common issue for individuals living with chronic SCI, namely the inability to access clinic-level therapies in a home setting.

The study, which will focus on improving upper limb motor function, will enroll an estimated 30- to 35 participants who were participants of the initial ASPIRE trial. Conducted as a single-arm, prospective, observational study and expected to take six months from enrollment to completion, all participants will receive ExaStim therapy for the entire study duration.

The clinical teams at Marquette University College of Health Sciences in Milwaukee, Spaulding Rehabilitation Hospital in Boston, Craig Hospital in Denver, Kennedy Krieger Institute in Baltimore, and TryAbility Neurorecovery Center in Chicago will collect the study data.

Another Los Angeles firm, SpineX, announced a strategic relationship with two Asian firms to distribute products for the paralysis community. The two Indian firms, Vivatronix Technologies Pvt. Ltd. and ImagineHealth Co., Ltd., will offer SpineX’s noninvasive xStep spinal cord stimulator to international markets. The system is designed for at-home use—making it easier, more convenient, and cost-effective for patients to actively participate in their recovery. This device aims to enhance motor function, improve bladder control, and significantly improve the quality of life for patients suffering from complex neurological conditions such as cerebral palsy, neurogenic bladder, SCI, multiple sclerosis, and stroke.

In another development, investigators at the University of Utah’s NeuroRobotics Lab entered into a contract with startup firm Biologic Input Output Systems to enable control of DEKA’s Luke arm just by thinking. Lab director Jacob George serves as chief scientist for the startup firm. The team has an IDE early feasibility study underway with eight enrollees.

The clinical trial is for transradial amputees. To enable the thought-based control of a robotic arm, patients will have Utah slanted electrode arrays and intramuscular electromyographic recording leads implanted into their residual arm nerves and muscles. After being fitted with the device in the lab and undergoing preliminary tests, the participants will then have the opportunity to take the device home for one year, and potentially longer.