Noninvasive Spinal Stimulation Gets a (Current) Boost

Onward’s ARC-EX delivers five times the amperage of similar devices

3 min read
view of back of person's head with white tape on their neck and hands are holding a square with different colored boxes on it

Onward Medical’s new spinal stimulation uses noninvasive electrodes to spark nerve activity and growth.


In 2010, Melanie Reid fell off a horse and was paralyzed below the shoulders.

“You think, ‘I am where I am; nothing’s going to change,’ ” she said, but many years after her accident, she participated in a medical trial of a new, noninvasive rehabilitative device that can deliver more electrical stimulation than similar devices without harming the user. For Reid, use of the device has led to small improvements in her ability to use her hands, and meaningful changes to her daily life.

“Everyone thinks with spinal injury all you want to do is be able to walk again, but if you’re a tetraplegic or quadriplegic, what matters most is working hands,” said Reid, a columnist for The Times, as part of a press briefing. “There’s no miracles in spinal injury, but tiny gains can be life-changing.”

For the study, Reid used a new noninvasive therapeutic device produced by Onward Medical. The device, ARC-EX (“EX” indicating “external”), uses electrodes placed along the spine near the site of injury—in the case of quadriplegia, the neck—to promote nerve activity and growth during physical-therapy exercises. The goal is to not only increase motor function while the device is attached and operating, but the long-term effectiveness of rehabilitation drills. A study focused on arm and hand abilities in patients with quadriplegia was published 20 May in Nature Medicine.

Researchers have been investigating electrical stimulation as a treatment for spinal cord injury for roughly 40 years, but “one of the innovations in this system is using a very high-frequency waveform,” said coauthor Chet Moritz, a neurotechnologist at the University of Washington. The ARC-EXuses a 10-kilohertz carrier frequency overlay, which researchers think may numb the skin beneath the electrode, allowing patients to tolerate five times as much amperage as from similar exploratory devices. For Reid, this manifested as a noticeable “buzz,” which felt strange, but not painful.

The study included 60 participants across 14 sites around the world. Each participant undertook two months of standard physical therapy, followed by two months of therapy combined with the ARC-EX. Although aspects of treatment such as electrode placement were fairly standardized, the current amplitude was personalized to each patient, and sometimes individual exercises, said Moritz.

The ARC-EX uses a 10-kilohertz current to provider stronger stimulation for people with spinal cord injuries.

Over 70 percent of patients showed an increase in at least one measurement of both strength and function between standard therapy and ARC-EX therapy. These changes also meant that 87 percent of study participants noted some improvement in quality of life in a followup questionnaire. No major safety concerns tied to the device or rehabilitation process were reported.

Onward will seek approval from the U.S. Food and Drug Administration for the device by the end of 2024, said study coauthor Grégoire Courtine, a neuroscientist and cofounder of Onward Medical. Onward is also working on an implantable spinal stimulator called ARC-IM; other prosthetic approaches, such as robotic exoskeletons, are being investigated elsewhere. ARC-EX was presented as a potentially important cost-accessible, noninvasive treatment option, especially in the critical window for recovery a year or so after a spinal cord injury. However, the price to insurers or patients of a commercial version is still subject to negotiation.

The World Health Organization says there are over 15 million people with spinal cord injuries. Moritz estimates that around 90 percent of patients, even many with no movement in their hands, could benefit from the new therapy.

Dimitry Sayenko, who studies spinal cord injury recovery at Houston Methodist and was not involved in the study, praised the relatively large sample size and clear concern for patient safety. But he stresses that the mechanisms underlying spinal stimulation are not well understood. “So far it’s literally plug and play,” said Sayenko. “We don’t understand what’s happening under the electrodes for sure—we can only indirectly assume or speculate.”

The new study supports the idea that noninvasive spinal cord stimulation can provide some benefit to some people but was not designed to help predict who will benefit, precisely how people will benefit, or how to optimize care. The study authors acknowledged the limited scope and need for further research, which might help turn currently “tiny gains” into what Sayenko calls “larger, more dramatic, robust effects.”

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