By Pat Anson, PNN Editor

A tiny wireless implant that stimulates peripheral nerves from within blood vessels shows potential as a treatment for neuropathic pain, according to a proof-of-concept study by a team of Texas researchers published in the journal Nature Biomedical Engineering.

The implants have only been tested in laboratory animals, but researchers say they could replace larger and more invasive devices currently used to treat Parkinson’s disease, epilepsy, chronic pain, hearing loss and paralysis.

The MagnetoElectric Bio ImplanT -- ME-BIT for short -- is slightly larger than a grain of rice. It’s designed to be placed in a blood vessel near the nerve targeted for stimulation. The implant requires no surgery or batteries, and draws its power and programming from an electromagnetic transmitter worn outside the body.

“Because the devices are so small, we can use blood vessels as a highway system to reach targets that are difficult to get to with traditional surgery,” said lead author Jacob Robinson, PhD, Associate Professor of Electrical and Computer Engineering at Rice University.

“We’re delivering them using the same catheters you would use for an endovascular procedure, but we would leave the device outside the vessel and place a guidewire into the bloodstream as the stimulating electrode, which could be held in place with a stent.”

The ability to power the implant remotely eliminates the need for electrical leads through the skin and other tissues. Leads used for devices like pacemakers can cause inflammation and sometimes need to be replaced. Battery-powered implants may also require additional surgery to replace the batteries.

Researchers say ME-BIT’s wearable charger could even be misaligned by several inches and still provide sufficient power and programming to the implant, without irritating surrounding tissues.

“We’re getting more and more data showing that neuromodulation, or technology that acts directly upon nerves, is effective for a huge range of disorders – depression, migraine, Parkinson’s disease, epilepsy, dementia, etc. – but there’s a barrier to using these techniques because of the risks associated with doing surgery to implant the device, such as the risk of infection,” said co-author Sunil Sheth, MD, Associate Professor of Neurology and director of the Vascular Neurology Program for McGovern Medical School at UTHealth Houston.

“If you can lower that bar and dramatically reduce those risks by using a wireless, endovascular method, there are a lot of people who could benefit from neuromodulation.”

Electrical stimulation can reduce pain when doctors target the spinal cord and dorsal root ganglia (DRG), a bundle of nerves that carry sensory information to the spinal cord. But existing DRG stimulators require invasive surgery to implant a battery pack and pulse generator.

By using blood vessels, researchers say they can place the ME-BIT implant strategically in a minimally invasive way and have more predictable outcomes.

“One of the nice things is that all the nerves in our bodies require oxygen and nutrients, so that means there’s a blood vessel within a few hundred microns of all the nerves,” Robinson explained. “With a combination of imaging and anatomy, we can be pretty confident about where we place the electrodes.

In a previous study, Robinson and his colleagues demonstrated the viability of the implants by placing them beneath the skin of laboratory rodents that were fully awake and free to roam about their enclosures. The rodents preferred to be in parts of the enclosures where a magnetic field activated the implant, which provided a small voltage to the reward center of their brains.

Researchers need to conduct more animal studies and eventually human trials before seeking FDA approval for the implants.

“We’re doing some longer-term studies to ensure this approach is safe and that the device can stay in the body for a long time without causing problems,” said Sheth, who estimates the process will take a few years.