Tiny Implanted Wireless Device Could Be the Next Thing in Brain Stimulation

An implanted wireless device that is smaller than a cubic millimeter may be the future for deep brain stimulation in Parkinson’s disease.

A team of engineers at the non-profit Draper Laboratory built such a device, then tested it in animals to prove that it works.

Draper’s team and collaborators at Massachusetts General Hospital, the Massachusetts Institute of Technology and the University of Texas published a study in the journal Frontiers in Neuroscience showing that the concept is viable.

“Building a device small enough to be injected into the human body that can operate wirelessly and does not require surgery every time it needs a new battery is a real challenge,” Daniel Freeman, a senior research engineer and electrophysiologist at Draper, said in a press release. The company is based in Cambridge, Massachusetts, the same city as MIT.

Parkinson’s patients already used deep brain stimulation to control their symptoms. But the devices are far from optimal. The radio-frequency-powered stimulators are often large and may require surgery to change batteries.

In their article, “A Sub-millimeter, Inductively Powered Neural Stimulator,” the team described how they developed a stimulator smaller than half a cubic millimeter.

Crucial to the small size was encasing the device in a medical-grade resin. Current stimulators have titanium or ceramic capsules, making the device bulky. The team also reduced the number of electronic components in the stimulator they created.

The device is 2.5 millimeters long — about a tenth of an inch. Its wires are 0.5 millimeters in diameter. Other radio-powered wireless stimulators are five times larger.

Draper’s devices includes a coil to receive power, a capacitor to tune the frequency of the receiver,  and a diode to fine-tune the radio-frequency signal that generates the nerve stimulation.

When the team tested the device on the sciatic nerves of rats, it stimulated the animals’ movement.

“We believe the device could be used in any number of applications in the peripheral nervous system,” Freeman said. The peripheral system is the one outside the brain and spinal cord.

Although the proof-of-concept study focused on peripheral nerves, the research team said it could generate deep brain stimulation as well.

The team needs to address various challenges before the device is ready for humans. For example, if a person develops an infection, it may be difficult to remove the implant.