Smaller Than a Grain of Rice, Tiny Implants Buzz Away Pain and Someday Perhaps Sorrow

These tiny implantable nerve stimulators are meant to stimulate peripheral nerves to treat chronic pain and other neurological disorders. But eventually, devices this small -- or smaller -- will fit near or within the brain, to deliver tiny currents of healing and eventually pleasure.

Like some cochlear implants and other medical devices, the implant is powered with radio-frequency transmission: radio waves transmitted by the external coil generate a magnetic field in the internal coil, which powers the electrodes. Adopting technologies from the rapidly advancing RFID world has allowed the researchers to further shrink the device. "Instead of trying to transfer energy from two coupled antennas to do telemetry, which is a common approach for medical devices, RFID is geared to have very small transponders, so you don't need a large coil," says Joseph Pancrazio, a program director at the National Institute for Neurological Disorders and Stroke, a government funding agency, in Bethesda, MD, that has given the company small business loans.

The research is still in a very early stage. Researchers have developed a prototype device, which they are testing in rats. The device can effectively stimulate peripheral nerves in rats, although it's not yet clear whether the electrical stimulation alleviates chronic pain. (Scientists assess chronic pain in rats by recording how much the animals eat; a rat in pain won't eat as much.)

Some scientists are skeptical that the device will be powerful enough to deliver a therapeutic level of stimulation. "The main limitation of any electronic device small enough to be injected into the body is that it must receive enough power to operate its circuitry and provide the required stimulation parameters," says Gerald Loeb, director of the Medical Device Development Facility at the University of Southern California, in Los Angeles. Loeb has also developed an injectable radio-powered microstimulator, which he says has encountered substantial limitations in range and power.

"We believe we can do it with less power," says Scott Armstrong, MicroTransponder's chief technical officer. However, he declined to give further details of the technology for proprietary reasons. _TechnologyReview

If not now, soon. It is quite clever of the researchers to use RFID technology for implantable nerve stimulators. Such an approach could be easily transferred to intracranial implants-without-antennas, as long as the power signal was able to safely penetrate the skull without damaging intervening tissues. Otherwise, antennas that are colour-matched to the person's hair could transmit the power signal to the implant. Advances in biocompatible materials will make such long-term implants viable.

Needless to say, technology that allows for miniaturisation of implants should also allow for simultaneous placement of multiple, strategically-placed implants that could communicate with each other, and coordinate for sophisticated neuro-stim routines.

Cross-posted at Al Fin Longevity