NeuroPace is generally seen as the furthest along of a handful of neural implant efforts around the world. "The field is very much in the beginning stages of sensing and algorithm development, and the devices are all in investigation stages doing pilot clinical trials," said Tim Denison, a technical fellow at Medtronic.
Denison has worked for several years developing the chips for Medtronic's Activa PC+S device, which was implanted in its first trial patient earlier this year. About 20 teams around the world will eventually implant a couple hundred of the devices over the next two to four years as part of its trials.
NeuroPace is unique in being a closed-loop system, automatically applying therapy based on sensed brain wave patterns, Denison said. Medtronic's device is unique in continuing to sense brain wave activity even while it sends out therapeutic signals thanks to a custom amplifer design and other techniques.
"We're taking advantage of radio principles to tune into brain waves just like you would a radio station, rejecting bands where stimulation sits," Denison explained. "We maintain microvolt resolution of neural activity even in presence of stimulation signals on the order of a volt," he added.
Denison of Medtronic shows an early prototype board.
Not everyone is convinced deep brain stimulation will become a huge new field.
"I have a jaundiced view, primarily because of the brain damage that is caused not only by the placement of the stimulation and sensing electrodes but also from the milliampere levels of stimulation," said Mir Imran, a serial entrepreneur and investor in implants who developed one of the first defibrillators. "Depending on the location of the electrode leads/stimulation, the brain damage can result in cognitive impairment, memory loss, and other deficits," said Imran.
However, he was quick to add that "a few patients with incessant seizures who are refractory to drug therapy might get some benefit from this therapy, and it may be a better option than brain resection surgery for these patients."