People who suffer severe epileptic seizures may one day be able to control or even prevent them with an electronic device implanted directly into the brain. An oncoming seizure would trigger the targeted release of a brain-signaling chemical to stop the seizure in its tracks, according to a new study published in Science Advances. The device has only been tested on mice so far, but the results look promising.

The brain is a noisy place, with tens of billions of neurons organized into a highly complex, interconnected network. Neurons fire and send electrical signals to neighboring neurons, encouraging them to fire in turn, thereby helping spread signals throughout the brain. In an epileptic seizure, that normal brain activity goes into overdrive, creating a cascading snowball effect that interferes with motor control and can lead to loss of consciousness.

Epilepsy is usually treated with anti-seizure drugs. These can have serious side effects, however, and roughly three out of 10 patients don't respond at all to the treatment. In those cases, brain implants may be the best option, such as Neuropace's brain implant, which earned FDA approval for clinical use for epilepsy in 2013.

Using one of the Neuropace-style devices involves implanting electrodes directly into the brain to deliver pulses of electrical activity whenever a seizure starts to develop. It regulates brain activity much like a pacemaker regulates heart rhythm by sending its own signals regardless of what the rest of the brain might be doing. The implant is not without risks, since it requires invasive, risky brain surgery. But for someone suffering from debilitating seizures, it can be an acceptable tradeoff.

The new brain implant, developed by a team of British and French scientists, works a bit differently. When a seizure is detected, it uses a tiny ion pump to send a neurotransmitter directly to the source of the seizure, using electric fields to guide the chemical out of the device (and also to control the dosage). This tells the neurons to stop firing and effectively ends the seizure—at least in mice. Humans aren't likely to have access to the treatment any time soon.

“In a sense, we can communicate with cells in their native language.”

The researchers found they only needed small doses to prevent seizures in mice, and because the device uses natural neurotransmitters, the brain absorbed them quickly. That combination of lower dosage and swift uptake may offer a distinct advantage over electrical-stimulation brain implants. According to lead author Christopher Proctor, a postdoc at the University of Cambridge, electrical stimulation is not particularly targeted, and it may influence many different areas of the brain at the same time and in different ways. So patients may experience dramatic shifts in mood or behavior.

"The advantage of [targeted] chemical delivery is that the effect on cells is very specific," Proctor said. "The neurotransmitters used in this study have well-understood effects on cells, and cells already use them to communicate with each other. So, in a sense, we can communicate with cells in their native language."

DOI: Science Advances, 2018. 10.1126/sciadv.aau1291 (About DOIs).