The U.S. Food and Drug Administration (FDA) today approved a brain implant designed to treat epilepsy. The implant is now approved for use in the U.S. to help reduce the frequency of epilepsy-related seizures for patients who haven’t responded to seizure medications.

The implant is called the RNS System and is manufactured by a company called Neuropace. I consists of a neurostimulator that is implanted within a patient’s skull, then connected to two electrodes that are placed on or inside a patient’s brain in areas where doctors believe epilepsy seizures occur. The neurostimulator then provides a normalizing burst of electrical stimulation when it detects electrical activity consistent with an oncoming seizure.

“The neurostimulator detects abnormal electrical activity in the brain and responds by delivering electrical stimulation intended to normalize brain activity before the patient experiences seizure symptoms,” said Christy Foreman, director of the Office of Device Evaluation at the FDA.

Approval for the device was based on a three month clinical trial in which 191 epilepsy patients who had not responded to seizure medications were implanted with the device. Patients participating in the trial were shown to have n average of around 38% fewer seizures each month.

Abnormal electrical signals in the brain are known to cause epilepsy. People with the disorder often suffer from odd physical behaviors or seizures. According to the FDA around 3 million people in the U.S. suffer from epilepsy, and almost 200,000 Americans will be diagnosed each year.