Epilepsy affects 3 million people in the US, making it the third most common neurological disorder in the country. In a move that may offer relief for some patients, the FDA has approved a skull implant that helps reduce the frequency of seizures in patients with drug-resistant epilepsy.

The device is known as an RNS Stimulator, a neurotransmitter that sends electrical impulses to areas of the brain where seizures are believed to originate. Seizures occur when groups of neurons fire abnormally. This device is able to detect when seizure-causing electrical signals are happening in the brain, and fires impulses of its own in order to help regulate brain activity.

The RNS Stimulator's efficacy is supported by nearly a decade of research. NeuroPace, the implant's manufacturer, worked with 256 patients — some for eight years — to determine the device's therapeutic benefits. In a three-month trial of 191 patients with drug-resistant epilepsy, patients with the implant turned on experienced a 37.9 percent decrease in their seizures over the course of a month. During a two-year follow-up phase, patient still showed reduced seizure frequency.

A panel of experts convened by the FDA unanimously recommended approving the RNS Stimulator in February.

The RNS Stimulator isn't only the latest device to be used for treating debilitating brain disease. 100,000 people in the US currently live with brain stimulation devices to treat such illnesses as dystonia and Parkinson's disease, especially when medications stop working.