A new medical device to treat epilepsy works like a cardiac defibrillator to detect and suppress seizures the instant they begin.

Clinical trials of the Responsive Neurostimulator System (RNS) show that the device decreases the number of monthly seizures by nearly 38 percent. The device received approval from the Food and Drug Administration on Nov. 14.

“This is the first FDA-approved brain implant for epilepsy that responds to the brain’s activity,” says Michel Berg, an associate professor of neurology at the University of Rochester Medical Center.

“For patients who are unable to control their seizures with medications or are not eligible for resective surgery, this device could provide an important treatment option.”

An estimated three million Americans suffer from epilepsy. The condition, which can be triggered by a host of different factors, results in bursts of electrical activity in the brain caused when groups of neurons fire in an abnormal pattern. The resulting seizures can vary in length and severity.

While most individuals with the condition are able to manage their symptoms with one or more antiepileptic drugs, for a significant portion of people with epilepsy these medications are either not effective or result in intolerable side effects. Some of these patients are candidates for surgery, which removes the region of the brain where the seizures originate.

Like a cardiac defibrillator

However, when the seizures come from several different spots or are located in an area of the brain that serves an important function, such as language processing or motor control, resective surgery is not possible. For patients who have run out of traditional medical options, the device may be an effective way to control their seizures.

The implantable device is designed to suppress seizures before symptoms appear. The device functions in a manner akin to implantable cardiac defibrillators, which detect abnormal heart rhythms and then deliver electrical stimulation to correct them.

The RNS is surgically implanted under the scalp and connected to one or two leads—insulated wires with electrodes at the end—that are placed either on the surface of the brain or are guided into the brain in the area where the seizures are determined to originate.

It continuously monitors the patient’s brain waves and when seizure activity is detected, the device instantly delivers a mild, brief electrical stimulation that suppresses the seizures.

“The RNS system is not only a technological breakthrough, but the device is an important new tool that could help patients control their seizures and, ultimately, improve their quality of life,” says James Fessler, director of URMC’s Strong Epilepsy Center.

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