The U.S. Food and Drug Administration has approved a device to help reduce the frequency of seizures in epilepsy patients who have not responded well to medications in the past.

The NeuroPace RNS Stimulator consists of a small neurostimulator implanted in the skull under the scalp. The neurostimulator is connected to one or two wires (called electrodes) that are placed where the seizures are suspected to originate within the brain or on the surface of the brain.

“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 in the FDA’s Center for Devices and Radiological Health.

Epilepsy produces seizures that can affect a variety of mental and physical functions. Seizures happen when clusters of nerve cells in the brain signal abnormally, which may briefly alter a person’s consciousness, movements or actions. According to the Epilepsy Foundation, epilepsy affects nearly 3 million people in the United States and is the third most common neurological disorder, after Alzheimer’s disease and stroke. Approximately 40 percent of people with epilepsy are severely affected and continue to have seizures despite treatment.

This recent FDA approval is supported by a three month randomized control trial that included 191 patients with drug resistant epilepsy.

The clinical trial study showed that within three months after the implanted device was activated, patients experienced an almost 38 percent reduction in the average number of seizures they experienced each month, in comparison to an almost 17 percent reduction in the average number of seizures each month in patients who had the implanted device deactivated. At the end of three month trial period, the median reduction in seizures was 34 percent with active use and about 19 percent with the device turned off. Also, 29 percent of patients with an active device experienced at least a 50 percent reduction in their overall number of seizures, compared to 27 percent for those with the device turned off.

During a two-year follow-up phase (unblinded), data demonstrated a persistent reduction in seizure frequency.

Patients with RNS Stimulators cannot undergo magnetic resonance imaging (MRI) procedures, nor can they undergo diathermy procedures, electroconvulsive therapy (ECT) or transcranial magnetic stimulation (TMS). The energy created from these procedures can be sent through the neurostimulator and cause permanent brain damage, even if the device is turned off.

The most frequently reported adverse events during the clinical trial were implant site infection and premature battery depletion.