The RNS Stimulator consists of a small neurostimulator implanted within 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 affecting varied 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.
The FDA’s approval is supported by a three-month randomized control trial of 191 patients with drug-resistant epilepsy.
The study showed that by three months after the implanted device was turned on (active use) patients experienced a nearly 38 percent reduction in the average number of seizures per month, compared to an approximately 17 percent reduction in the average number of seizures per month in patients who had the implanted device turned off. At the end of three months, the median reduction in seizures, which reflects a more typical patient experience, was 34 percent with active use and about 19 percent with the device turned off. During the trial, 29 percent of patients with an active device experienced at least a 50 percent reduction in the overall number of seizures, compared to 27 percent for those with the implanted 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 frequent adverse events reported were implant site infection and premature battery depletion.
The RNS Stimulator is manufactured by Neuropace, Inc. of Mountain View, Calif.
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