INDIANAPOLIS — Electrical stimulation devices implanted in the brain not only bring significant relief to many epilepsy patients but appear to become more effective over time, according to research studies published earlier this year.
In reviews of patient outcomes five years after surgery for two systems — one approved for use in the U.S. and the other under Food and Drug Administration review — scientists reported that the devices provided substantial relief to many patients identified as “refractory,” meaning that multiple drugs, and sometimes other surgical interventions, had not helped them. Moreover, the national studies suggest that the benefits grew stronger over time.
For both devices, the median reduction in the number of seizures five years after the devices were implanted was 66 percent to 69 percent, a significant impact for patients who had been experiencing multiple serious seizures every month.
“This is a significant advance for patients with severe partial epilepsy who are refractory to other treatments and are not candidates for resective epilepsy surgery,” said Vicenta Salanova, M.D., professor of neurology and director of the Comprehensive Epilepsy Program at Indiana University School of Medicine.
About 3 million people in the United States have epilepsy resulting in seizures, which are disruptions in the electrical signaling in the brain that can cause a broad range of symptoms including loss of consciousness and convulsions. About one-third of people with epilepsy are resistant to medical treatment. Resective epilepsy surgery to remove the area of the brain where seizures begin is an option for some who are resistant to drug treatment, but such surgery is not an option for others.
For such patients, implanted devices can offer hope. The two devices reviewed recently use different mechanisms. One, called the RNS Stimulator from NeuroPace Inc., uses electrodes implanted in or near the location in the brain where a patient’s seizures start. When abnormal electrical patterns resembling the onset of a seizure are detected, the RNS Stimulator sends an electrical charge to the seizure focus to prevent it from developing into a seizure. The device was approved for use in the United States in 2013.
The five-year results, from 230 patients, of the NeuroPace study were reported in a paper published in February in the journal Neurology co-authored by Dr. Salanova with contributions by six additional IU School of Medicine researchers.
The second device studied, made by Medtronic Inc., uses bilateral depth electrodes placed in the thalamus, a region deep inside the brain with connections to areas of the brain where epileptic seizures often begin. Instead of responding to signs of a seizure, a controller placed under the skin in the chest sends regular electrical signals to the thalamus in hopes of preventing a seizure from spreading. The Medtronic device has been approved by regulators in Europe, Canada and Australia but it remains an experimental device in the U.S.
The long-term results of the thalamic stimulation treatment with the Medtronic device, known as the Stimulation of the Anterior Nucleus of the Thalamus for Epilepsy (SANTE) trial, were reported in a March 10 paper, also in the journal Neurology, for which Dr. Salanova was the first author and IU physicians Nicholas Barbaro, M.D., Thomas Witt, M.D., and Robert Worth, M.D., were among the 27 additional authors from multiple research sites.
While relatively few patients had seizures eliminated for any significant amount of time, in the five years of follow-up 16 percent of patients were seizure-free for at least 6 months.
Researchers noted that continued improvement over time has been observed in brain implants for other conditions as well as epilepsy, but it’s not known why that occurs.
While providing relief to many participants in the studies, the devices were not free of side effects. Problems such as implant site pain, tingling or vibration sensations were reported. In the SANTE trial the most common serious adverse event through five years of follow-up was implant site infection of 10 percent.
The two studies were funded by the respective device manufacturers.
Additional IU School of Medicine faculty participating in the epilepsy research were Nicholas Meridith Runke, M.D., and Drago Sabau, M.D.