Anti-seizure medications aren’t always effective at stopping or reducing seizures in epilepsy patients. Fortunately, those patients have access to another option: responsive neurostimulation (RNS).
What is responsive neurostimulation, and how does it work?
We asked University of Minnesota Health Epileptologist Sima Patel, MD, who cares for epilepsy patients at the University of Minnesota Health Clinics and Surgery Center and MINCEP Epilepsy Care in St. Louis Park, to tell us more about the innovative technique. Patel shared five things prospective patients should know about responsive neurostimulation.
Responsive neurostimulation, which received FDA approval in 2013, is a surgically implanted device developed for the treatment of epileptic seizures that are not controlled by medication. Neurosurgeons implant electrodes directly into targeted regions of the brain where the patient’s seizures are known to originate. Those electrodes measure and monitor brain activity, searching for abnormal patterns associated with the onset of a seizure.
“When it detects seizure patterns, it will, within a brief period, deliver a small amount of electrical stimulation to disrupt the abnormal brain activity, stopping a seizure or shortening before it starts and resetting the brain to its normal patterns,” Patel said. “The device is similar to a pacemaker for your heart. A pacemaker detects an abnormal rhythm and delivers an electrical stimulation to return the heart rhythm back to baseline.”
The device is powered by a battery and micro-processor, both of which are also implanted into patient’s skull.
Patients with frequent, disabling seizures may be eligible to receive responsive neurostimulation if they continue to experience seizures despite the use of anti-seizure medications, and are not candidates for surgical resection.
“These are patients who have tried adequate doses of at least two different anti-seizure medications, both of which have failed to control their seizures in a meaningful way,” Patel said. “They usually have multiple seizures each month that affect their quality of life.
Before being equipped with the device, patients must undergo comprehensive epilepsy testing to identify seizure onset zone. The RNS electrodes are then placed in the brain where patient’s seizures are known to originate from.
“Patients who have severe epilepsy and are drug resistant should always get an opinion from a Level 4 surgery center,” she added. “This is very critical because a lot of times patients feel there is no hope nor any options. It is always helpful to learn about new technology and then make an informed medical decision.”
Because responsive neurostimulation involves brain surgery to implant the device, there are associated risks. With brain surgery, there is a small risk of infection, bleeding, pain and neurological impairment following the procedure, Patel said. In a small percentage of patients, RNS does not prove effective at stopping seizures.
Once the responsive neurostimulation system is implanted and activated, however, there are not any significant side effects. Some patients might experience minor discomfort during the initial programming and adjustment of the device. Doctors will work the patient to reduce or change the device settings to eliminate any problems and ensure the patient is comfortable.
Studies have shown that epilepsy patients using the RNS system experience meaningful improvements in seizure control, Patel said. The therapy, when administered with anti-seizure medications, led to 44-percent reduction in patient-reported seizures after one year, a 53-percent reduction after two years and a 48- to 66-percent reduction beyond that.