Responsive neurostimulation device or RNS system is a neurostimulation system designed to prevent epileptic seizures. The RNS device is implanted while connected to leads that are placed in up to two areas where seizures begin. The device monitors brain activity in order to detect abnormal patterns, and in response delivers electrical pulses in an attempt to prevent seizures. The RNS System was approved by the US FDA in 2013 to treat adults with partial onset seizures that are not controlled by medications. As of March 2017 over 1,000 patients have been implanted with the RNS System.
Method
The RNS System continuously monitors brain activity at the implant site, unperceived by the patient. The device is programmed by physicians to detect electrical patterns that can lead to seizures., which are different for every individual. The system is designed to detect brain patterns which lead to seizures, then disrupt those patterns, preventing seizures. The system also provides information to a patient's doctor about seizure frequency and electrocoricographic activity. The RNS System is surgically implanted in the skull by a trained neurosurgeon and typically involves an overnight stay in the hospital. The therapy is reversible; the procedure does not involve removing any brain tissue.
Research
The RNS System was evaluated in a multi-center, prospective, randomized, controlled, double-blinded clinical study. The study included adults who have medically refractory, partial onset seizures with up to two localized seizure foci, and who had failed at least two medications. In total, 191 patients were randomized 1:1 to either treatment with the RNS System or sham stimulation. After the four month blinded period, stimulation was turned on for all patients. Treatment with the RNS System resulted in statistically significant seizure reductions compared to the sham group. By the end of the blinded period, patients in the Treatment group had a 41.5% reduction in disabling seizures compared to 9.4% in the Sham group. The safety profile of the RNS System compared favorably to deep brain stimulation as well as implantation of intracranial electrodes and epilepsy surgery. Patients treated with the RNS System experienced seizure reductions in the first year that continued to improve over time. At seven years, patients achieved a 72% median reduction in seizures. Patients treated with the RNS System reported statistically significant improvements in mood and overall quality of life, including physical health, mental health, cognitive effects, and seizure worry. Patients treated with the RNS System showed statistically significant improvements in naming and verbal memory. This is meaningful because individuals with epilepsy are at risk for cognitive disability and decline which has also been associated with other epilepsy treatments. For example, many antiepileptic drugs have adverse cognitive effects, patients treated with deep brain stimulation have reported cognitive decline, and epilepsy surgery carries risks for decline in cognitive areas specifically related to those regions of the brain that are resected. The therapy is claimed to be less invasive than other therapies such as vagus nerve stimulation, which can have chronic stimulation-related side effects such as voice alterations, coughing, throat discomfort, and shortness of breath.
