The FDA has approved the RNS System, a medical device by Neuropace, Inc., to help reduce the frequency of seizures in patients with epilepsy who have not responded well to medications. Specifically, it is indicated for use as an adjunct therapy in patients >18 years of age with partial onset seizures who have undergone diagnostic testing that localized no more than two epileptogenic foci, are refractory to >2 antiepileptic medications, and currently have frequent and disabling seizures (eg, motor partial seizures, complex partial seizures and/or secondarily generalized seizures).

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The RNS System consists of a small neurostimulator that is implanted within the skull. This neurostimulator is connected to one or two electrodes that are placed at the source of the seizures. It normalizes the  abnormal electrical activity in the brain through electrical stimulation before the patient experiences seizure symptoms. Physicians can program the detection and stimulation parameters of the implant non-invasively to individualize each therapy.

The approval is based on a 3-month randomized control trial in patients with drug-resistant epilepsy (n=191). By 3 months after implant activation, patients experienced a ~38% reduction in the average number of seizures per month, as compared to ~17% reduction in those who had the implant turned off (P=0.012).

By the end of 3 months, the median reduction in seizures was 34% with active use, and about 19% with inactive use. A total of 29% of patients experienced at least a 50% reduction in the overall number of seizures, as compared to 27% for those with the implanted device turned off. A 2-year follow-up phase also showed a continued reduction in seizure frequency.

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