RNS System LGS Feasibility Study

To generate preliminary safety and effectiveness data for brain-responsive neurostimulation of thalamocortical networks as an adjunctive therapy in reducing the frequency of generalized seizures in individuals 12 years of age or older with Lennox Gastaut Syndrome (LGS) who are refractory to antiseizure medications. The intent is to determine the feasibility and the optimal design of a subsequent pivotal study in order to expand the indication for use for the RNS System as a treatment for patients with medically intractable LGS.

This study is a prospective two-stage single-blind feasibility cross-over study designed to provide early safety and preliminary evidence of effectiveness for combined bilateral brain-responsive neurostimulation of thalamocortical networks for the treatment of generalized seizures in patients with LGS. Twenty participants will be treated with the RNS System across six Comprehensive Epilepsy Centers in the U.S. Enrollment will be staged in two cohorts of 10. Once all 10 participants of the first cohort complete Treatment Block 1 and the interim analysis criteria are met, the next cohort of 10 participants will be enrolled. The research study comprises six study periods: 1. Baseline Period 2. Implant (surgery) 3. Post-Op Period 4. Blinded Evaluation Period (which is made up of 3 treatment blocks, one of which is a sham stimulation) 5. Open Label Period 6. Long Term Follow-Up Period Two neurostimulators will be placed: one in the parieto-temporal skull on the left, and the second in the homologous region on the right. Depth leads will target the bilateral CM. Cortical strip or depth leads will target the prefrontal cortex. Each neurostimulator will be connected to two ipsilateral leads: one in the prefrontal cortex and one in the CM. A total of two neurostimulators and four leads will be implanted. During the Blinded Evaluation Period, the participant will move through 3 different treatment blocks (Treatment Block1, Treatment Block 2, and Treatment Block 3) in a random order. Two of the blocks will have active stimulation treatment and one of the blocks will have no (sham) stimulation treatment. The participant and caregiver will be blinded to the treatment condition. * Condition A - active treatment of high frequency short burst stimulation * Condition B - active treatment of low frequency long burst stimulation * Sham - no stimulation treatment After completing the Blinded Evaluation Period the participant will transition to the 1-year Open Label Period and have study appointments every 3 months. After completing the 1-year Open Label Period the participant will transition to the Long Term Follow-up Period. The Long-Term Follow-up Period may last up to 2 years with appointments every 3 months until the participant complete this research or this research study ends.