The RNS® System LTT study is designed to assess the ongoing safety and to evaluate the long-term efficacy of the RNS® System as an adjunctive therapy in reducing the frequency of seizures in individuals 18 years of age or older with partial onset seizures that are refractory to two or more antiepileptic medications. Candidates will continue to receive their epilepsy medications while participating in the trial.

NeuroPace, Inc. is sponsoring an investigational device study of the RNS® System, the first closed loop responsive brain stimulator designed to treat refractory epilepsy. The RNS® System LTT study is an open-label multi-center prospective 7-year clinical investigation which follows completion of the RNS® System Pivotal or Feasibility study. Data regarding safety and efficacy are collected at 6-month intervals, and data regarding quality of life are collected at yearly intervals.

The study is designed to assess the ongoing safety and to evaluate the long-term efficacy of the RNS® System as an adjunctive therapy in reducing the frequency of medically uncontrolled and disabling partial onset seizures that start from one or two areas of the brain.

The RNS® System LTT study will provide additional data on the safety and efficacy of the RNS® System for 7 years following a subject's completion of the RNS® System Feasibility or Pivotal studies. Data from the RNS® System LTT study will be combined with data collected during the RNS® System Feasibility and Pivotal studies, resulting in 9 total years of post-implant follow-up data. These data will be used to calculate long-term SAE rate, percent change in seizure frequency (from pre-implant baseline), as well as the frequency of sudden unexplained death in epilepsy (SUDEP).

The RNS® Neurostimulator (a pacemaker-like device) and NeuroPace® Leads (tiny wires with electrodes) are implanted in the head. The Neurostimulator is a battery powered, microprocessor controlled device that detects and stores records of electrographic patterns (such as epileptiform, or seizure-like, activity) from the Leads within the brain. When the device detects an electrographic pattern, it responds by sending electrical stimulation through the Leads to a small part of the patient's brain to interrupt the electrographic pattern. This type of treatment is called responsive stimulation, but it is not yet known if it will work for the treatment of epilepsy. Direct brain stimulation therapy has already received approval in the United States, Europe, Canada, and Australia for the treatment of Essential Tremor and Parkinson's disease. Direct brain stimulation is not approved for the treatment of epilepsy.

Inclusion Criteria:

1. Subject has completed either the RNS® System Pivotal or Feasibility study
2. Subject has an implanted RNS® System
3. Subject has elected to continue to receive responsive neurostimulation therapy after completion of the RNS® System Pivotal or Feasibility study
4. Subject is able to attend scheduled appointments for the RNS® System LTT study

Exclusion Criteria:

1. Subject has active psychiatric or medical illness that makes it inadvisable for the subject to continue to receive responsive neurostimulation therapy with the RNS® System
2. Subject has been diagnosed with psychogenic or non-epileptic seizures, or primarily generalized seizures during the RNS® System Pivotal or Feasibility study
3. Subject has been noncompliant with scheduled appointments during the RNS® System Pivotal or Feasibility study
4. Subject has been noncompliant with maintaining seizure diaries during the RNS® System Pivotal or Feasibility study
5. Informed consent cannot be obtained from subject or caregiver