The RNS® System Pivotal study is designed to assess safety and demonstrate that the RNS® System is effective as an adjunctive (add-on) therapy in reducing the frequency of seizures in individuals 18 years of age or older with partial onset seizures from no more than two foci (two areas of the brain) that are refractory (drug-resistant or hard-to-treat) to two or more antiepileptic medications. Patients continue to receive their epilepsy medications while participating in the study.

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 Pivotal study is a multi-center, randomized, double-blinded, sham-stimulation controlled investigation being conducted at 32 epilepsy centers throughout the United States. The study is designed to assess safety and demonstrate that the RNS® System is effective in reducing the frequency of medically uncontrolled and disabling partial onset seizures that start from one or two areas of the brain.

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.

Subjects participating in the RNS® System Pivotal study must met inclusion criteria, including localization of epileptogenic region(s), prior to enrolling in the study. Throughout the entire study, subjects or their caregivers must keep a seizure diary. Seizure frequency, seizure severity, and antiepileptic medications, as well as physical and emotional health will be monitored and recorded throughout the study.

Upon demonstrating the required seizure frequency and stable antiepileptic medications over 3 consecutive months of the Baseline (pre-implant) Period, subjects will qualify for RNS® System implantation. Antiepileptic medications should continue to remain stable until 6 months post-implant. The surgical procedure will be performed within one month of qualification.

The RNS® Neurostimulator is cranially implanted and connected to one or two NeuroPace® Leads implanted in the brain. The investigational team will determine the placement of the Leads based on prior localization of the epileptogenic region, according to standard localization procedures. Detection of epileptiform activity will be enabled for all subjects during the 1 month Post-Operative Stabilization Period. Subjects will be randomized 1:1 to either the Treatment or Sham group prior to starting the 1 month Stimulation Optimization Period. During this period subjects are seen on a weekly basis by the Treatment Protocol investigator. Responsive stimulation will be enabled and optimized for subjects randomized to the Treatment group. Subjects randomized to the Sham group will be seen for simulated stimulation programming in order to maintain the treatment blind.

The Blinded Evaluation Period is comprised of months 3, 4, and 5 post-implant. Subjects in the Treatment group will receive responsive stimulation and subjects in the Sham group will not. Subjects will not know whether responsive stimulation is being delivered or not. At the end of the 5th month, all subjects' transition into the Open Label Evaluation Period during which all subjects may receive responsive stimulation and antiepileptic medications may be adjusted as medically required.

Subjects will be followed for 2 years post-implant. Throughout study participation, both effectiveness and safety data will be monitored continuously, and reviewed and documented by the study investigator at study appointments scheduled every month for the first year post-implant, then every 3 months.

Inclusion Criteria for enrollment:

1. Subject has disabling motor simple partial seizures, complex partial seizures, and/or secondarily generalized seizures. Disabling refers to seizures that are severe enough to cause injuries or significantly impair functional ability.
2. Subject's seizures are distinct, stereotypical events that can be reliably counted.
3. Subject failed treatment with a minimum of 2 anti-seizure medications.
4. Subject has remained on the same antiepileptic medication(s) over the 3 most recent consecutive months (other than acute, intermittent use of benzodiazepines). Subjects on the ketogenic diet are permitted if the diet has been stable for the preceding 3 months.
5. Subject reports having an average of 3 or more disabling motor simple partial seizures, complex partial seizures and/or secondarily generalized seizures per month over the 3 most recent consecutive months, with no month with less than 2 seizures.
6. Subject is between the ages of 18 and 70 years.
7. Subject has undergone diagnostic testing that has identified no more than 2 epileptogenic regions.
8. Subject is male or a female of childbearing potential using a reliable method of contraception or is at least two years post-menopause.
9. Subject or legal guardian is able to provide appropriate consent to participate.
10. Subject can be reasonably expected to maintain a seizure diary alone or with the assistance of a competent individual.
11. Subject is able to complete regular office and telephone appointments per the protocol requirements.
12. Subject is willing to be implanted with the RNS® System as a treatment for his/her seizures.
13. Subject is able to tolerate a neurosurgical procedure.
14. Subject is considered a good candidate to be implanted with the RNS® System.

Note: A subject is still eligible to participate if antiepileptic medication(s) were temporarily discontinued for the purposes of diagnostic or medical procedures during the preceding 3 months.

Exclusion Criteria for enrollment:

1. Subject has been diagnosed with psychogenic or non-epileptic seizures in the preceding year
2. Subject has been diagnosed with primarily generalized seizures.
3. Subject has experienced unprovoked status epilepticus in the preceding year.
4. Subject has a clinically significant or unstable medical condition (including alcohol and/or drug abuse) or a progressive central nervous system disease.
5. Subject is taking chronic anticoagulants.
6. Subject has been diagnosed with active psychosis, major depression or suicidal ideation in the preceding year. Subjects with post-ictal psychiatric symptoms need not be excluded.
7. Subject is pregnant or planning on becoming pregnant in the next 2 years.
8. Subject is enrolled in a therapeutic investigational drug or device trial.
9. Subject has an implanted Vagus Nerve Stimulator (VNS) or is unwilling to have the VNS explanted. (VNS therapy must have been discontinued for at least 3 months prior to enrollment.)
10. Subject has had therapeutic surgery to treat epilepsy in the preceding 6 months.
11. Subject has had a cranial neurosurgical procedure (including endovascular procedures) other than an epilepsy surgery involving the skull or brain in the previous month.
12. Subject is implanted with an electronic medical device that delivers electrical energy to the head.
13. Subject is an unsuitable candidate for neurosurgery.
14. Subject requires repeat MRIs in which the head is exposed to the radio frequency field.
15. Subject's epileptogenic region(s) is/are located caudal to the level of the thalamus.
16. Implantation of the RNS® Neurostimulator and Lead(s) would present unacceptable risk.