Abstracts

Rationale: The RNS® System (NeuroPace, Inc.) is a brain-responsive neurostimulation system that is FDA-approved as an adjunctive treatment for adults with focal onset seizures. This study reports the first year patient outcomes from a 5-year prospective open-label post-approval study (PAS) in a 30 site cohort of patients. Methods: Adults with medically intractable focal onset seizures localized to 1 or 2 seizure foci were enrolled and treated with the RNS System. Efficacy assessments included median % change in seizure frequency and responder rate (RR, % of subjects with ≥ 50% seizure reduction). Safety was assessed by reporting of adverse events. Results: As of 04/01/2019, 191 adults were enrolled and treated. At enrollment, the mean age was 36.7 years, mean epilepsy duration was 16.9 years, and median baseline seizure frequency was 5.7 seizures/month (IQR: 2.7 to 16.7 seizures/month). Mean follow-up was 1.4 years (range: 0 - 3.8 years) with a cumulative 265 patient implant years. One hundred and twenty-eight patients had ≥ one year follow-up and were included in the efficacy analyses. As presented in Figure 1, the median % reduction was 68% (IQR: 16.1 to 96.0%) and the responder rate was 61% (95% CI: 52.3-69.0%) at the end of year 1. In addition, 34.4% of patients with at least a year of follow-up experienced one or more periods of ≥ 6-months without seizures, and 42.2% experienced ≥ 90% reduction in seizure frequency in their most recent 6 months of follow-up. There were no unanticipated device-related serious adverse events (SAEs). Four of the 191 patients had SAEs related to intracranial hemorrhage that were not attributed to seizure related head trauma. One patient experienced persistent mild right upper extremity weakness, one patient had transient headache and facial droop, one had transient confusion, seizures and left visual field deficit, and one was asymptomatic. Two patients at one center reported cerebrospinal fluid leakage at the site of the neurostimulator implant. The rate of infection was 2.0% per procedure (initial implant, replacement, explant or lead revision), and all infections were soft tissue only. Conclusions: Patients treated with the RNS System in the PAS experienced a median reduction in seizure frequency that reached 68% at 1 year. This is higher than the seizure reductions observed at a similar time point in the initial randomized controlled (Pivotal) trial of the RNS System, in which the 1 year seizure reduction was 44%. Experience gained in the Pivotal and long-term open label studies with clinical use of brain-responsive neurostimulation could explain these improved outcomes, especially since the demographic and seizure characteristics of PAS patients are similar. The safety experience in the PAS appears to be consistent with the experience reported in the initial studies. This early experience in a prospective post-approval study continues to support the safety and effectiveness of treatment of medically intractable focal seizures with the RNS System. Safety and efficacy will be further evaluated as the enrollment approaches the planned 300 patients and additional follow-up data are available. Funding: No funding