837 Responsive Neurostimulation of the Thalamus for the Treatment of Refractory Epilepsy

Abstract

INTRODUCTION: One-third of patients with epilepsy experience seizures despite antiepileptic medications. Some of these refractory patients may not be candidates for surgical resection. The Responsive Neurostimulation System (RNS) is a closed-loop device that uses programmable detection and stimulation. METHODS: We performed a prospective single-center study of consecutive refractory epilepsy patients who underwent RNS system implantation in the anterior (ANT) and centromedian (CM) thalamic nuclei from September 2015 to December 2020. Patients were followed postoperatively to evaluate seizure freedom and complications. RESULTS: Twenty-three patients underwent placement of 36 RNS thalamic leads (CM = 27 leads, ANT = 9 leads). Mean age at implant was 18.8 ± 11.2 years. Two patients (8.7%) developed infections: 1 improved with antibiotic treatments alone, and 1 required removal with eventual replacement of the system. Mean follow-up was 22.3 months. Based on overall reduction of seizure frequency, 2 patients (8.7%) had no- to <25% improvement, 6 patients (26.1%) had 25-49% improvement, 14 patients (60.9%) had 50-99% improvement, and 1 patient (4.3%) became seizure-free. All patients reported significant improvement in seizure duration and severity, and 17 patients (74%) reported improved post-ictal state. There was a trend for subjects with foci located in the temporal lobe to achieve better outcomes after thalamic RNS compared to those with extratemporal foci. Seizure etiology was syndromic in 12 cases (52.2%). CONCLUSIONS: Thalamic RNS achieved ≥50% seizure control in ∼65% of patients. Infections were the most common complication. This therapeutic modality may be particularly useful for patients affected by aggressive epilepsy syndromes since a young age, those whose seizure foci are located in the mesial temporal lobe, and those who have failed prior surgical interventions.