Abstracts

Rationale: About one-third of epilepsy patients develop drug-resistant epilepsy, for which surgery is an effective treatment option. For some patients however, resective surgery is not an option due to multifocal ictal zones, ictal onset within eloquent cortex, poorly localized ictal onset, or patient preferences. Neuromodulation techniques, such as responsive neurostimulation (RNS), offer an alternative approach for these patients, who otherwise have very limited options for improving their seizure control. This study assesses outcomes of patients treated with RNS at our epilepsy center.

Methods: We created a database of adult patients who underwent RNS implantation and/or received RNS management at our level 4 comprehensive epilepsy center. Data includes demographics, epilepsy diagnosis features, presurgical evaluation, electrode implantation parameters, seizure outcomes, and quality of life (QOL). All outcomes reported were derived from the patient’s most recent encounter.

Results: In total, 40 patients were implanted with RNS. Of these patients, 53% were women and 45% men; 93% were white, 5% Black, and 3% Asian. Median age at implantation was 33 years (interquartile range [IQR] 27-40). Common etiologies included mesial temporal sclerosis (15%), focal cortical dysplasia (15%), periventricular nodular heterotopia (10%), and CNS infection (8%). MRI lesions were observed for 77% of patients. Intracranial EEG was performed prior to RNS implantation for 90% of patients. Of the 35 patients who underwent intracranial EEG prior, 23/35 patients were found to have multifocal ictal onsets. Six patients had previously undergone resective surgery; 14 patients had current or prior vagal nerve stimulation (VNS). The most common seizure types were focal-to-bilateral tonic-clonic (70%) and focal motor with impaired awareness (55%). Electrodes were implanted in the mesial temporal region (25 patients), neocortical temporal region (8), frontal lobe (5), parietal lobe (5), occipital lobe (3), and insular region (5). There were no peri-operative complications of RNS implantation: one patient had infection 6 weeks later and one patient had delayed skin erosion. Median length of follow up after implantation was 55 months (IQR 29-70). Of patients who had focal-to-bilateral tonic-clonic seizures prior to RNS implantation, 29% no longer had this seizure type after. Of patients who had focal motor seizures with impaired awareness prior to RNS implantation, 9% no longer had this seizure type after. For 39 patients Engel outcomes were available: 15/39 had an Engel Class (EC) 1 outcome, 3/39 EC II, 14/39 EC III, and 7/39 EC IV. A >50% decrease in disabling seizures was achieved by 22/38 patients. For 38 patients QOL was available: QOL was “much better” for 13/38 patients, “better” for 11/38, “no change” for 13/38, and “much worse” for 1/38. Results were limited for some patients due to loss to follow up and short interval since implantation.

Conclusions: Our study highlights the effectiveness of RNS in patients with severe epilepsy. A considerable proportion (46%) achieved seizure-freedom or near seizure-freedom (EC I and II). The majority (63%) experienced improved QOL.

Funding: None.