Abstracts

Rationale: Vagus nerve stimulation (VNS) is FDA approved as adjunctive therapy for patients with medically refractory focal onset seizures who are not candidates for resective or ablative surgery. While numerous studies demonstrate that VNS is also effective for patients with generalized epilepsy, there are very few that evaluate whether timing from onset to VNS surgery affects outcomes in these patients.

Methods: All patients 12-65 years of age with generalized epilepsy refractory to at least 2 medications who underwent placement of a VNS device at Tampa General Hospital between 2018 to 2021, and who had at least a one-year follow-up were identified through retrospective chart review and were contacted via phone interview. Primary endpoints include seizure outcome expressed as ≥ or < 50% seizure reduction and reduction in the severity of most disabling seizures. Seizure outcomes were compared by years between onset of generalized epilepsy and implantation of VNS. Secondary endpoints include the percentage improvement in discrete seizure subtypes, rates of peri-operative complications and device-related adverse events, and mortality including the incidence of Sudden Unexpected Death in Epilepsy (SUDEP).

Results: To date, 17 patients have been identified with the average length of follow-up being approximately 2 (0.9-3.6) years. 59% of patients reported ≥ 50% seizure reduction of which one became seizure free. Of patients with < 50% seizure reduction, 35% and 6% reported no change and increased seizure frequency, respectively. Additionally, 53% of patients reported a reduction in the severity of their most disabling seizures, while 29% and 12% of patients reported no change and increased seizure morbidity respectively. Patients reporting a reduction in generalized tonic-clonic and atonic seizures manifested a 50% reduction in frequency for these seizure subtypes on average. No perioperative complications or documented cases of SUDEP were identified, and 36% of patients describe bothersome but transient hoarseness, voice change, and coughing when the device goes off. Only 1 patient could not tolerate the VNS at effective settings due to coughing leading to re-titration of his therapy. Two patients received VNS within 10 years of diagnosis, 9 patients within 20 years, 4 patients within 30 years, 1 patient within 40 years, and 1 patient within 50 years. A regression analysis of our preliminary data shows no statistically significant association between seizure outcomes and time from diagnosis to implantation (OR, 95%CI 1.02, 0.93-1.12; p=0.674). However, data collection and analysis are ongoing.

Conclusions: If earlier VNS treatment improves refractory epilepsy, this association may impel changes in the work-up and management of these patients, including a prospective trial of VNS in this patient population potentially leading to FDA approval for these indications.  

Funding: None