Vagus nerve stimulation for refractory epilepsy: a 24-year single-center experience

Approved in 1997, vagus nerve stimulation (VNS) is now a mainstay treatment of refractory epilepsy. While the safety and efficacy of this treatment modality are well established, the authors investigated the patient- and disease-related factors that impact efficacy.

The authors conducted a retrospective analysis of 356 patients who underwent VNS therapy at their center from 2000 to 2023. Data collected included age at implantation, age of first seizure, seizure type and etiology, seizure frequency and number of antiseizure medications before and after VNS, presurgical workup, and second surgery after VNS implantation. Responders were classified as those with at least 50% improvement in seizure frequency. Primary outcome was ≥ 50% reduction in seizure frequency.

Age at implantation and sex had no significant effect on seizure frequency. Patients with low seizure frequency had a significantly better response than patients with other seizure frequencies. Patients with a baseline seizure frequency of 1-2/year (OR -3.14, 95% CI -5.371 to -0.909) had significantly better outcomes than the other groups, and patients with baseline seizure frequency of 1-2/month also had a significant outcome (OR -1.803, 95% CI -2.875 to -0.730). The authors' study showed no significant difference in VNS outcomes based on known etiology and imaging findings. Patients with 1-2 seizures/year also had a significant decrease in antiseizure medication burden after surgery (p = 0.026).

This study showed that patients with refractory epilepsy who experience low baseline seizure frequency (< 1-2/month and < 1-2/year) received the most benefit from VNS. All patients with refractory seizures should be considered for VNS therapy but should undergo careful case selection to manage expectations and maximize seizure outcomes and medication burden.