Efficacy of Vagus Nerve Stimulation in patients with drug-resistant epilepsy after resective surgical treatment

Abstract

Background. Vagus nerve stimulation (VNS) is used in patients with drug‑resistant epilepsy, including those who have previously undergone resective surgical interventions. Aim. To evaluate the efficacy and safety of VNS in patients with persistent epileptic seizures after resective surgery, to identify the favorable predictors of treatment response as well as to determine the optimal timing for VNS device implantation following previous surgical intervention. Materials and methods. The study included 40 patients in the main group who underwent resective epilepsy surgery followed by vagus nerve stimulator implantation, and 40 patients in the control group who received only resective surgery. Outcomes were assessed using the modified J. Engel Epilepsy Surgery Outcome Scale and the McHugh Outcome Scale. Results. The analysis of VNS efficacy outcomes in the main group (n = 40) using the modified J. Engel scale in 12 months after implantation showed, that Engel class I outcomes were observed in 12.5 % of patients, Engel class II ‑ in 12.5 %, Engel class III – in 55 %, and Engel class IV – in 20 %. In 24 months after VNS implantation, Engel class I outcomes were noted in 22.5 % of patients, Engel class II – in 10 %, Engel class III – in 57.5 %, and Engel class IV – in 10 %. At 36 months of follow‑up, Engel class I outcomes were observed in – 20 % of patients, Engel class II – in 27.5 %, Engel class III – in 47.5 %, and Engel class IV – in 5 % of patients. According to the McHugh Outcome Scale, in 12 months after VNS therapy, class I outcomes were achieved in 25 % of patients, class II – in 55 %, class III – in 12.5 %, class IV – in 5 %, and class V – in 2.5 %. In 24 months after VNS implantation, class I outcomes were observed in 32.5 % of patients, class II – in 57.5 %, class III – in 5 %, class IV – in 2.5 %, and class V – in 2.5 %. At 36 months of follow‑up, class I outcomes were achieved in 47.5 % of patients, class II – in 47.5 %, class III – in 2.5 %, class IV – in 3.5 %, while no class V outcomes were observed. The most frequently reported stimulation‑related adverse events included cough (30 %), hoarseness (22.5 %), throat discomfort (12.5 %), and discomfort in the face, neck, and chest regions (5 %). Conclusion. In patients with drug‑resistant epilepsy who previously underwent resective surgery, VNS resulted in more or equal 50 % reduction in seizure frequency in 80% of patients during the first 12 months of follow‑up. With continuous stimulation, the effectiveness of the therapy increased over time. The most favorable time for VNS implantation and initiation of stimulation is within the first 16.5 months following resective epilepsy surgery.