Outcome and predictors of response to vagus nerve stimulation for drug-resistant epilepsy: a retrospective cohort study

Vagus nerve stimulation (VNS) has been used as an adjunctive therapy for patients with drug-resistant epilepsy (DRE) for decades. Nonetheless, the predictors of response to VNS remain inadequately characterized. We aimed to find factors associated with responder status. We retrospectively reviewed records of patients who received VNS for DRE in our medical center between 2000 and 2023. Preoperative data and VNS parameters were analyzed with univariate and multivariate analysis to identify predictors associated with responder status. We used receiver operating characteristic (ROC) curves to select possible related factors and the cutoff values. The overall responder rate was 35.8%. Individuals with generalized epilepsy demonstrated significantly higher responder rates (86%) compared to those with focal (29%) or combined epilepsy (28%). Univariate analysis indicated that an epilepsy duration of < 5 years at the time of VNS implantation (p = 0.021) and a diagnosis of generalized epilepsy (p = 0.016) were associated with a favorable response. A multivariate logistic regression analysis confirmed these findings. There was no correlation between age at implantation, prior epilepsy surgery, VNS parameters, such as output current and duty cycle, and the responder status. An epilepsy duration of < 5 years at VNS implantation and generalized epilepsy are independent predictors of responder status to VNS. Future long-term, randomized controlled trials with larger cohorts are needed to better evaluate these critical variables and their association with VNS outcomes.