Long-term outcomes and prognosis factors of vagus nerve stimulation in patients with refractory epilepsy

Abstract

Background Vagus nerve stimulation (VNS) is an effective treatment for patients with refractory epilepsy, yet with varied predictive factors and heterogeneous long-term outcomes. Adjustment of VNS parameters is critical for obtaining favorable efficacy. In this study, we aimed to investigate the long-term outcomes and the possible predictive factors of VNS in patients with refractory epilepsy. Methods Eighty-six patients (59 males and 27 females) who underwent VNS implantation for treatment of refractory epilepsy between May 2016 and May 2017 at five Epilepsy Centers were enrolled. The clinical data, including sex, age at epilepsy onset, VNS implantation, epilepsy duration, seizure type, MRI findings, history of neurosurgical operations, and responder rate (responders were those with ≥50% seizure reduction), were analyzed. Results Four-year follow-up data were available for 76 patients (53 males and 23 females). The mean current intensity at the last follow-up was 1.8 ± 0.3 mA (range: 0.75–2.5 mA). The mean seizure reduction was 36.2% at 6 months, 38.5% at 1 year, 69.4% at 3 years, and 56.7% at 4 years. A favorable outcome of ≥50% reduction in seizure frequency occurred in 40.0% of the patients at 6 months, 55.9% at 1 year with 4 patients being seizure-free, 63.2% at 3 years with 5 patients being seizure-free, and 68.4% at 4 years with 5 patients being seizure-free. Earlier onset age (P < 0.001) and shorter duration (P = 0.042) were associated with favorable prognosis. Compared with generalized tonic-clonic seizures, tonic seizures had a favorable outcome (P = 0.026). Twenty-three patients underwent neurosurgical operations before VNS implantation, and the responder rate was 60.9% at the last follow-up. Conclusions VNS is an adjunctive and effective treatment for patients with refractory epilepsy who are not good candidates for surgical resection or have failed to respond to surgical treatment. The stimulation efficacy increases over time after implantation, and earlier exposure to VNS improves the prognosis.

Vagus Nerve Stimulation for Drug Resistant Epilepsy: Clinical Outcome, Adverse Events, and Potential Prognostic Factors in a Single Center Experience

“…However, in a meta-analysis that recruited 5554 patients from the VNS therapy Patient Outcome Registry and 78 clinical studies, the authors found that patients with age of epilepsy onset >12 years were more likely to be seizure-free than the younger patients, by multivariate analysis (OR, 1.89; 95% CI, 1.01-1.85) [20]. Xu et al using a generalized linear mixed-effect model, found that earlier onset age (OR, 1.11; 95% CI, 1.06-1.16) and shorter duration of epilepsy (OR, 1.04; 95% CI, 1.00-1.07) presented a favorable clinical outcome [21].…”

Locus coeruleus features are linked to vagus nerve stimulation response in drug-resistant epilepsy

“…In this pilot study, two models were used to assess independently the relationship between the LC features and VNS response or therapy duration, to avoid possible multicollinearity issues. Indeed, it has been reported that response rate to VNS increases with therapy duration ( Xu et al, 2022 ). In addition, while no difference in therapy duration was found between R/PR and NR in the present pilot study, the statistical approach considering independently VNS response and therapy duration in the models may be useful in studies with larger cohort of patients, where these two variables may not be independent.…”

Characterization of Vagus Nerve Stimulation (VNS) Dose-Dependent Effects on EEG Power Spectrum and Synchronization

“…Recent findings show an encouraging increase in the responder rate, with the most significant seizure frequency reduction observed within the first one to two years after starting therapy [ 3 , 4 ]. The efficacy of VNS stimulation increases with time after implantation, and earlier exposure to VNS improves prognosis [ 5 ], which may result from VNS-induced neuroplastic changes [ 6 ].…”