Older Age of Onset Predicts Response to Vagal Nerve Stimulator Implantation in Patients With Medically Refractory Epilepsy

• Published in: Neurosurgery Vol. 67; no. Supplement_1
• Main Authors: Riestenberg, Robert, Sherman, Alain E, Clark, Austin J.S, Zwienenberg, Marike, Shahlaie, Kiarash, Alden, Tord D, Bandt, S. Kathleen
• Format: Journal Article
• Language: English
• Published: Philadelphia Wolters Kluwer Health, Inc 01.12.2020
• Subjects: Age; Convulsions & seizures; Deep brain stimulation; Epilepsy; Neurosurgery; Older people; Surgical techniques; Transplants & implants
• ISSN: 0148-396X; 1524-4040
• DOI: 10.1093/neuros/nyaa447_632

INTRODUCTION Vagus nerve stimulation (VNS) results in a clinically meaningful response in a subset of patients with medically refractory epilepsy. Predictors of positive treatment response remain poorly defined. METHODS We present a retrospective analysis of patients with medically refractory epilepsy who underwent VNS implantation at two institutions. Age of epilepsy onset, epilepsy risk factors (e.g., family history, traumatic brain injury, encephalitis), EEG and MRI reports, pre-VNS seizure frequency, and seizure frequency at last follow-up were extracted from the electronic record. Patients were categorized as seizure-free (cutoff ≥6 months), ≥50% seizure frequency reduction, or clinically insignificant effect. Time elapsed from VNS implantation to treatment effect was recorded. Univariate predictors of ≥50% seizure frequency reduction and seizure freedom were determined using Cox proportional hazards analysis. Univariate predictors with p < 0.05 were included in multivariate Cox regression models. RESULTS Eighty-seven patients were included in the study. Fifty-three (60.9%) patients achieved ≥50% seizure frequency reduction and 17 (19.5%) patients became seizure-free. Right-sided seizure onset (left vs. right HR = 0.376, P = .021; bilateral vs. right HR = 0.497, P = .047), history of stroke (HR = 2.679, P = .039), and age of epilepsy onset ≥15 years (HR = 2.122, P = .008) were significant univariate predictors of ≥50% seizure frequency reduction. Left hand dominance (HR = 3.811, P = .025), age of epilepsy onset ≥15 years (HR = 3.145, P = .029), and pre-VNS seizure frequency <5 per month (HR = 3.887, P = .011) were significant univariate predictors of seizure freedom. Age of epilepsy onset ≥15 years was the only significant multivariate predictor of ≥50% seizure frequency reduction (HR = 1.962, P = .02). Left hand dominance (HR = 5.637, P = .006) and pre-VNS seizure frequency <5 per month (HR = 3.789, P = .021) were predictive of seizure freedom in multivariate analysis. CONCLUSION Age of epilepsy onset of 15 years or later predicts significant reduction in seizure frequency following VNS, and left-hand dominance and pre-VNS seizure frequency <5 per month predict seizure freedom. These findings may be used to identify ideal candidates for VNS.