Seizure Improvement with Low vs. High Output Current VNS Stimulation Among
Patients with Focal and Generalized Epilepsy.
Abstract number :
3.23
Submission category :
3. Neurophysiology / 3E. Brain Stimulation
Year :
2025
Submission ID :
1014
Source :
www.aesnet.org
Presentation date :
12/8/2025 12:00:00 AM
Published date :
Authors :
Presenting Author: Ryan Chung, BS – University of Arizona-Tucson
Shan Rizvi, BS – University of Arizona-Phoenix
Steve Chung, MD – University of Arizona, Banner–University Medical Center
Rationale: Since its FDA approval in 1997 for adults and adolescents over 12 with drug-resistant focal seizures, Vagus Nerve Stimulation (VNS) therapy has been widely utilized for various types of seizures. However, despite VNS therapy’s noted beneficial history and evidence for seizure improvement, proper patient selection and official stimulation parameter optimization remain ill-defined. Previous analysis of key stimulation parameters (output current, pulse width, signal frequency, and duty cycle) suggested that rapid duty cycling could be more effective in lowering seizure frequency. Herein, we evaluate the responses to lower stimulation output current for focal and generalized seizure.
Methods: We collected information on patients who previously underwent VNS implantation with at least one year of VNS therapy. Data regarding age of seizure onset, sex, seizure type, previous medical or surgical treatment, imaging findings, VNS stimulation parameters, seizure frequency, and seizure outcomes were collected. The main analysis of the study focused on seizure reduction relative to output current strength and seizure type. Subjects were divided into two groups, low output current (≤1.5 mA) vs. high output current ( >1.5 mA). Seizure outcomes were measured by responder rates.
Results: 146 patients (85 focal and 61 generalized epilepsy) were included in the study. Generalized epilepsy patients were further divided into idiopathic (IGE) or symptomatic epilepsies (including LGS). The overall ≥50% responder rate was 57% without significant differences between seizure types (52% in focal and 63% in generalized). Of these patients, 40% of women and 30% of men received low stimulation. In the low stimulation group (n=51), the overall responder rate was 54%, with the highest response in patients with IGE (58%), compared to 23% (p=0.049) and 16% (p=0.017) in patients with temporal lobe seizures and LGS respectively. No significant differences were noted with other VNS stimulation parameters such as duty cycle, signal frequency, or number of concurrent ASMs.
Conclusions: In VNS therapy, low output current strength can be effective for both focal and generalized seizures. Notably, IGE patients responded well to low strength stimulation relative to focal epilepsy and LGS patients. In our study no seizure outcome difference was noted with other VNS stimulation perimeters.
Funding: n/a
Neurophysiology