Authors :
Shaan Braich, BS – Kern Medical
Clins Chacko, BS – Kern Medical
Presenting Author: Wefaq Alshami, BS – Kern Medical
Charles Liu, MD, PhD – University of Southern California
Hari Prasad Kunhi Veedu, MD – Kern Medical
Rationale:
Vagus nerve stimulation (VNS) is an FDA approved palliative neuromodulation therapy for refractory focal epilepsy patients who are ineligible for surgery. This retrospective study evaluates seizure burden outcomes following VNS implantation in the underserved population of Kern County to assess VNS efficacy.Methods:
A cohort of 74 patients who underwent VNS implantation from 2016-2024 were identified. Data was collected via patient charts and telephonic interviews. Baseline seizure burden was an average self-reported count from the patient/family, a minimum 3 months pre-VNS. Seizure classification was categorized by video electroencephalogram monitoring prior to VNS implantation. Seizure frequency of first implantation patients was recorded after 6 months and seizure frequency of patients who underwent VNS battery replacement was recorded after 5 years post initial implant. For this study, change in seizure burden was categorized with a modified McHugh Scale: Class I (seizure freedom), Class II (80-99% reduction), Class III (50-79% reduction), Class IV (< 50% reduction), and Class V (no improvement). Class I was defined as no seizure for 12 months or at least 3 times the duration of their longest pre-intervention interseizure interval in the prior 12 months, whichever was longer.Results:
In the cohort, 52.7% were male and 47.3% were female, with a mean age 43.4 years. Overall, 36.5% underwent first implantation while 63.5% underwent battery replacement surgeries. Prior to VNS implantation, the average number of anti-seizure medications tried was 6, with the average time from age of onset to implantation being 24.2 years. All together, 13.5% of patients had Class I seizure reduction, while 20.3% of patients had Class V outcomes after a minimum 6 months post implantation. Of the patients classified as responders (≥ 50% reduction in seizure frequency), n=52, 28.8% were first implantation patients, while 71.2% were battery replacement patients. 4 patients reported complications with VNS surgery, of which 2 had the device explanted.Conclusions:
In conclusion, the efficacy of VNS is comparable to more invasive neuromodulation therapies like Deep Brain Stimulation (response rate [RR] of 53.2%, 5 years post implantation) and Responsive Neurostimulation (RR of 84%, 3 years post implantation) [1,2]. In Class V patients, although VNS implantation didn’t affect frequency, severity of seizures were reduced. However, the nearly 25-year wait between epilepsy onset and implantation of VNS devices highlights the staggering sluggishness of epilepsy care, even for the most widely used device, and the continued need for epilepsy care expansion.
References
[1]Peltola J, et al. Deep Brain Stimulation of the Anterior Nucleus of the Thalamus in Drug-Resistant Epilepsy in the MORE Multicenter Patient Registry. Neurology. 2023;100(18):e1852-e1865. doi:10.1212/WNL.0000000000206887
[2]Razavi B, et al. Real-world experience with direct brain-responsive neurostimulation for focal onset seizures. Epilepsia. 2020;61(8):1749-1757. doi:10.1111/epi.16593
Funding: None