Objective:

To determine if earlier referral for vagal nerve stimulator implantation improves outcomes in drug resistant epilepsy. 

Background:

Current literature demonstrates that decreased time from epilepsy onset to
epilepsy surgery in drug-resistant epilepsy (DRE) patients leads to greater efficacy
rates. It is unclear if this is true for vagal nerve stimulation.

Design/Methods:

This is a retrospective cohort of patients of all ages who received Vagal Nerve
Stimulators (VNS) for DRE at Walter Reed National Military Medical Center from
January 2000 – December 2023. Variables including age at seizure onset, age at VNS
implantation, year of VNS implantation, race, sex, seizure type, epilepsy surgery prior to
VNS, maximum duty cycle of their VNS parameters. Response to VNS therapy was defined by a 50% reduction in seizure frequency. Outcomes were collected after review of the electronic health record.

Results:

We identified 55 patients (45% female), with a majority having focal-onset
seizures (66%). The median age of onset was 4 years old, with a range of 0-43 years of
age. Median time to VNS placement was not significantly lower for responders than for
non-responders (7.0 years vs. 10.5 years, p = 0.33). Patients who had VNS implanted
within five years of seizure onset represented 25% of our patient population and had a
significantly higher proportion of responders compared to the rest of the population
(O.R. 3.9, p = 0.028). Male patients had significantly better outcomes than females
(O.R. 3.1, p = 0.048). Median age at seizure onset was not significantly different
between responders and non-responders (3.0 years vs. 5.0 years, p = 0.16). We found
that patients with infantile-onset epilepsy were exceptions to an otherwise inverse relationship between age at seizure onset and response to VNS.

Conclusions:

VNS placement within five years of epilepsy onset had a higher rate of
obtaining 50% reduction in seizure frequency.