Abstracts

This is a Late Breaking abstract

Rationale: Age is a known independent risk factor for epilepsy. The prevalence of epilepsy in the elderly has been shown to be approximately 2% to 5%, which is three to four times higher than in younger adults. With over 125,000 patients treated worldwide, vagus nerve stimulation (VNS) is an established adjunctive therapy for drug resistant epilepsy (DRE). In the randomized-controlled trials conducted for approval of the VNS Therapy System in the early 1990s, the average participant was in their early 30s with a mean duration of epilepsy of approximately 20 years at the time of VNS implantation. Recently many clinical investigations of VNS have focused on its application in pediatric DRE; however, limited data are available on use of VNS Therapy in the elderly population and in late onset epilepsy.

Methods: A pooled database of all prior VNS studies sponsored by LivaNova was queried to identify subjects based on age at implant and duration of epilepsy at implant. The studies included randomized controlled trials as well as open-label observational studies, and not all studies recorded seizure outcomes at the same timepoints. Only patients receiving VNS Therapy were considered. Seizure rates at baseline were compared to recorded seizure rates at post-implant follow-ups at 3, 6, and 12 months. No data were imputed for missing visits or dropouts. Changes in anti-seizure medication were allowed in some of the studies included in this pooled analysis.

Results: A total of 247 patients with an age of 40 or older at the time of VNS implantation were identified from the pooled database of 1,191 patients (21%) (E03, E05, E06, E40, E100, and E104). At 12 months of VNS Therapy (n=149), 50.3% of patients were responders (defined as a 50% or greater reduction of seizure frequency compared to baseline), and the median reduction of seizure frequency was 50%. When looking at age-at-implant-based subgroups, we found that at 12 months responder rates were similar in the groups 40-49 (n=84) and 50-59 (n=45): 48.8% vs. 48.9% respectively. A slightly higher responder rate was found in the group of patients aged 60 and older at implantation (n=20): 60% of these patients were responders, and the median seizure frequency reduction was 56.6% at 12 months. The greatest response was observed in the late onset epilepsy group (aged 40 or older at epilepsy-onset; n=26, 2.2%)): at 12 months (n=16), 68.8% of patients were responders, 31.3% of patients experienced more than 80% seizure frequency reduction, and the median seizure frequency reduction is 66.8%. 

Conclusions: Our analysis suggests that efficacy of VNS in patients over the age of 40 is at least similar to younger adult patients investigated in prior VNS studies. Whether patients with a greater age at implantation or later onset of epilepsy may have better outcomes or have a different long-term neuromodulatory effect warrants further investigation in larger, more homogenous data sets.

Funding: Maxine Dibué, Ryan Verner, and Charles Gordon participated in datapooling, stastical analysis, and abstract wording. All are employees of LivaNova PLC.