The Efficacy and Safety of Rapid Cycling Vagus Nerve Stimulation in Children With Intractable Epilepsy

Vagus nerve stimulation (VNS) is an effective adjunctive therapy for drug-resistant epilepsy. Nevertheless, information is lacking regarding optimization of stimulation parameters to improve efficacy. Our study examines the safety and efficacy of rapid duty cycle VNS (OFF time ≤1.1 minute keeping duty cycle less than 50%) in pediatric cohort with intractable epilepsy.

Retrospective chart review of 50 patients (one to 17 years) with drug-resistant epilepsy treated with VNS between 2010 and 2015 at a single pediatric epilepsy center. Safety and tolerability data were aggregated across all patient visits to determine frequency of adverse events between differing duty cycles. We also compared seizure reduction rates for each patient at (1) last regular duty cycle visit, (2) first rapid duty cycle visit, and (3) last recorded rapid duty cycle visit.

Rapid duty cycle was well tolerated, with no adverse events reported in 96.6% patient encounters. At the last visit before switching to rapid duty cycle 45.5% patients were showing response to VNS (seizure reduction rates ≥50%). This rate increased to 77.3% after switching to rapid duty cycle and remained at 77.4% at the last rapid duty cycle visit. Fifteen patients (34.1%) became responders to VNS after switching to rapid cycling; another 19 (43.2%) maintained their response with mostly improved seizure reduction rates. In only a few instances, responders became nonresponders after switching to rapid duty cycle.

Rapid duty cycle VNS is probably safe and well tolerated; it may also be more efficacious than regular cycling VNS in some patients. This study highlights the necessity of prospective, long-term, double-blinded studies for understanding the advantages of this VNS modality.