Long‐term outcome of epileptic dogs treated with implantable vagus nerve stimulators

Abstract

AbstractBackgroundThe long‐term effect of implantable vagus nerve stimulators (VNS) on seizures has not been evaluated in epileptic dogs.ObjectivesReport seizure frequency in medication‐resistant epileptic dogs before and after VNS implantation.AnimalsTwelve client‐owned dogs with idiopathic epilepsy and >1 seizure day per 3 weeks despite 3 months of appropriate use of 2 antiseizure medications and seizure diaries maintained 6 months before and >12 months after VNS implantation.MethodsUncontrolled, open‐label, before and after study. Mean monthly seizures and inter‐seizure periods obtained from contemporaneous seizure diaries in the 6 months before implantation were compared with 0 to 6 months, 7 to 12 months, and subsequent 12‐month periods after implantation. The number of dogs with >50% decrease in seizure frequency, >3 times increase in inter‐ictal period interval, and seizure freedom for >3 months at the time of death or last follow‐up were recorded.ResultsFive of 12 dogs were euthanized <12 months after implantation. All 7 remaining dogs showed >50% decrease in seizure frequency until last follow‐up, starting at a median of 37 to 48 months after implantation (range, 0‐6 to 61‐72 months) and a >3‐fold increase in mean inter‐seizure interval starting a median of 25 to 36 months after implantation (range, 0‐6 months to 49‐60 months), 3/7 dogs were seizure‐free at death or last follow‐up.Conclusions and Clinical ImportanceMonthly seizure frequencies decreased and inter‐seizure intervals increased in all dogs 2 to 3 years after VNS implantation, but a high proportion were euthanized before this time point. Prospective clinical trials are required to establish causality and the magnitude of this association.