Abstracts

Rationale: Vagal nerve stimulation (VNS) is a well recognized procedure for refractory epilepsy in children. The number of non functional devices is a reality in some epilepsy centers for different reasons; lack of funding for a second operation, family views on the device, concerns on recurrent surgeries and other different motives. This is of importance as the main reason for the implantation is intractable epilepsy. We wanted to evaluate the seizure recurrence rate once the device becomes non-functional. Methods: We evaluated pediatric patients in 2 different epilepsy centers (Texas and Mexico). We included 15 patients with a non-functional device. All Patients were implanted with a VNS stimulator for recurrent intractable seizures, all the patients had a significant seizure reduction after the device was fully functional at 1-year post-implantation. We included cases with a proven non functional stimulator defined as at least 6 months with no response to interrogation of the implant. We recorded the average number of seizures before the original operation, during the active VNS therapy and after the stimulator was not responsive to programing and or interrogation. Results: All the patients were non-functional for at least a 6-month period. The seizure frequency was characterized as pretreatment baseline with initial reduction of more than 40 % events after the VNS initiation (100 % of the patients). No abrupt change in the seizure frequency was seen in 80 % of the cases after the non-functional stage. A gradual seizure increment was observed in almost all the patients in the short term. a plateau phase was seen with no further increase in events over the next 6-12 months, a long-term stage was defined after 12 months of non-functionality. The final seizure recurrence frequency was 20 to 30 % increase of the pre-surgical phase baseline. Conclusions: The risk of seizure recurrence after the device becomes non-functional can be divided into short and long-term outcomes, a feature that was not discussed in the past. The increase in the seizure frequency was in both groups never similar to the baseline pre-operation rate. Further studies of seizure recurrence are needed for functional-again devices. Funding: None