Abstracts

Rationale: Many studies have shown that refractory epilepsy may not be a focal but rather a network disease and that it may disrupt the organizing ability of resting-state brain networks. And smaller studies have found that vagus nerve stimulation(VNS) may control epileptic seizures, through modulation of both large-scale and regional functional connectivity. We evaluated the pre-operative PET data of VNS implanted pediatric patients with refractory epilepsy to compare and analyze the connectivity of the patients and its prognostic role in seizure control.  Methods: After a retrospective review of pediatric neurology patients who have implanted VNS at Severance Children’s Hospital, Seoul, from year 2004 to 2016, a total of 66 patients were collected for the study. All patients were evaluated with Fludeoxyglucose (18F) positron emission tomography (FDG-PET) prior to VNS insertion. Patients with follow up period shorter than one year after the procedure were excluded. We conducted an independent component analysis of FDG-PET to extract independent brain components and cross-sectional connectivity was analyzed.  Results: 54.54% (36 patients) of the patients showed more than 50% percent seizure reduction from baseline frequency after average 4.40 years of vagus nerve stimulation. 68.18% of the PET data were abnormal with focally, multi-focally or diffusely decreased metabolism and activity. When the patients were divided into more than 50% seizure control and less than 50% seizure control groups, a significant metabolic connectivity was noted in the first group. Their pre-op FDG-PETs showed relatively increased connection between the occipital area to bilateral central gyri, and Rt. parietal area to bilateral anterior temporal lobes in the group with 50% and higher seizure control compared to less than 50% control group.  Conclusions: This study shows PET imaging can be utilized as a prognostic factor for vagus nerve stimulation and may contribute in understanding the mechanism of VNS in controlling seizures. Funding: No funding was received in support of this abstract.