Neuroimaging and electroencephalographic changes after vagus nerve stimulation in a boy with medically intractable myoclonic astatic epilepsy

Myoclonic astatic epilepsy (MAE) is characterized by multiple seizure types, which are often refractory. Although vagus nerve stimulation (VNS) is an alternative treatment for medically intractable seizures, its exact mechanism of action remains unclear. Herein, we report the case of a 4-year-old boy with intractable MAE who has been in a seizure-free status for 2 years and 3 months since 6 months after the implantation of a vagus nerve stimulator (Model 103, Cyberonics, Inc., Houston, TX). Various test results 6 months after VNS were compared with those before VNS. Results of an electroencephalograph revealed disappearance of epileptiform discharges and an increased beta–gamma spectrum rhythm. The brain diffusion-tensor imaging showed an increased ratio of fraction anisotropy in the right fimbria–fornix, indicating improved diffusion of the white matter tract, and 18F-fluorodeoxyglucose positron emission tomography revealed globally improved cerebral glucose metabolism. His cognitive and social–emotional performances also improved at 2 years after VNS. To the best of our knowledge, this is the first report to describe the effects of VNS on fimbria–fornix and glucose metabolism in MAE.