Abstracts

Rationale: The purpose of this study is to advance the understanding of the neurophysiologic mechanism of action of vagus nerve stimulation (VNS) for the treatment of epilepsy. Methods: Epileptic patients implanted with VNS underwent EEG and FDG-PET/CT studies during the following times: pre-implantation and at 6 months post-implantation. EEG power spectra and coherence were computed using the Thomson multi-taper method. For FDG-PET/CT imaging analysis, PMOD biomedical image quantification and kinetic modeling software was used to quantify each local standard uptake value. Results: With VNS in two patients, a significant reduction in power occurred in the most active electrodes. There was a reduction of coherence with VNS between the most active electrodes. FDG-PET showed a significant reduction in global and regional metabolism post-stimulation, i.e., in the bilateral temporal and bilateral thalamic regions for both patients. Conclusions: Significant changes in the power and coherence spectra, as well as in gobal and regional cerebral metabolism could reflect neuromodulation due to vagus nerve stimulation. Further studies in three more VNS patients with epilepsy are currently in progress. These results and analyses will be included in this presentation. Quantitative FDG-PET and EEG analyses provide complimentary neurophysiologic information which can further elucidate the mechanism(s) of action of neurostimulation therapies for epilepsy.