[EEG-fMRI studies on the neural networks of the generalized spike and wave discharges: an overview]

This paper generalizes the seizures characterized with paroxysmal generalized spike and wave discharges (GSWDs) in the EEG. Recent studies showed that GSWDs disrupt specific neural networks only rather than the entire brain homogenously. Simultaneous EEG and functional MRI (EEG-fMRDI) provides a high spatiotemporal resolution method for uncovering the regions of the brain showing changes in metabolism and blood flow during epileptic activity. Human EEG-fMRI studies to date have revealed the blood oxygenation level dependent (BOLD) signal changes in response to GSWDs in some specific brain regions. Most studies have noted similar BOLD signals decrease in the bilateral cortical regions including frontal, frontal-parietal, posterior cingulated and precuneus cortex, as well as in the basal ganglia, and BOLD signals increase in the bilateral thalamic. Further studies demonstrated that BOLD signals in different regions were dynamic changes in the time course of GSWDs and BOLD changes in the cortical areas occurred before in the thalamus. These cortical-subcortical structures may form the neural networks associated with GSWDs generation and maintenance. More sophisticated analytic techniques will be developed to explore the BOLD time-course of GSWDs and identify the brain structures involved in seizure onset and discharges propagation respectively. The sub-network associated with different behavioral deficits between interical and ictal GSWDs, and the different subtypes of generalized seizures will be further studied. The functional connectivity of the nodes of the neural network of GSWDs can also be further investigated. A better understanding of the neural network responsible for GSWDs generation may help to develop new therapeutic interventions.