A network approach to investigate the bi-hemispheric synchrony in absence epilepsy

Objective: Our objective was to unravel the dynamics underlying spike-and-wave discharges (SWDs) characteristic for childhood absence epilepsy. Methods: SWDs were recorded for a cohort of 28 children using magnetoencephalography. Non-linear association analyses and a graph theoretical metric of local connectedness (LoC) were utilized in a sliding window starting one s before till four s after ictal onset. Results: A focal pattern of bilateral frontal and parietal areas with high LoC during the spikes alternated by generalized patterns during the waves was found for all children studied during generalization of the SWDs. In the interval preceding the generalization a focal parietal region was most often (16/28) encountered and less often an occipital (4/28), temporal (5/28) or frontal (3/28) region. 55% of the children with a parietal/occipital focal onset became seizure free after the administration of two anti-epileptic drugs, and only 12.5% with a temporal/frontal focal onset. Conclusions: The transition from the interictal to the ictal state is for some of the children characterized by dominant LoC at either the parietal/occipital and for others at the frontal/temporal region. Significance: The focal onset of the SWDs varies in location among the children with a clinical similar profile, who, however, seemingly are differing with regard to seizure control.