Source localization of epileptiform discharges in childhood absence epilepsy using a distributed source model: a standardized, low-resolution, brain electromagnetic tomography (sLORETA) study

Localizing the source of epileptiform discharges in generalized epilepsy has been controversial for the past few decades. Recent neuroimaging studies have shown that epileptiform discharges in generalized epilepsy can be localized to a particular region. Childhood absence epilepsy (CAE) is the most common generalized epilepsy in childhood and is considered the prototype of idiopathic generalized epilepsy (IGE). To better understand electrophysiological changes and their development in CAE, we investigated the origin of epileptiform discharges. We performed distributed source localization with standardized, low-resolution, brain electromagnetic tomography (sLORETA). In 16 children with CAE, sLORETA images corresponding to the midpoint of the ascending phase and the negative peak of the spike were obtained from a total of 242 EEG epochs (121 epochs at each timepoint). Maximal current source density (CSD) was mostly located in the frontal lobe (69.4%). At the gyral level, maximal CSD was most commonly in the superior frontal gyrus (39.3%) followed by the middle frontal gyrus (14.0%) and medial frontal gyrus (8.7%). At the hemisphere level, maximal CSD was dominant in the right cerebral hemisphere (63.6%). These results were consistent at the midpoint of the ascending phase and the negative peak of the spike. Our results demonstrated that the major source of epileptiform discharges in CAE was the frontal lobe. These results suggest that the frontal lobe is involved in generating CAE. This finding is consistent with recent studies that have suggested selective cortical involvement, especially in the frontal regions, in IGE.