Abstracts

Previous studies have shown that even during interictal intervals the seizure generating area of the brain exhibits an higher degree of synchronization than other brain areas. We investigated whether a multivariate phase synchronization cluster analysis is capable of capturing the epileptic focus by analyzing EEG recordings of interictal intervals in patients with neocortical lesional epilepsies (NLE)., Using a moving-window technique we analyzed long-lasting (up to several days) multichannel ECoG data that were recorded interictally in up to now four patients that underwent presurgical evaluation. Using our previously proposed measure (mean phase coherence) we investigated the level of synchronization between all pairs of electrodes (typically from grids with 32 or 64 contacts). The information content of the resulting synchronization matrix was reduced by applying an eigenvalue decomposition approach revealing spatial-temporal synchronization clusters., In all cases investigated so far we observed multiple synchronization clusters that varied in space and time during the recordings. Averaging the most dominant cluster structures over time at least one cluster could be identified whose spatial distribution correctly indicated the spatial extent of the epileptic focus as determined by the presurgical workup and the postoperative complete seizure control. Moreover, in some cases we observed additional clusters which pointed to functionally relevant brain areas located nearby (such as motor strip or language areas)., Identifying synchronization clusters in interictal ECoG recordings might proof helpful in the localization of the epileptic focus and its delineation from functionally relevant areas during presurgical evaluation., (Supported by Deutsche Forschungsgemeinschaft.)