Long-term evaluation of synchronization between scalp EEG signals in partial epilepsy

For the anticipation of epileptic seizures synchronization between signals from intracranial recorded EEG has been studied. Here, we present our first findings for scalp EEG. For 3 epilepsy patients 85 hours of scalp EEG were analyzed. After determining the instantaneous phase with the Hilbert transform, the level of synchrony was calculated for all possible electrode pairs within 4 defined groups. This was done for 14 frequency bands of 2Hz between 1 and 50Hz. As well during sleep as in the awake state we found a particular behavior of the synchrony levels in the pathological hemisphere. Furthermore, we found a similar sleep-wake cycle for the two temporal lobe epilepsy patients, not seen in the case of the patient with extra temporal lobe epilepsy. These results show an altered brain dynamics for epilepsy patients, which can give information on the localization of the epilepsy.