Quantification of the spatio-temporal dynamics of the scalp EEG of epileptic patients

Epilepsy is a neurological disorder characterized by events called seizures. A seizure occurs when a massive group of neurons in the cerebral cortex begins to discharge in a highly organized rhythmic pattern and this causes an abnormal synchronization of the bioelectric fields impressed by the critical neuronal sources. In the literature there are some results, from intracranial EEG (IEEG) recorded in patients affected with intractable temporal lobe epilepsy, that show that by estimating the Short Term Maximum Lyapunov exponent (STLmax) and the convergence of the STLmax profiles of the critical electrode sites, we can quantify the entrainment of the neuronal sources. In other words we can monitor the synchronization of the chaotic activity of the sources and forecast the epileptic event. The spatial resolution of IEEG outdoes the resolution of scalp EEG and it is less sensitive to artifacts. Neverthless, we aim to estimate the entrainment from scalp EEG due to the invasiveness of IEEG. In this paper we present the analysis of the entrainment from scalp EEG recorded in three patients affected with different kind of epilepsy: the technique succeeded in extracting information about the entrainment of the critical neuronal sources.