Effect of interictal epileptiform discharges on EEG coherence and phase lag in patients with focal epilepsy

Abstract

‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬ ‫ــــــــــــــــــــــــ‬ Background and Aim:Epilepsy is a network disease, and its pathological networks could be related to the interictal epileptiform discharges (IEDs). The aim is to explore the effect of IEDs on EEG functional connectivity metrics (coherence and phase lag degree) in patients with focal epilepsy. Methods: The study included 14 patients with focal epilepsy and 14 matched healthy controls. EEGs of the patients were segmented into two-second epochs: a. epochs containing IEDs, b. resting epochs with no IEDs. The selected epochs were analyzed using Fast Fourier Transform to yield four frequency bands: Delta, Theta, Alpha and Beta. Coherence and phase lag degree were computed between the EEG electrodes and were assessed at the intra-hemispheric (frontal-parietal and frontaltemporal) and inter-hemispheric (frontal, temporal and