Abstract

One of the most important goals of the presurgical evaluation in refractory focal epilepsy is to define the epileptogenic zone (EZ), the area indispensable for the generation of epileptic seizures Since Electroencephalography (EEG) signal contains temporal information and fMRI carries spatial information, we can reasonably expect that a combination of the two contributes greatly to precise localization of epileptic focuses. With that in mind, we have first extracted spike patterns from outside of scanner EEG, through detecting and averaging the Interictal Epileptiform Discharges (IED). Then, having implemented the correlation between the identified pattern and inside-scanner EEG, an automated system was developed to extract the temporal information when an epileptic seizure is triggered. We proceeded to convolve the obtained regressor with the Hemodynamic Response Function (HRF) using the General Linear Model (GLM) for the purpose of localizing the epileptic focus. This study was conducted on 5 medication-resistant patients with epilepsy whose data was recorded in the National Brain Mapping Lab (NBML). The results of the proposed method are in line with the information provided in EEG for each of the 5 patients, and for the 3 patients who were candidates for brain surgery, they provided further information. The results suggest a significant improvement in localization accuracy and precision compared to existing methods in the literature.

Keywords: Simultaneous EEG-fMRI; Epilepsy; Independent Component Analysis (ICA); Blood Oxygen Level Dependent Imaging (BOLD); Generalized Linear Model (GLM)