AUTHOR=Ebrahimzadeh Elias , Shams Mohammad , Seraji Masoud , Sadjadi Seyyed Mostafa , Rajabion Lila , Soltanian-Zadeh Hamid 

TITLE=Localizing Epileptic Foci Using Simultaneous EEG-fMRI Recording: Template Component Cross-Correlation

JOURNAL=Frontiers in Neurology

VOLUME=Volume 12 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/neurology/articles/10.3389/fneur.2021.695997

DOI=10.3389/fneur.2021.695997

ISSN=1664-2295

ABSTRACT=Conventional EEG-fMRI methods have been proven to be of limited use in the sense that they cannot reveal the information existing in between the spikes. To resolve this issue, the current study obtains the time series of the epileptic components detected on EEG and uses them to fit the Generalized Linear Model (GLM), as a substitution for classical regressors. This approach allows for more precise localization, and equally importantly, the prediction of the future behavior of the epileptic generators.  The proposed method approaches the localization process in the source domain (component), rather than the electrode domain (EEG), and localizes the generators through investigating the spatial correlation between the spike template and the candidate components, as well as the medical records of the patient. To evaluate the contribution of EEG-fMRI and concordance between EEG and fMRI, this method was performed on 30 patients with refractory epilepsy. The results demonstrated the significant numbers of 29 and 24 for concordance and contribution, respectively, which marks a rise as compared to the existing literature. This study also shows that while conventional methods often fail to properly localize the epileptogenic zones that are located in deep brain structures, the proposed method can be of particular use.  For further evaluation, the concordance level between SOZ and IED-related BOLD clusters has been quantitatively investigated for different brain structures. Therefore, the distance between the BOLD clusters and IED/SOZ locations was measured in all patients. The results showed the superiority of the proposed method in delineating the spike-generating network compared to more conventional EEG-fMRI approaches. In all, the proposed method goes beyond the conventional methods by breaking the dependency on inside-the-scanner spikes and using the outside-the-scanner spike templates and the selected components, instead; achieving an accuracy of as high as 97%. Doing so, this method contributes to improving the yield of EEG-fMRI and creates a more realistic perception of the neural behavior of epileptic generators which is almost without precedent in the literature.