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Mapping Epileptic Networks: IED-Triggered Hemodynamic Changes Identified via Simultaneous EEG-fMRI Recordings

Authors :

Elias Ebrahimzadeh¹ Mostafa Asgarinejad² Melika Akbarimehr³ Hamid Soltanian-Zadeh⁴

1- دانشگاه تهران دانشکده علوم مهندسی 2- موسسه آموزش عالی علوم شناختی 3- دانشگاه علوم پزشکی قم 4- دانشگاه تهران دانشکده علوم مهندسی

Keywords :

Simultaneous EEG-fMRI،Epilepsy،Independent Component Analysis (ICA)،Blood-oxygen-level dependent imaging (BOLD)،Generalized Linear Model (GLM)

Abstract :

A primary objective in presurgical evaluation for refractory focal epilepsy is the precise delineation of the epileptogenic zone (EZ)—the cortical area essential for seizure generation. Given that electroencephalography (EEG) provides superior temporal resolution while functional magnetic resonance imaging (fMRI) offers enhanced spatial localization, integrating these modalities holds significant promise for improving epileptic focus identification. In this study, we first derived characteristic spike patterns by detecting and averaging interictal epileptiform discharges (IEDs) from extraoperative EEG recordings. These patterns were then correlated with intracranial EEG data to develop an automated system for precise temporal mapping of seizure activity. Finally, we convolved the resulting temporal regressor with the hemodynamic response function (HRF) within a general linear model (GLM) framework to achieve robust localization of epileptic foci. This study was performed on five medication-resistant epilepsy patients whose neuroimaging and electrophysiological data were acquired at the National Brain Mapping Lab (NBML). Our proposed methodology demonstrated strong concordance with clinical EEG findings across all five cases. Notably, for the three surgical candidates, the approach provided additional localizing information beyond conventional EEG data. Quantitative analysis revealed statistically significant enhancements in both localization accuracy (p<0.05) and spatial precision (mean ± SEM: 2.3 ± 0.4 mm) compared to current gold-standard techniques reported in recent literature.