Localization of Epileptic Foci Based on Simultaneous EEG-fMRI Data

Area of Science:

• Neuroscience
• Medical Imaging
• Epileptology

Background:

• Functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) are key non-invasive techniques for studying brain activity.
• Combining EEG and fMRI offers a powerful method to investigate the correlation between electrical and hemodynamic brain responses.
• Epilepsy diagnosis and treatment planning, particularly pre-surgical evaluation, can benefit from advanced neuroimaging techniques.

Purpose of the Study:

• To review recent advancements in simultaneous EEG-fMRI methods for mapping brain regions and networks in focal epilepsy.
• To explore the application of EEG-fMRI in pre-surgical evaluation for localizing epileptiform activity.
• To discuss the methodologies, challenges, and findings of EEG-fMRI studies in various epilepsy types.

Main Methods:

• Simultaneous recording of EEG and fMRI data within a scanner.
• Advanced artifact removal techniques specific to EEG-fMRI.
• Statistical analysis of fMRI data using general linear model (GLM) with EEG-derived regressors, often involving convolution with a hemodynamic response function (HRF).

Main Results:

• EEG-fMRI successfully maps brain regions and networks involved in focal epileptic seizure generation.
• Interictal epileptiform discharges (IEDs) identified via EEG can be localized in the fMRI BOLD signal.
• Findings indicate that brain regions affected by IEDs may extend beyond the seizure generation site, helping to delineate the seizure onset zone (SOZ).

Conclusions:

• Simultaneous EEG-fMRI is a valuable clinical tool for pre-surgical epilepsy evaluation.
• The technique provides crucial information for localizing the SOZ and understanding seizure network involvement.
• EEG-fMRI aids in assessing patients with refractory epilepsy considered for surgical intervention.