Localizing confined epileptic foci in patients with an unclear focus or presumed multifocality using a...

Area of Science:

• Neuroscience
• Medical Imaging
• Epileptology

Background:

• Precise localization of epileptic foci is crucial for successful epilepsy surgery.
• Simultaneous electroencephalography-functional magnetic resonance imaging (EEG-fMRI) offers improved focus detection compared to single modalities but has limitations.
• Patients with unclear or multifocal epilepsy often face challenges in surgical candidacy due to localization difficulties.

Purpose of the Study:

• To assess the added value of a component-based EEG-fMRI approach in presurgical evaluation for complex epilepsy cases.
• To identify neural generators of epileptic activity using a component-based method for improved source localization.
• To compare the efficacy of component-based EEG-fMRI with conventional methods in patients ineligible for surgery due to unclear foci or presumed multifocality.

Main Methods:

• Adult epilepsy patients with unclear foci or presumed multifocality underwent simultaneous EEG-fMRI.
• A component-based approach was employed to analyze interictal epileptiform discharges (IEDs).
• Identified components-of-interest served as input for a generalized linear model (GLM), replacing classical regressors.

Main Results:

• Component-based EEG-fMRI identified significant BOLD responses topographically related to IEDs in 8 out of 9 patients.
• Localization was improved in 5 out of 6 patients with unclear foci.
• In presumed multifocal cases, the method identified a primary focus in 5 patients and confirmed multifocality in 1 patient.
• Intracranial EEG corroborated EEG-fMRI findings in 2 patients, supporting surgical candidacy.

Conclusions:

• Component-based EEG-fMRI significantly enhances source localization accuracy in complex epilepsy cases.
• This method provides more realistic localization estimations than conventional EEG-fMRI, aiding surgical decisions.
• Component-based EEG-fMRI is a valuable tool for pre-surgical evaluation, improving outcomes for patients with refractory epilepsy.