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نمایش مقاله

Title:

Advancing Non-Invasive Presurgical Evaluation: A Component-Based EEG-fMRI Framework for Quantifying Localization Concordance in Focal Epilepsy

Subject:

Brain Mapping Applications in Epilepsy – Across Pediatric and Adult Populations

Presenter Author:
Name:	Elias Ebrahimzadeh

Author:
Name 1:	Elias Ebrahimzadeh - Corresponding - Presenter
Affiliation 1:	School of Cognitive Sciences, Institute for Research in Fundamental Sciences, Tehran, Iran, School of Electrical and Computer Engineering, College of Engineering, University of Tehran, Tehran, Iran.

Name 2:	Mostafa Asgarinejad
Affiliation 2:	Department of Cognitive Psychology, Institute for Cognitive Science Studies, Tehran, Iran

Name 3:	Melika Akbarimehr
Affiliation 3:	Neuroscience Research Center, Faculty of Medicine, Qom University of Medical Sciences, Qom, Iran.

Name 4:	Hamid Soltanian-Zadeh
Affiliation 4:	School of Cognitive Sciences, Institute for Research in Fundamental Sciences, Tehran, Iran, School of Electrical and Computer Engineering, College of Engineering, University of Tehran, Tehran, Iran.

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Abstract

Original Research

introduction :

The precise localization of the seizure onset zone (SOZ) is a critical and non-negotiable prerequisite for successful surgical intervention in patients with drug-resistant focal epilepsy. While simultaneous electroencephalography and functional magnetic resonance imaging (EEG-fMRI) has emerged as a promising non-invasive tool for mapping the hemodynamic correlates of interictal epileptiform discharges (IEDs), its clinical utility remains constrained by methodological limitations. A significant gap exists in the quantitative, objective assessment of spatial agreement between the electrophysiological source of IEDs and the resultant blood-oxygen-level-dependent (BOLD) response. Furthermore, conventional analyses often fail to account for the confounding influence of heterogeneous pathophysiological factors, such as varied epileptic substrate morphology and IED propagation patterns. This study aimed to develop and validate a novel, component-based quantitative framework to rigorously measure this concordance, thereby improving the accuracy and reliability of SOZ delineation from non-invasive EEG-fMRI data.

Methods:

We introduce a novel component-based EEG-fMRI integration method designed to objectively quantify the spatial relationship between the epileptogenic focus identified by EEG and the BOLD response. The core of our approach involves measuring the Euclidean distance between the centroid of the most significant IED-related BOLD cluster (defined by the voxel with the maximal z-score) and the dipole location of the corresponding epileptic independent component, derived from EEG source imaging. These measurements are performed within each patient's native anatomical space using coregistered high-resolution 3D T1-weighted images for precise spatial normalization. This methodology was applied to a cohort of 17 patients with refractory focal epilepsy. Concordance was classified into three tiers based on physical distance: full concordance (<25 mm), partial concordance (25–50 mm), and discordance (>50 mm).

Results:

The distances between BOLD clusters and IED source dipoles were significantly different across the three concordance groups (P < 0.0001), validating the classification scheme. Our analysis demonstrated full concordance for 17 IED types, with a mean distance of 17.85 ± 4.69 mm. Partial concordance was observed in 4 cases (mean distance: 36.47 ± 8.84 mm). Notably, no cases were classified as discordant. This outcome—100% concordance (full or partial)—represents a substantial improvement over the variable concordance rates reported in the existing literature. Critically, our component-based method overcame the fundamental limitation of conventional spike-triggered analyses, which are dependent on the sparse and often elusive occurrence of visually identifiable IEDs during scanning. By extracting epileptic sources from continuous data, the method achieved an estimated SOZ localization accuracy of 97%, a marked advancement over prior studies.

Conclusion:

This study confirms a strong and quantifiable spatial relationship between IED-generating neuronal circuits and the hemodynamic responses they elicit in refractory epilepsy. The proposed component-based EEG-fMRI framework provides a robust, objective, and highly accurate metric for assessing this concordance. By offering superior localization accuracy and circumventing the dependency on in-scanner spikes, this method establishes itself as a reliable and clinically valuable non-invasive predictor of the SOZ. We therefore advocate for its integration into the standard pre-surgical evaluation paradigm for patients with medically resistant focal epilepsy, where it can enhance diagnostic confidence and inform surgical planning to improve patient outcomes.

Keywords:

EEG-fMRI; Seizure Onset Zone (SOZ); Concordance Refractory Epilepsy; Component-Based Analysis; Localization Accuracy