Electroencephalography–functional magnetic resonance imaging for clinical evaluation in focal epilepsy

Abstract

Abstract Objective We aimed to evaluate the contribution of simultaneous recording of electroencephalography–functional magnetic resonance imaging (EEG‐fMRI) in the diagnosis of epilepsy syndrome, localization of the epileptogenic zone (EZ), and decision‐making regarding surgical treatment. Methods We performed a retrospective study to evaluate patients with focal epilepsy who underwent EEG‐fMRI. Two evaluators assessed epilepsy syndrome, presumed focus, and surgical candidacy and defined confidence levels. They assessed these clinical characteristics first without EEG‐fMRI and then including EEG‐fMRI to assess how the results of EEG‐fMRI changed the evaluations. We also determined how the clinical evaluation was affected by the concordance level between the blood oxygen level‐dependent (BOLD) response and the presumed focus location, and by the confidence level of the BOLD response itself based on the t‐value of the primary and secondary clusters. Results Fifty‐one scans from 48 patients were included. The BOLD map affected 66.7% of the evaluations by altering evaluation items (epilepsy syndrome, presumed focus, or surgical candidacy) or their confidence levels. EEG‐fMRI results increased the confidence levels of epilepsy syndrome, presumed focus, or surgical candidacy in 47.1% of patients but reduced clinical confidence in these features in 11.8%. More specifically, the confidence levels increased for epilepsy syndrome in 28.5%, identification of presumed focus in 33.9%, and determination of surgical candidacy in 29.4%. The BOLD signal confidence level, whether high or low, did not influence these clinical factors. Significance Previous studies have emphasized the utility of EEG‐fMRI for the localization of the epileptogenic zone. This study demonstrated the potential of EEG‐fMRI to influence clinical confidence when determining epilepsy syndrome, the presumed epileptic focus, and surgical candidacy.

Keywords

• clinical evaluation
• decision making
• focal epilepsy
• simultaneous EEG‐fMRI
• surgical treatment