Interictal intracranial electroencephalography for predicting surgical success: The importance of space and time

• Published in: Epilepsia (Copenhagen) Vol. 61; no. 7; pp. 1417 - 1426
• Main Authors: Wang, Yujiang, Sinha, Nishant, Schroeder, Gabrielle M., Ramaraju, Sriharsha, McEvoy, Andrew W., Miserocchi, Anna, Tisi, Jane, Chowdhury, Fahmida A., Diehl, Beate, Duncan, John S., Taylor, Peter N.
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01.07.2020
• Subjects: Computed tomography; Convulsions & seizures; cortical localization; Drug Resistant Epilepsy - diagnostic imaging; Drug Resistant Epilepsy - physiopathology; Drug Resistant Epilepsy - surgery; EEG; Electrodes; Electrodes, Implanted; Electroencephalography; Electroencephalography - methods; Epilepsy; epilepsy surgery; epileptogenic zone; Humans; intracranial electrodes; Localization; Magnetic resonance imaging; Magnetic Resonance Imaging - methods; Nerve Net - diagnostic imaging; Nerve Net - physiopathology; Nerve Net - surgery; Predictions; Predictive Value of Tests; Retrospective Studies; Seizures; Time Factors; Treatment Outcome; epilepsy surgery; epileptogenic zone; EEG; cortical localization; intracranial electrodes
• ISSN: 0013-9580; 1528-1167; 1528-1167
• DOI: 10.1111/epi.16580

Objective Predicting postoperative seizure freedom using functional correlation networks derived from interictal intracranial electroencephalography (EEG) has shown some success. However, there are important challenges to consider: (1) electrodes physically closer to each other naturally tend to be more correlated, causing a spatial bias; (2) implantation location and number of electrodes differ between patients, making cross‐subject comparisons difficult; and (3) functional correlation networks can vary over time but are currently assumed to be static. Methods In this study, we address these three challenges using intracranial EEG data from 55 patients with intractable focal epilepsy. Patients additionally underwent preoperative magnetic resonance imaging (MRI), intraoperative computed tomography, and postoperative MRI, allowing accurate localization of electrodes and delineation of the removed tissue. Results We show that normalizing for spatial proximity between nearby electrodes improves prediction of postsurgery seizure outcomes. Moreover, patients with more extensive electrode coverage were more likely to have their outcome predicted correctly (area under the receiver operating characteristic curve > 0.9, P « 0.05) but not necessarily more likely to have a better outcome. Finally, our predictions are robust regardless of the time segment analyzed. Significance Future studies should account for the spatial proximity of electrodes in functional network construction to improve prediction of postsurgical seizure outcomes. Greater coverage of both removed and spared tissue allows for predictions with higher accuracy.