Ictal EEG source imaging and connectivity to localize the seizure onset zone in extratemporal lobe epilepsy

• Published in: Seizure (London, England) England), 2020-05, Vol.78, p.18-30
• Main Authors: Vespa, Simone, Baroumand, Amir G., Ferrao Santos, Susana, Vrielynck, Pascal, de Tourtchaninoff, Marianne, Feys, Odile, Strobbe, Gregor, Raftopoulos, Christian, van Mierlo, Pieter, El Tahry, Riëm
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Automated ESI; Cerebral Cortex - physiopathology; Child; Connectome - methods; Connectome - standards; Drug Resistant Epilepsy - diagnosis; Drug Resistant Epilepsy - physiopathology; Drug Resistant Epilepsy - surgery; Electrical source imaging; Electroencephalography - methods; Electroencephalography - standards; Epilepsies, Partial - diagnosis; Epilepsies, Partial - physiopathology; Epilepsies, Partial - surgery; Female; Follow-Up Studies; Functional connectivity; Granger causality; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Presurgical evaluation; Sensitivity and Specificity; Young Adult
• ISSN: 1059-1311; 1532-2688
• DOI: 10.1016/j.seizure.2020.03.001

•An automated algorithm was implemented for ictal ESI and subsequent connectivity from low-density EEG.•Connectivity analysis may improve the localization of the seizure onset zone in extratemporal lobe epilepsy.•Good localization was obtained also from diffuse hemispheric or bilateral ictal patterns. To evaluate the yield of Functional Connectivity (FC) in addition to low-density ictal Electrical Source Imaging (ESI) in extratemporal lobe epilepsy (ETLE), using an automated algorithm for analysis. Long-term EEG monitoring of consecutive ETLE patients who underwent surgery was reviewed by epileptologists, and seizure onsets characterized by rhythmical activity were identified. A spectrogram-based algorithm was developed to select objectively the parameters of ESI analysis. Two methods for SOZ localization were compared: i) ESI power, based on LORETA exclusively; ii) ESI + FC, including a Granger causality-based connectivity analysis. Results were determined at a sublobar level. The resection zone, in relation to 1-year follow-up surgical outcome, was considered as reference standard for diagnostic accuracy analyses. Ninety-four seizures from 24 patients were analyzed. At seizure-level, ESI power showed 36 % sensitivity and 72 % specificity (accuracy: 45 %). ESI + FC significantly improved the accuracy, with 52 % sensitivity and 84 % specificity (accuracy: 61 %, p = 0.04). Results of ESI + FC were equally valuable in patients with lateralized or bilateral/generalized visual interpretation of ictal EEG. In a patient level sub-analysis, upon blinded clinical interpretation, ESI + FC showed a correct localization in 67 % of patients and substantial inter-rater agreement (kappa = 0.64), against 27 % achieved by ESI power, with fair inter-rater agreement (kappa = 0.37). FC significantly improves SOZ localization compared to ESI solely in ETLE. Ictal ESI + FC could represent a novel option in the armamentarium of presurgical evaluation, aiding also in patients with visually non-localizable scalp ictal EEG. Prospective studies evaluating the clinical added value of automated low-density ictal ESI may be justified.