Seizure Onset Zone Localization from Ictal High-Density EEG in Refractory Focal Epilepsy

Epilepsy surgery is the most efficient treatment option for patients with refractory epilepsy. Before surgery, it is of utmost importance to accurately delineate the seizure onset zone (SOZ). Non-invasive EEG is the most used neuroimaging technique to diagnose epilepsy, but it is hard to localize th...

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Bibliographic Details
Published in:Brain topography 2017-03, Vol.30 (2), p.257-271
Main Authors: Staljanssens, Willeke, Strobbe, Gregor, Holen, Roel Van, Birot, Gwénaël, Gschwind, Markus, Seeck, Margitta, Vandenberghe, Stefaan, Vulliémoz, Serge, van Mierlo, Pieter
Format: Article
Language:English
Subjects:
Adult
Algorithms
Biomedical and Life Sciences
Biomedicine
Brain - physiopathology
Electrodes
Electroencephalography - methods
Epilepsies, Partial - physiopathology
Female
Humans
Male
Middle Aged
Neuroimaging
Neurology
Neurosciences
Original Paper
Psychiatry
Seizures - physiopathology
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Summary:Epilepsy surgery is the most efficient treatment option for patients with refractory epilepsy. Before surgery, it is of utmost importance to accurately delineate the seizure onset zone (SOZ). Non-invasive EEG is the most used neuroimaging technique to diagnose epilepsy, but it is hard to localize the SOZ from EEG due to its low spatial resolution and because epilepsy is a network disease, with several brain regions becoming active during a seizure. In this work, we propose and validate an approach based on EEG source imaging (ESI) combined with functional connectivity analysis to overcome these problems. We considered both simulations and real data of patients. Ictal epochs of 204-channel EEG and subsets down to 32 channels were analyzed. ESI was done using realistic head models and LORETA was used as inverse technique. The connectivity pattern between the reconstructed sources was calculated, and the source with the highest number of outgoing connections was selected as SOZ. We compared this algorithm with a more straightforward approach, i.e. selecting the source with the highest power after ESI as the SOZ. We found that functional connectivity analysis estimated the SOZ consistently closer to the simulated EZ/RZ than localization based on maximal power. Performance, however, decreased when 128 electrodes or less were used, especially in the realistic data. The results show the added value of functional connectivity analysis for SOZ localization, when the EEG is obtained with a high-density setup. Next to this, the method can potentially be used as objective tool in clinical settings.
ISSN:0896-0267
1573-6792
DOI:10.1007/s10548-016-0537-8