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Ictal EEG Source Imaging in Frontal Lobe Epilepsy Leads to Improved Lateralization Compared With Visual Analysis

Kovac, Stjepana*,†; Chaudhary, Umair J.*; Rodionov, Roman*; Mantoan, Laura*; Scott, Catherine A.; Lemieux, Louis*; Wehner, Tim*; Scherg, Michael§; Diehl, Beate*,‡

Journal of Clinical Neurophysiology: February 2014 - Volume 31 - Issue 1 - p 10–20
doi: 10.1097/WNP.0000000000000022
Original Research
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Purpose: To investigate the utility of EEG source imaging to lateralize ictal patterns in frontal lobe epilepsy, which were nonlateralized by standard EEG analysis.

Methods: Prospective analysis of 17 seizures in 8 patients with unilateral frontal lobe epilepsy MRI lesions and nonlateralizing ictal scalp EEG. We applied four EEG source imaging techniques (phase maps, symmetric dipoles, low-resolution brain electromagnetic tomography analysis, and classical low-resolution brain electromagnetic tomography analysis recursively applied) to the averaged seizure pattern. We tested (1) the ability of these techniques to lateralize seizure patterns, (2) the agreement of the lateralization result with MRI lesion side and subdural EEG recordings, individually for each method and for concordance of all.

Results: We found lateralizing results in 5 of 17 seizures when analyzing phase maps, 8 of 17 when analyzing dipoles, and 5 of 17 in both classical low-resolution brain electromagnetic tomography analysis recursively applied and low-resolution brain electromagnetic tomography analysis. No discordance with the MRI lesion side was seen when analyzing phase maps, whereas dipole analysis was discordant to the MRI lesion in two seizures, classical low-resolution brain electromagnetic tomography analysis recursively applied in one, and low-resolution brain electromagnetic tomography analysis in two. Agreement between all imaging methods was found in three seizures (three patients), all in line with the side of the MRI lesion.

Conclusions: Advanced EEG review methods and source localization provide useful lateralizing information in difficult frontal lobe epilepsy seizure patterns.

*Institute of Neurology, National Hospital for Neurology and Neurosurgery, London, United Kingdom;

Department of Neurology, University of Muenster, Muenster, Germany;

Telemetry Unit, National Hospital for Neurology and Neurosurgery, London, United Kingdom; and

§BESA GmbH, Grafelfing/Munich, Germany.

Address correspondence and reprint requests to Stjepana Kovac, MD, Institute of Neurology, National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, United Kingdom; e-mail: stjepana.kovac.09@ucl.ac.uk.

S. Kovac was supported by a grant of the German Research Foundation (Deutsche Forschungsgemeinschaft; KO 3878/1-1). This work was undertaken at the University College London Hospitals (UCLH)/ University College London (UCL) that received a proportion of funding from the Department of Health's NIHR Biomedical Research Centers funding scheme. L. Lemieux received support of the Medical Research Council (grant G0301067). B. Diehl was supported by a HEFCE Clinical senior Lectureship award.

© 2014 by the American Clinical Neurophysiology Society