Non-invasive studies to predict regions of seizure onset are important for planning intracranial grid locations for invasive cortical recordings prior to resective surgery for patients with medically intractable epilepsy. The neurosurgeon needs to know both the seizure onset zone (SOZ) and the region of immediate cortical spread to determine the epileptogenic zone to be resected. The immediate zone of spread may be immediately adjacent, on a nearby gyrus, in a different lobe, and sometimes even in the contralateral cerebral hemisphere. We reviewed consecutive simultaneous EEG/MEG recordings on 162 children with medically intractable epilepsy. We analyzed the MEG signals in the bandwidth 20–70 Hz with a beamformer algorithm, synthetic aperture magnetometry, at a 2.5 mm voxel spacing throughout the brain (virtual sensor locations, VSLs) with the kurtosis statistic (g2) to determine presence of excess kurtosis (γ2) consistent with intermittent increased high frequency spikiness of the background. The MEG time series was reconstructed (virtual sensor signals) at each of these VSLs. The VS signals were further examined with a relative peak amplitude spike detection algorithm. The time of VS spike detection was compared to the simultaneous EEG and MEG sensor signals for presence of conventional epileptiform spike morphology in the latter signals. The time of VS spike detection was compared across VSLs to determine earliest and last VSL to show a VS spike. Seven subjects showed delay in activation across VS locations detectable on visual examination. We compared the VS locations that showed earliest and later VS spikes with the locations on intracranial grid locations by electrocorticography (ECoG) that showed spikes and both onset and spread of seizures. We compared completeness of resection of VS locations to postoperative outcome. The VS locations for spike onset and spread were similar to locations for ictal onset and spread by ECoG.
Keywords: magnetoencephalography, beamformer, children, adolescents, intracranial EEG, outcome, network, localization
Citation: Rose DF, Fujiwara H, Holland-Bouley K, Greiner HM, Arthur T and Mangano FT (2013) Focal peak activities in spread of interictal-ictal discharges in epilepsy with beamformer MEG: evidence for an epileptic network? Front. Neurol. 4:56. doi: 10.3389/fneur.2013.00056
Received: 19 February 2013; Accepted: 30 April 2013;
Published online: 14 May 2013.
Edited by:Don Tucker, Electrical Geodesics, Inc. and the University of Oregon, USA
Reviewed by:Marino M. Bianchin, Universidade Federal do Rio Grande do Sul, Brazil
Copyright: © 2013 Rose, Fujiwara, Holland-Bouley, Greiner, Arthur and Mangano. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in other forums, provided the original authors and source are credited and subject to any copyright notices concerning any third-party graphics etc.
*Correspondence: Douglas F. Rose, Division of Neurology, Department of Pediatrics, Cincinnati Children’s Hospital Medical Center, 3333 Burnet Avenue, ML11006, Cincinnati, OH 45229, USA. e-mail: email@example.com