Electroencephalographic source imaging: a prospective study of 152 operated epileptic patients

Abstract

Electroencephalography is mandatory to determine the epilepsy syndrome. However, for the precise localization of the irritative zone in patients with focal epilepsy, costly and sometimes cumbersome imaging techniques are used. Recent small studies using electric source imaging suggest that electroencephalography itself could be used to localize the focus. However, a large prospective validation study is missing. This study presents a cohort of 152 operated patients where electric source imaging was applied as part of the pre-surgical work-up allowing a comparison with the results from other methods. Patients (n = 152) with >1 year postoperative follow-up were studied prospectively. The sensitivity and specificity of each imaging method was defined by comparing the localization of the source maximum with the resected zone and surgical outcome. Electric source imaging had a sensitivity of 84% and a specificity of 88% if the electroencephalogram was recorded with a large number of electrodes (128–256 channels) and the individual magnetic resonance image was used as head model. These values compared favourably with those of structural magnetic resonance imaging (76% sensitivity, 53% specificity), positron emission tomography (69% sensitivity, 44% specificity) and ictal/interictal single-photon emission-computed tomography (58% sensitivity, 47% specificity). The sensitivity and specificity of electric source imaging decreased to 57% and 59%, respectively, with low number of electrodes (<32 channels) and a template head model. This study demonstrated the validity and clinical utility of electric source imaging in a large prospective study. Given the low cost and high flexibility of electroencephalographic systems even with high channel counts, we conclude that electric source imaging is a highly valuable tool in pre-surgical epilepsy evaluation.

EEG source imaging of brain states using spatiotemporal regression

“…2). Although for the epileptic data we focus on the cluster with maximal activity, conforming to the clinical use of other EEG-or fMRI-based localizing techniques (Brodbeck et al, 2011;Grouiller et al, 2011), the neurophysiological significance of secondary clusters in terms of involvement in neuronal networks modulating epileptic activity is highly relevant and interesting, but it is not the scope of this paper. Secondary clusters might indeed be true positives when considering not only the epileptogenic network but also the localization of a putative focus amenable to surgery (Richardson, 2012).…”

“…Localization accuracy was measured as the Euclidean distance between the source distribution global maximum and the target area (Brodbeck et al, 2011). The target area was identified as the resected area or the area involved in the seizure onset zone on icEEG for patient S5b (the only case in which surgery was not performed).…”

Multimodal effective connectivity analysis reveals seizure focus and propagation in musicogenic epilepsy

“…Here we investigated epileptic networks in a patient with musicogenic seizures triggered by rap music using DCM in a multimodal approach consisting of hd-EEG/fMRI and simultaneous hd-EEG and MEG. While each of these methods alone has been shown to be able to localize epileptic activity (Brodbeck et al, 2011;Pataraia et al, 2005;Vulliemoz et al, 2009), we made use of their complementary nature to improve analyses with regards to localization accuracy and effective connectivity and assess if the modalities will give concordant results. fMRI is able to show hemodynamic changes in the whole brain time-locked to epileptic activity and is characterized by its very high spatial resolution, especially for sources deep in the brain.…”

Multiple synergistic effects of emotion and memory on proactive processes leading to scene recognition

“…Accordingly, the estimation of the neural 593 sources of the ERP signal using a linear distributed inverse space turned out to be more sensitive 594 to capture subtle changes related to the processing of the emotional content of the scenes, 595 compared to the topographical mapping analyses carried out using 128 channels (Esslen et al, 596 2004;Pascual-Marqui et al, 2002). This dissociation is not surprising though, given the 597 enhanced spatial sensitivity of distributed source localization methods (including sLORETA) that 598 enables to reveal subtle differences between experimental conditions, which may be otherwise 599 difficult to capture based on local amplitude measurements performed at the sensor level 600 (Brodbeck et al, 2011;Lantz et al, 2001;Michel and Murray, 2012). 601…”