Abstract
Background: Electric and magnetic source imaging methods (ESI, MSI) estimate the location in the brain of the sources generating the interictal epileptiform discharges (II-ESI, II-MSI) and the ictal activity (IC-ESI, IC-MSI). These methods provide potentially valuable clinical information in the presurgical evaluation of patients with drug-resistant focal epilepsy, evaluated for surgical therapy. In spite of the significant technical advances in this field, and the numerous papers published on clinical validation of these methods, ESI and MSI are still underutilized in most epilepsy centers performing a presurgical evaluation. Our goal was to review and summarize the published evidence on the diagnostic accuracy of interictal and ictal ESI and MSI in epilepsy surgery.Methods: We searched the literature for papers on ESI and MSI that specified the diagnostic reference standard as the site of resection and the postoperative outcome (seizure-freedom). We extracted data from the selected studies, to calculate the diagnostic accuracy measures.Results: Our search resulted in 797 studies; 48 studies fulfilled the selection criteria (25 ESI and 23 MSI studies), providing data from 1,152 operated patients (515 for II-ESI, 440 for II-MSI, 159 for IC-ESI, and 38 for IC-MSI). The sensitivity of source imaging methods was between 74 and 90% (highest for IC-ESI). The specificity of the source imaging methods was between 20 and 54% (highest for II-MSI). The overall accuracy was between 50 and 75% (highest for IC-ESI). Diagnostic Odds Ratio was between 0.8 (IC-MSI) and 4.02–7.9 (II-ESI < II-MSI < IC-ESI).Conclusions: Our systematic review and meta-analysis provides evidence for the accuracy of source imaging in presurgical evaluation of patients with drug-resistant focal epilepsy. These methods have high sensitivity (up to 90%) and diagnostic odds ratio (up to 7.9), but the specificity is lower (up to 54%). ESI and MSI should be included in the multimodal presurgical evaluation.
Highlights
RationaleIn spite of the numerous published papers on the accuracy of electric source imaging (ESI) and magnetic source imaging (MSI) in localizing interictal epileptiform discharges and ictal activity, these methods have gained only partial acceptance in the presurgical evaluation of patients with drug-resistant focal epilepsy
Interictal epileptiform discharges and ictal activity are typically recorded during long-term video EEG monitoring, which is part of the presurgical evaluation in almost all centers
Interictal epileptiform discharges and ictal activity are essential components of the multimodal presurgical evaluation: they indicate the location of the irritative zone and the seizureonset zone, respectively
Summary
In spite of the numerous published papers on the accuracy of electric source imaging (ESI) and magnetic source imaging (MSI) in localizing interictal epileptiform discharges and ictal activity, these methods have gained only partial acceptance in the presurgical evaluation of patients with drug-resistant focal epilepsy. Interictal epileptiform discharges and ictal activity are essential components of the multimodal presurgical evaluation: they indicate the location of the irritative zone and the seizureonset zone, respectively Their accurate localization is extremely important for identifying the cortical area that needs to be surgically resected in order to render the patient seizurefree (2). Electric and magnetic source imaging methods (ESI, MSI) estimate the location in the brain of the sources generating the interictal epileptiform discharges (II-ESI, II-MSI) and the ictal activity (IC-ESI, IC-MSI) These methods provide potentially valuable clinical information in the presurgical evaluation of patients with drug-resistant focal epilepsy, evaluated for surgical therapy. Our goal was to review and summarize the published evidence on the diagnostic accuracy of interictal and ictal ESI and MSI in epilepsy surgery
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