Abstract
Objective To determine the diagnostic accuracy and clinical utility of electromagnetic source imaging (EMSI) in presurgical evaluation of patients with epilepsy.
Methods We prospectively recorded magnetoencephalography (MEG) simultaneously with EEG and performed EMSI, comprising electric source imaging, magnetic source imaging, and analysis of combined MEG-EEG datasets, using 2 different software packages. As reference standard for irritative zone (IZ) and seizure onset zone (SOZ), we used intracranial recordings and for localization accuracy, outcome 1 year after operation.
Results We included 141 consecutive patients. EMSI showed localized epileptiform discharges in 94 patients (67%). Most of the epileptiform discharge clusters (72%) were identified by both modalities, 15% only by EEG, and 14% only by MEG. Agreement was substantial between inverse solutions and moderate between software packages. EMSI provided new information that changed the management plan in 34% of the patients, and these changes were useful in 80%. Depending on the method, EMSI had a concordance of 53% to 89% with IZ and 35% to 73% with SOZ. Localization accuracy of EMSI was between 44% and 57%, which was not significantly different from MRI (49%–76%) and PET (54%–85%). Combined EMSI achieved significantly higher odds ratio compared to electric source imaging and magnetic source imaging.
Conclusion EMSI has accuracy similar to established imaging methods and provides clinically useful, new information in 34% of the patients.
Classification of evidence This study provides Class IV evidence that EMSI had a concordance of 53%–89% and 35%–73% (depending on analysis) for the localization of epileptic focus as compared with intracranial recordings—IZ and SOZ, respectively.
Glossary
- BESA=
- Brain Electrical Source Analysis;
- cEMSI=
- combined electromagnetic source imaging;
- DSM=
- distributed source model;
- ECD=
- equivalent current dipole;
- ED=
- epileptiform discharge;
- EMSI=
- electromagnetic source imaging;
- ESI=
- EEG source imaging;
- FDG=
- 18F-fluorodeoxyglucose;
- FLAIR=
- fluid-attenuated inversion recovery;
- FN=
- false negative;
- FP=
- false positive;
- GLM=
- generalized linear model;
- ICR=
- intracranial recording;
- IZ=
- irritative zone;
- MDT=
- multidisciplinary team;
- MEG=
- magnetoencephalography;
- MPRAGE=
- magnetization-prepared rapid-acquisition gradient echo;
- MSI=
- magnetoencephalography source imaging;
- NPV=
- negative predictive value;
- OR=
- odds ratio;
- PPV=
- positive predictive value;
- SOZ=
- seizure onset zone;
- TN=
- true negative;
- TP=
- true positive
Footnotes
Go to Neurology.org/N for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article.
↵* These authors contributed equally to this work.
The Article Processing Charge was funded by the Danish Epilepsy Centre, Filadelfia.
CME Course: NPub.org/cmelist
Class of Evidence: NPub.org/coe
- Received April 11, 2018.
- Accepted in final form October 2, 2018.
- Copyright © 2019 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Neurology.
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