Preoperative localization of seizure onset zones by magnetic source imaging, EEG-correlated functional MRI, and their combination

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  • 1 Department of Neurosurgery,
  • 2 Sagol Brain Institute,
  • 3 Department of Neurology, and
  • 6 Department of Radiology, Tel Aviv Medical Center, Tel Aviv;
  • 4 Department of Neurology, Hadassah Medical Center, Jerusalem;
  • 5 Department of Neurosurgery, Rambam Health Care Campus, Haifa;
  • 7 Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv;
  • 8 Hebrew University Hadassah Medical School, Jerusalem; and
  • 9 Rappaport Faculty of Medicine-Technion, Haifa, Israel
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OBJECTIVE

Preoperative localization of seizure onset zones (SOZs) is an evolving field in the treatment of refractory epilepsy. Both magnetic source imaging (MSI), and the more recent EEG-correlated functional MRI (EEG-fMRI), have shown applicability in assisting surgical planning. The purpose of this study was to evaluate the capability of each method and their combination in localizing the seizure onset lobe (SL).

METHODS

The study included 14 patients who underwent both MSI and EEG-fMRI before undergoing implantation of intracranial EEG (icEEG) as part of the presurgical planning of the resection of an epileptogenic zone (EZ) during the years 2012–2018. The estimated location of the SL by each method was compared with the location determined by icEEG. Identification rates of the SL were compared between the different methods.

RESULTS

MSI and EEG-fMRI showed similar identification rates of SL locations in relation to icEEG results (88% ± 31% and 73% ± 42%, respectively; p = 0.281). The additive use of the coverage lobes of both methods correctly identified 100% of the SL, significantly higher than EEG-fMRI alone (p = 0.039) and nonsignificantly higher than MSI (p = 0.180). False-identification rates of the additive coverage lobes were significantly higher than MSI (p = 0.026) and EEG-fMRI (p = 0.027). The intersecting lobes of both methods showed the lowest false identification rate (13% ± 6%, p = 0.01).

CONCLUSIONS

Both MSI and EEG-fMRI can assist in the presurgical evaluation of patients with refractory epilepsy. The additive use of both tests confers a high identification rate in finding the SL. This combination can help in focusing implantation of icEEG electrodes targeting the SOZ.

ABBREVIATIONS DRE = drug-resistant epilepsy; EZ = epileptogenic zone; FCD = focal cortical dysplasia; fMRI = functional MRI; FP = false positive; icEEG = intracranial EEG; IED = interictal epileptiform discharge; MEG = magnetoencephalography; MSI = magnetic source imaging; SL = seizure onset lobe; SOZ = seizure onset zone.

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Contributor Notes

Correspondence Assaf Berger: Tel Aviv Medical Center, Tel Aviv, Israel. assaf.berger@gmail.com.

INCLUDE WHEN CITING Published online May 15, 2020; DOI: 10.3171/2020.3.JNS192794.

A.B., N.C., T.G., and I.S. contributed equally to this work.

Disclosures Dr. Medvedovsky reports being one of the authors of the patent related to the dual-array EEG-fMRI approach.

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