Interictal and Ictal MEG in presurgical evaluation for epilepsy surgery

Hermann Stefan,Stefan Rampp

doi:10.1186/s42494-020-00020-2

Hermann Stefan, Stefan Rampp

Open Access

https://doi.org/10.1186/s42494-020-00020-2

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Journal: Acta Epileptologica	Publication Date: Aug 4, 2020
Citations: 6	License type: open-access

Affiliation: Universitätsklinikum Erlangen

Abstract

Although presurgical evaluation of patients with pharamacoresistent focal epilepsies provides essential information for successful epilepsy surgery, there is still a need for further improvement. Developments of noninvasive electrophysiological recording and analysis techniques offer additional information based on interictal and ictal epileptic activities. In this review, we provide an overview on the application of ictal magnetoencephalography (MEG). The results of a literature research for published interictal/ictal MEG findings and experiences with own cases are demonstrated and discussed. Ictal MEG may provide added value in comparison to interictal recordings. The results may be more focal and closer to the invasively determined seizure onset zone. In some patients without clear interictal findings, ictal MEG could provide correct localization. Novel recording and analysis techniques facilitate ictal recordings. However, extended recording durations, movement and artifacts still represent practical limitations. Ictal MEG may provide added value regarding the localization of the seizure onset zone but depends on the selection of patients and the application of optimal analysis techniques.

Highlights

Epilepsy surgery is an effective treatment option in drug resistant focal epilepsies
The results showed concordant ictal MEG onset source localization and interictal MEG discharge source localizations in the same lobe, and the ictal localizations are closer than the interictal to the seizure onset zone (SOZ) defined by invasive seizure onset
Ictal MEG turned out positive in 25 of 31 seizures (80.6%) [35]. These findings indicated that earlyphase source analysis of interictal and ictal discharges will produce high density EEG (HDEEG)-MEG source solutions that better guide and limit reliance on invasive intracranial monitoring in the pre-surgical diagnosis

Summary

Introduction

Epilepsy surgery is an effective treatment option in drug resistant focal epilepsies. The ictal MEG provides clear unilateral source localizations even if interictal MEG spikes are bilateral or missing, and shows better concordance with intercerebral EEG of the SOZ at the sub-lobar level than the interictal MEG. Interictal MEG yielded multilobar localizations, including two with bilateral findings, whereas ictal MEG provided sublobar concordance with the resection in three of these. The rate of ictal/interictal concordance for MEG was better than that for EEG (90.32% vs 66.67%) and the interictal localizations were closer to the invasively determined seizure onset. Ictal MEG turned out positive in 25 of 31 seizures (80.6%) [35] These findings indicated that earlyphase source analysis of interictal and ictal discharges will produce high density EEG (HDEEG)-MEG source solutions that better guide and limit reliance on invasive intracranial monitoring in the pre-surgical diagnosis.

Findings

Discussion

Conclusion