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. 2020 Mar 10:5:64-72.
doi: 10.1016/j.cnp.2020.02.003. eCollection 2020.

Interictal magnetoencephalography in parietal lobe epilepsy - Comparison of equivalent current dipole and beamformer (SAMepi) analysis

Juha Wilenius  1   2 , Leena Lauronen  1 , Erika Kirveskari  1 , Eija Gaily  3 , Liisa Metsähonkala  3 , Ritva Paetau  2
Affiliations

Interictal magnetoencephalography in parietal lobe epilepsy - Comparison of equivalent current dipole and beamformer (SAMepi) analysis

Juha Wilenius et al. Clin Neurophysiol Pract. .

Abstract

Objective: To evaluate a novel analysis method (SAMepi) in the localization of interictal epileptiform magnetoencephalographic (MEG) activity in parietal lobe epilepsy (PLE) patients in comparison with equivalent current dipole (ECD) analysis.

Methods: We analyzed the preoperative interictal MEG of 17 operated PLE patients utilizing visual analysis and: (1) ECD with a spherical conductor model; (2) ECD with a boundary element method (BEM) conductor model; and (3) SAMepi - a kurtosis beamformer method. Localization results were compared between the three methods, to the location of the resection and to the clinical outcome.

Results: Fourteen patients had an epileptiform finding in the visual analysis; SAMepi detected spikes in 11 of them. A unifocal finding in both the ECD and in the SAMepi analysis was associated with a better chance of seizure-freedom (p = 0.02). There was no significant difference in the distances from the unifocal MEG localizations to the nearest border of the resection between the different analysis methods.

Conclusions: Localizations of unifocal interictal spikes detected by SAMepi did not significantly differ from the conventional ECD localizations.

Significance: SAMepi - a novel semiautomatic analysis method - is useful in localizing interictal epileptiform MEG activity in the presurgical evaluation of parietal lobe epilepsy patients.

Keywords: Beamformer; Epilepsy surgery; Equivalent current dipole; Interictal; Magnetoencephalography; Parietal lobe.

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Conflict of interest statement

None.

Figures

Fig. 1
Fig. 1
Distances from the unifocal MEG localizations to the nearest border of the resection. Zero indicates a localization inside the resected area. Patients with an Engel class IV outcome are excluded.
Fig. 2
Fig. 2
MEG localizations in one seizure-free patient (#4). Localizations by the three different analysis methods illustrated on the postoperative MRI showing the resection of the right postcentral gyrus (outlined in green). Bottom right: MEG field pattern of the averaged spikes. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
See this image and copyright information in PMC

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