Interictal magnetoencephalography in parietal lobe epilepsy - Comparison of equivalent current dipole and beamformer
Juha Wilenius1,2, Leena Lauronen1, Erika Kirveskari1
1HUS Medical Imaging Center, Clinical Neurophysiology, University of Helsinki and Helsinki University Hospital, Finland.
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.
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