A study on clinical usefulness of 3D EEG source localization analysis

Abstract

Rationale: Although many antiepileptic drugs have been developed, about 30% of patients with epilepsy are still resistant to drug therapy and a complete remission is rare even in well controlled patients. The most effective treatment for drug resistant epilepsy patients is an epilepsy surgery which resects epileptogenic zone. The outcome of surgery is dependent upon the accuracy of localization of epileptic focus. We developed a 3D EEG source analysis method and compared its result with those of presurgical evaluation and MEG results (magnetoencephalography). Methods: Long term high resolution EEG (50 patients, 10-10 system) and MEG (26 patients) were recorded in partial epilepsy patients. Electrode locations of EEG were digitized in 3D coordinate system for co-registration with patient's MRI. After creating a Boundary Element Model (BEM) realistic head model of each MRI data, we analyzed dipole sources of epileptiform discharges from both EEG and MEG signals. Further, the results of dipole source localizations were compared between MEG and EEG. In addition, the location of dipole sources of MEG and EEG were compared with the results of presurgical evaluations (video-EEG, brain MRI, SPECT, SISCOM, FDG-PET) and epilepsy surgery. Results: In 41 (85.4%) out of 50 patients, EEG source dipoles were well concordant to the final result of presurgical evaluation and partially concordant in 7. Two patients' dipoles were not correct or not visible. MEG was performed in 26 patients and only 21 of them showed MEG spikes (1 - 35 spikes per patient). MEG source analysis results were concordant to those of EEG source analysis in 18 of 21 (85.7%) and partially concordant in 3. Twelve patients had an epilepsy surgery and 6(50%) of them had Engel Class I outcome, 3(25%) classII, and 3(25%) class III. This result indicates 3D EEG source analysis is a useful technique compared to MEG. Conclusions: Because EEG system is available in all regions of South Korea, many hospitals can record EEG and perform 3D EEG source analysis. This 3D EEG source analysis technique is found to be useful for localizing seizure focus and is recommended to be applied to the presurgical evaluation of the epilepsy surgery. (Figure Presented).