CONTRIBUTION OF MAGNETOENCEPHALOGRAPHY TO THE PRESURGICAL DETERMINATION OF THE EPILEPTOGENIC ZONE IN PATIENTS WITH FRONTAL LOBE EPILEPSY
Abstract number :
2.222
Submission category :
Year :
2003
Submission ID :
2160
Source :
www.aesnet.org
Presentation date :
12/6/2003 12:00:00 AM
Published date :
Dec 1, 2003, 06:00 AM
Authors :
Ekaterina Pataraia, Panagiotis G. Simos, Rebecca L. Billingsley, Eduardo M. Castillo, Shirin Sarkari, Vijay Maggio, James W. Wheless, Michelle Fitzgerald, Breier I. Joshua, Andrew C. Papanicolaou Neurosurgery, University of Texas, Houston Medical Center,
Patients with extratemporal epilepsy pose major problems for epilepsy surgery. Especially in frontal lobe epilepsy (FLE), the variability of ictal and interictal electroencephalographic (EEG) findings makes determination of the epileptogenic zone very difficult. The purpose of the present study was to determine whether magnetoencephalography (MEG) can provide additional, helpful information toward this goal.
Recordings were performed with a 148-channel whole-head MEG system concurrently with 24-channel surface EEG in 18 patients with focal, drug-resistant FLE. All patients were evaluated at the Epilepsy Monitoring Unit in the University Texas Comprehensive Epilepsy Program from 1997 to 2001 and underwent epilepsy surgery. Fourteen patients had lesional and 4 patients had nonlesional FLE. Follow-up information was available for up to 12 months postoperatively. Interictal epileptiform events were identified visually, while estimation of the location of their intracranial sources was performed using the single equivalent dipole model (ECD). ECD locations were superimposed on the patients[apos] high resolution MRI.
Based on scalp-EEG alone, the epileptogenic zone was correclty identified in only 2 patients (11%), whereas in 3 patients (17%) the EEG-defined epileptogenic zone partially overlapped with the resected area. In the majority of cases (13 patients or 72%), scalp-EEG did not provide useful localization information.
On the basis of interictal MEG data, the epileptogenic zone was correclty identified in 11/18 patients (61%). In four patients (22%) MEG indicated that the irritable zone was more extensive, but included, the resected area (partially correct localization). Incorrect localization was achieved in only 2 cases. Thus adding the MEG results could significantly influence the ability to localize epileptogenic area, thereby potentially improving surgical outcome.
MEG provides accurate information regarding the irritable zone in as many as 61% of FLE patients with frequent interictal epileptiform activity. Futhermore, resection of the epileptogenic zone defined by MEG seems to have prognostic implications on postoperative seizure control.
[Supported by: NINDS grant NS37941 and the Austrian Science Fund (J2224).]