Abstracts

To determine the overall utility of MEG in patients with temporal lobe epilepsy (TLE) and to evaluate the equivalence of MEG compared with invasive V-EEG. 33 patients with drug resistant TLE were evaluated at the Epilepsy Monitoring Unit in the University Texas Comprehensive Epilepsy Program from 1999 to 2001 and underwent epilepsy surgery. The intracranial subdural electrodes or grid placement was tailored for each patient. MEG-recordings were performed with a 148-channel whole-head MEG system.
Interictal epileptiform events were identified visually, while estimation of the location of their intracranial sources was performed using the single dipole model (ECD). ECD locations were superimposed on the patients[apos] MRI.
The epileptogenic region predicted by invasive V-EEG and MEG was defined in relation to the resected area (perfectly overlapping, partially overlapping, or non-overlapping). The correctness of prediction of the localization area was defined in regard to postoperative seizure outcome. Using MEG, we were able to localize the resected region correctly in a slightly greater proportion of patients (66.7%) than with invasive V-EEG (54.5%). MEG contributed to the localization of the resected region in 72.7% of patients for whom V-EEG only partially identified the resected zone. Overall, MEG and V-EEG results were equivalent in 54.5%. Additional localization information was obtained using MEG in 46% of the patients. MEG is a powerful tool in presurgical epilepsy evaluation of patients with TLE; it is most useful in patients with partially localizing V-EEG results. (Supported by Austrian Science Fund (Project J2224) and NIH-Grant (NS37941).)