Abstracts

True anterior temporal electrodes (TATEs, T[sub]1[/sub] and T[sub]2[/sub]) are as effective as mini-sphenoidal electrodes, and significantly superior to anterior temporal electrodes (ATEs, F[sub]7[/sub] and F[sub]8[/sub]) to detect epileptiform discharges. In addition, non-invasiveness makes TATEs more useful in clinical application. Low Resolution Brain Electromagnetic Tomography (LORETA) is a mathematical model for the reconstruction of current source from digitalized scalp electroencephalography (EEG). Using LORETA, we investigated the current source distribution patterns of interictal spikes on TATEs and those on ATEs respectively, and tried to find the difference between them. In the each digital scalp EEG of epileptic patients showing the interictal spikes of maximum amplitude on T[sub]1[/sub], T[sub]2[/sub], F[sub]7[/sub] or F[sub]8[/sub], we selected the most typical spike. The EEGs of ten patients were enrolled for the spike on each electrode respectively. All the 40 patients were epileptics and had complex partial seizures. The EEG data were collected from 21 channels using an average reference montage. In each typical spike, one time frame showing the highest amplitude of global power field was selected and LORETA image was acquired using that time frame. The average LORETA images for each electrode were obtained respectively. The Statistical non-Parametric Map (SnPM) between spikes on T[sub]1[/sub] and those on F[sub]7[/sub], and the SnPM between the spikes on T[sub]2[/sub] and those on F[sub]8[/sub] were acquired. The current source density in the average LORETA image of T[sub]1[/sub] spikes were maximum in Brodmann areas (BAs) 20 and 21. That of T[sub]2[/sub] spikes were maximum in BAs 13 and 21. The current sources of T[sub]1[/sub] and T[sub]2[/sub] spikes were mainly located in the anterior temporal area, and rare in the frontal lobe. The current source density in average LORETA image of F[sub]7[/sub] spikes were maximum in BAs 21, 13, 45 and 46. That of F[sub]8[/sub] spikes were maximum in BAs 13, 21 and 11. The current sources of F[sub]7[/sub] and F[sub]8[/sub] spikes were mainly located in the anterior temporal area and it was also observed in the insular cortex and the inferior frontal area. The difference of current source density in the SnPM between T[sub]1[/sub] and F[sub]7[/sub] spikes was maximal in BA 22 and minimal in BA 45. That difference between T[sub]2[/sub] and F[sub]8[/sub] spikes was maximal in BA 29 and minimal in BA 6. Both of TATEs and ATEs may mainly reflect the current source of the anterior temporal area. The current source of the inferior frontal gyrus may be more easily detected by F[sub]7[/sub] than T[sub]1 [/sub]and that of the superior temporal gyrus by T[sub]1[/sub] than F[sub]7[/sub]. The current source of the superior frontal and precentral gyrus may be more easily detected by F[sub]8[/sub] than T[sub]2[/sub] and that of the posterior cingulate gyrus by T[sub]2[/sub] than F[sub]8[/sub]. Thus TATEs may have less influences of the current source of the frontal lobe and reflect the current source of the temporal area more specifically than ATEs.