Correlation between stereo-EEG, CT-scan and stereotactic biopsy data in epileptic patients with low-grade gliomas

Stereo-EEG activity, which was recorded precisely from the same location as stereotactic biopsies, was studied on 11 patients with low-grade glioma and severe partial epilepsy. The volume of the lesions varied from 6 to 72 cm3 (mean 23 cm3). A very depressed activity was recorded in all the 25 specimens of solid tumor and in more than half of infiltrated white matter. The background activity was still conserved in all 'normal' fragments, while it is never found in solid tumor; sometimes it could be found in the infiltrating tumors of white or gray matter. High voltage theta and delta activity was recorded in neither 'normal' nor solid tumors. We emphasize the importance of considering the stage of evolution when we evaluate the significance of the stereo-EEG activity.