EEG changes, recorded with subdural electrodes, after thiopental injections in patients with temporal lobe seizures

Abstract

Nineteen patients with temporal lobe epilepsy, examined with intracranial subdural electrodes for seizure monitoring, were subjected to intravenous thiopental injections to the level of deep narcosis. The induced EEG changes were recorded, analyzed, and correlated to the localization of the seizure-generating focus. In 14 patients with unilateral seizure onset, the thiopental injections evoked a focal spike activation on the focus side. The first suppression period in the EEG with a duration exceeding 1 s was recorded from the strip electrode overlying the focus. Only in six patients did asymmetries in the barbiturate-induced beta activity in the background EEG show lateralizing signs in concordance with the side of seizure onset. In five patients with bilateral seizure-generating foci, no significant lateralization in induced beta activity, focal spike activation, or focal suppression pattern could be found. The results are discussed, comparing similar studies performed with surface, sphenoidal, and depth electrodes.