Effects of sevoflurane and isoflurane on electrocorticographic activities in patients with temporal lobe epilepsy

To compare the neuroexcitatory effects of sevoflurane and isoflurane, we re corded electrocorticograms (ECoG) during wakefulness and during sevoflurane and isoflurane anesthesia in six patients with temporal lobe epilepsy (TLE ). These patients had subdural grid electrodes chronically implanted in the temporal region. During sevoflurane anesthesia at 1.5 minimum alveolar con centration (MAC) of the combination with 67% nitrous oxide (N2O), a marked increase in interictal paroxysmal activities was observed in four patients. Two patients had a slight increase in paroxysmal activities. Activated are as were widely distributed, not being confined to the ictal onset zone of s pontaneous seizures. However, isoflurane anesthesia at 1.5 MAC of the combi nation with 67% N2O was associated with less increased paroxysmal activity. While the neuroexcitatory properties of sevoflurane proved greater than th ose of isoflurane, the widespread irritative. response to sevoflurane admin istration was not helpful in localizing the epileptogenic area.