Abstract: Objective To compare the effects of sevoflurane with different concentrations on the electroencephalogram(EEG) in epileptic or non-epileptic patients and investigate the suitable concentration of sevoflurane for epilepsy surgery.Methods The changes of epidural EEG were observed during anesthesia with 0.7, 1.0, 1.3 and 1.5 MAC sevoflurane in 20 epileptic patients undergoing epilepsy surgery and in 15 non-epileptic patients of neurosurgery.Results The frequencies of spike (or sharp) waves were similar at 0.7, 1.0 and 1.3 MAC, and increased significantly at 1.5 MAC in epileptic patients. No spike waves appeared at 0.7, 1.0 and 1.3 MAC and five cases showed spike bursts at 1.5 MAC in non-epileptic patients. The frequencies of α and β waves decreased and δ wave increased with the increases of sevoflurane concentration in both epileptic and non-epileptic patients.Conclusion The maintenance of anesthesia with 0.7～1.3 MAC sevoflurane is suitable for the epilepsy surgery with intraope-rative EEG monitoring, which does not influence the activity of spike bursts.

Key words: neurosurgery, epilepsy, sevoflurane, electroencephalogram