Nitrous oxide: suppression of focal epileptiform activity during inhalation, and spreading of seizure activity following withdrawal.

Intraoperative brain surface electrocorticography (ECoG) is an integral part of the surgical excision of epileptogenic foci. If surgical excision is performed under general anesthesia, anesthetics should be selected that do not seriously interfere with the ECoG. We report a case where nitrous oxide appeared to suppress focal epileptiform activity at the time of intraoperative ECoG, and subsequent withdrawal of nitrous oxide produced generalized electrical seizure activity. We recommend that low concentrations of volatile anesthetics may be preferrable to nitrous oxide when ECoG is performed during epilepsy surgery in anesthetized patients.