Specific response of the epileptic focus to anesthesia with propofol

Twenty patients suffering from medically intractable epilepsy were submitted to invasive presurgical evaluation using subdural strip electrodes for chronic electrocorticographic (ECoG) recordings. A short anesthesia of 12–15 min was induced to ensure painless percutaneous removal of the subdural electrode strips. Anesthesia was provided by two consecutive intravenous injections of propofol (50 and 70 mg or 70 and 140 mg) preceded by fentanyl (0.1–0.15 mg) in 12 patients. In order to test whether the epileptic focus showed a specific response following application of propofol, the first 12 min of ECoG recordings, prior to removal of the subdural strip electrodes, were visually analyzed. Specific patterns of response confined to the epileptic focus (foci) were observed in 18 of 20 patients following application of at least one of the two doses of propofol. Patterns observed in the epileptogenic area consisted of (a) a loss or marked reduction of activity induced by propofol (n = 16), (b) a maximum of suppression of brain activity (n = 12), (c) suppression of spontaneous interictal activity (n = 10), (d) induction of epileptiform activity (n = 5), and (e) induction of a habitual seizure (n = 1). In summary, ECoG recordings during anesthesia with propofol provide complementary information about the epileptic focus in the process of presurgical evaluation of epileptics.