Intraoperative electrocorticography: variants of periodic patterns in the structural epilepsy

Abstract

The results of intraoperative electrocorticography for patients with the structural epilepsy are influenced by two main factors: the action of general anesthetic and the mechanisms of epileptogenesis. Under the general anesthesia, there is a dose-dependent suppression of the bioelectrical activity of the brain; you could even register the outburst-diminution and outburst-suppression types of the periodic patterns. The study was carried out to classify the variants of periodic activity registered on the intraoperative electrocorticogram for patients with a structural epilepsy. The work was carried out during the examination and surgical treatment of the two groups of patients: 1) 19 patients (men/women 10/9, 1945 years old) with focal drug-resistant epilepsy; 2) 19 patients (men/women 8/11, 2868 years old) with structural epilepsy associated with the intracerebral tumors. All patients underwent surgical removal of the epileptic focus under a neurophysiological control. Surgical interventions were performed under the sevoflurane-based inhalation anesthesia in doses from 1.01.5 MAC (minimum alveolar concentration). Periodic activity on intraoperative electrocorticography was represented with the outburst-suppression type of patterns and patterns containing epileptiform discharge graph elements: discharge- postdischarge depression, outburst-suppression with discharges against the background of depression, small electrical elements with epileptiform discharges. The presence of discharge graph elements in the periodic patterns has a neurophysiological correlation with a drug-resistance in the structural epilepsy.