Clinical Study Of Simultaneous Cortical EEG And Scalp EEG Monitoring During Anterior Circulation Aneurysm Surgery

Objective To explore a simple and effective method for intraoperative monitoring of cortical ischemia after temporary vessel occlusion during anterior circulation aneurysm surgery. To explore the effect of combination of cortical electroencephalography (EEG) and scalp EEG monitoring on surgical strategy and patients'postoperative representations in anterior circulation aneurysm surgery. To define the safe time limit for temporary vascular occlusion during anterior circulation aneurysm surgery with monitoring of cortical and scalp electroencephalography (EEG).Method From Apr. To Nov. 2008, a cohort of 58 anterior circulation aneurysms of 52 patients underwent aneurysm surgery was monitored prospectively with simultaneous cortical electroencephalography (EEG) and scalp EEG.Cortical EEG was used for monitoring of potential cortical ischemia and scalp EEG for depth of anesthesia. According to the international 10-20 Electrode Placement System, scalp electrodes were placed on O1, O2, P3, P4, T5, T6. Cortical stripe electrode was placed on the surface of cortex territory supplied by the artery which may suffer temporary occlusion. Cortical EEG and scalp EEG data were comparatively analyzed online and offline with the patients'postoperative representations and surgical strategies which were affected by changes of EEG data were analyzed. The time of temporary arterial occlusion during aneurysm surgery and the postoperative procedure related ischemic events in relation to changes of cortical EEG were studied.Results Temporary vascular occlusion was performed in 41 major arteries of 40(40/58) aneurysms. Among these cases, cortical EEG waveform changed significantly in 19(19/41) arteries of 18 patients, meanwhile, scalp EEG not. Only 9(9/18) patients with cortical EEG significant change developed postoperatively temporary occlusion related ischemic event and 5 cases developed permanent neurological deficit. None procedure-related ischemic event was seen in patients either without temporary occlusion or without cortical EEG significant change. As anesthesia deepens, both cortical EEG and scalp EEG change similarly. According to EEG data, 19 operational strategies changed, which included changing type of revascularization in 1 case, precautious bone decompression in 2, sacrificing parent artery in 2, fast clipping aneurysm neck in 7, and intermittent reperfusion in 7. One patients underwent postoperative second operation because of not understanding the cortical EEG significant changes. Cortical EEG can change dramatically in different major artery when it was intentionally occluded. When cortical EEG changes indicate serious ischemia, patients which vessels were occluded for less than 10 minutes had not postoperative procedure related ischemic complication.Conclusions Combination of cortical EEG and scalp EEG monitoring for potential ischemia and deep of anesthesia respectively during anterior circulation aneurysm surgery is a feasible and effective method to detect real time cerebral cortical ischemia and to identify influence of anesthetic agents. simultaneous cortical EEG and scalp EEG monitoring can real-time provide information of focal cortical blood flow for operators. Applying these technique of monitoring and emphasizing changes of EEG can help guide therapeutic decisions and may reduce temporary occlusion related ischemic complication. Moreover, it can avoid unnecessary revascularization or unfavorable second operation etc. When cortical EEG changed dramatically, 10 minutes may be the longest permissible time of temporary clamping of the cerebral artery without postoperative procedure related complications. As far as each individual is concerned, the ability of major cerebral arteries to tolerate temporary occlusion may be not different.