Simultaneous multilobar electrocorticography (mEcoG) and scalp electroencephalography (scalp EEG) during intracranial vascular surgery: A new approach in neuromonitoring

Objective: Intraoperative neuromonitoring for intracranial vascular surgery is primarily aimed at detecting early ischemic changes to prevent subsequent infarction. Despite various neurophysiological approaches detection of early and focal ischemic changes remains difficult. This study explores the feasibility and sensitivity of intraoperative monitoring using surface EEG (scalp EEG) and multilobar Electrocorticography (mEcoG) recording during intracranial vascular procedures. Methods: About 21 recordings were acquired in 20 patients undergoing craniotomies for intracranial aneurysms (17), superficial temporalmiddle cerebral artery bypass (twice in the same patient) and arteriovenous malformation (2). The recording of scalp EEG (needle electrodes) and EcoG was performed (cupules electrodes) during all of the surgery. Signal was visually analyzed online and using spectral analysis software offline. Results: Good recordings were obtained in all cases, without adding any procedural morbidity. The most common abnormalities on mEcoG were high frequency waves (23-37 Hz; HF-beta 3), which appeared just after vascular occlusion and were occasionally followed by slow waves or burst suppression pattern. This focal pattern was seen in a majority of cases (20/21) on the mEcoG, but only in 4 out of 21 cases on the EEG. Conclusions: Multi-lobe (mEcoG) recording is feasible during cramotomies and detects earlier and more EEG pattern variation than surface EEG monitoring during intracranial vascular manipulations. The authors discuss the high sensitivity of this technique to ischemic changes. Significance: By detecting earlier and more focal changes than scalp EEG, mEcoG may favor during surgery an increase in interactive strategies and reduction of deleterious event. (c) 2005 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.