Direct cortical EEG monitoring during temporary vascular occlusion for cerebral aneurysm surgery

Anesthetic management of cerebral aneurysm clipping includes maintenance of an acceptable transmural pressure to prevent rupture of the aneurysm, especially during surgical manipulation. Systemic hypotension has been widely practiced to achieve this goal. Recently, there has been a trend toward increasing use of temporary vascular occlusion to secure surgical control of anatomically difficult lesions, thereby avoiding systemic hypotension. Although highly desirable during vascular occlusion, monitoring of brain function with either somatosensory evoked potentials or standard scalp recording of EEG presents certain limitations during craniotomy for aneurysm clipping. We have therefore begun to use direct cortical recording using subdural strip electrodes. We report here results of cortical EEG monitoring during two cases of temporary vascular occlusion and the implications for patient management.