Monitoring of direct cortical responses during temporary arterial occlusion at aneurysm surgery.

Direct cortical response (DCR) of the cerebral cortex was monitored during temporary occlusion of the feeding artery to a cerebral aneurysm in 24 patients. Animal experiments had shown that this response can be used as an index of the depth of ischaemia. In all 8 patients with middle cerebral artery occlusion and 3 out of 4 patients of bilateral A1 occlusion, the amplitude of DCR decreased, and two of them showed complete disappearance of DCR. In 10 patients with common carotid artery occlusion, only one patient showed amplitude decrease of DCR to half. These results might indicate the difference of collateral circulatory flow in each individual case. The authors suggest monitoring of DCR in temporal occlusion to be a most important practical method for ascertaining the maximal duration of temporary occlusion possible without causing infarction.