In the surgery of the basilar top aneurysm, the internal carotid artery is often retracted to obtain a clear surgical field, which may lead cerebral ischemia. To prevent this the followings are noted: 1. The cross circulation especially through the anterior communicating artery is estimated before surgery, 2. The internal carotid artery is retracted at the elastic, less arteriosclerotic portion, 3. Cerebral protecting agents are administered, 4. A time keeper is arranged, 5. The duration of retraction is basically five minutes, 6. The regional cerebral blood flow and the EEG are monitored, 7. The retraction of the internal carotid artery must be extracted when there is a marked reduction of the regional cerebral blood flow, 8. The retraction of the internal carotid artery must be extracted when the slowing of the EEG is observed.
In this report, a 74-year-old female patient with a basilar top aneurysm associated with a persistent primitive hypoglossal artery is described. The surgery was performed on day 5 after subarachnoid hemorrhage through a pterional approach by retracting the internal carotid artery. A thermal diffusion flow probe was used to monitor the regional cerebral blood flow during surgery. The regional cerebral blood flow was not reduced, or was reduced little, by the retraction of the internal carotid artery, and returned to the level before retraction by the extraction in the early phase. But later, after several retractions, the reduction of the regional cerebral blood flow became rapid by the retraction, and postischemic hyperemia was observed after the extraction. In this case the reduction of the regional cerebral blood flow was not so severe (less than 50%) that the operation could be continued safely, and the aneurysm was clipped successfully. The usefulness and significance of monitoring the regional cerebral blood flow during retraction of the internal carotid artery are discussed.