Hospital between 1982 and 1995, underwent balloon Matas tests (BMT) , measurement of mean stump pressure (MSP) and mean arterial blood pressure (MABP). Eleven of these patients had carotid aneurysms and 1 had a vertebral aneurysm . Two patients, whose MSPs were under 50 mmHg , did not tolerate BMT and 10 patients tolerated BMT . Six patients finally underwent proximal occlusion of the parent artery, and their postoperative course was observed . The mean follow-up period was 4 years (range 2

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... hs to 12 years) . One of the patients, who did not tolerate BMT (MSP was 49 mmHg) received STA-MCA anastomosis before proximal occlusion of the parent artery , and he did not suffer from any delayed ischemic complication after the occlusion. Another patient who tolerated BMT suffered from a cerebral infarction 4 days after the occlusion due to thrombosis of the perforating artery near the aneurysm , but she did not suffer from any delayed ischemic complication of the cortical branch . The other patients did not suffer from any ischemic complication and their aneurysms were thrombosed and absorbed . Delayed ischemic complications can occur after proximal occlusion of the parent artery for unruptured giant aneurysms, although the patient may have tolerated BMT . The measurement of MSP and cerebral blood flow (CBF) by Xe-CT or SPECT during BMT have been accepted methods to predict delayed ischemic complications. Xe-CT during BMT is less practical because it requires moving a patient from the angiography room to the CT room . CBF values that can be measured by SPECT are not an absolute but a relative value . It is considered that delayed ischemic complications rarely occur when the MSP is over 50 mmHg . The measurement of MSP during BMT, although not a new method , is simple and practical. In conclusion, the measurement of MSP during BMT is very useful to decide if arterial reconstruction is indicated before proximal occlusion of the parent artery and to predict delayed ischemia of the cortical branch. Occurrence of delayed ischemic complications will be rare if troubles can be avoided during the aneurysm-thrombosing process.