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STA-MCA anastomosis and collateral circulation.

Two representative cases of anastomosis of the superficial temporary artery (STA) to the middle cerebral artery (MCA) for the treatment of focal cerebral ischemia are presented and the changes in collateral circulation following the surgery are discussed based on twenty cases treated in this way. Redistribution of cerebral circulation took place following the surgery. Although the collateral pathway constructed microsurgically was narrow and slender in the early postoperative period, it dilated with time in a majority of the cases. On the other hand, some of preexisting extra to intracranial collateral channels atrophied and narrowed following the surgery. The role of the microsurgically constructed bypass might be of limited value in the early postoperative period. Spontaneously developed collateral channels must, therefore, be preserved to operate safely for prevention of cerebral ischemic attacks particularly in this period. Our findings indicate that sacrificing the anterior branch of the STA for STA-MCA anastomosis might be risky in certain cases in which the anterior branch was function ing as one of the main preexisting extra to intracranial collateral routes. In such cases only the posterior branch of STA should be used as a donor artery.