Superficial temporal-middle cerebral artery bypass. A detailed analysis of multiple pre- and postoperative angiograms in 40 consecutive patients.

Pre- and postoperative angiograms on 40 patients undergoing superficial temporal-middle cerebral artery (STA-MCA) bypass surgery have been examined in detail. Multiple postoperative angiograms have been obtained to evaluate the change in both the bypass circuit and the intracranial circulation over time. A reproducible system for evaluating the degree of intracranial vascular filling via the bypass is introduced. The study shows that the STA and its anastomotic branch increase in size over time, measured in months, in the majority of patients. This is paralleled by a progressive increase in the degree of intracranial vascular filling. These changes are proportional to the severity of the vascular disease before surgery. The pattern of preoperative collateral circulation may change over time following the addition of the bypass circuit. The progressive change over time suggests that a static analysis at one time may belie the true effect of the surgery. The change of collateral circulation with augmentation of blood supply to areas of the brain other than those affected by the recent ischemic event, means that a total cerebral evaluation including neuropsychological testing may be necessary for adequate evaluation of the effect of the bypass surgery.