Improvement of cerebral blood flow and/or CO2 reactivity after superficial temporal artery-middle cerebral artery bypass in patients with transient ischemic attacks and watershed-zone infarctions

The effect of extracranial-intracranial bypass anastomosis on cerebral blood flow and CO₂ reactivity during hypocapnia was investigated in ten patients with transient ischemic attacks or watershed infarctions due to carotid occlusive diseases. Six patients had occlusion and four had stenosis (>50%) of the internal carotid artery. Those with infarctions had increased cerebral blood flow and CO₂ reactivity postoperatively, and improved clinically. Those with transient ischemic attacks due to stenosis (>50%) of the internal carotid artery had increased CO₂ reactivity postoperatively but constant normal regional blood flow. Cerebral blood flow improved in those with poorer flow, CO₂ reactivity increased in those with better reactivity, and better CO₂ reactivity preoperatively brought about a greater flow increase. The pre- and postoperative evaluation of cerebral blood flow and CO₂ reactivity is believed to be useful in evaluating the effectiveness of bypass anastomosis. Preoperative evaluation might be informative in selecting candidates for bypass.