Cerebral blood flow (CBF) and cerebrovascular reserve capacity (CRC) were measured by stable xenon computerized tomography (Xe-CT) and acetazolamide test in 22 patients with cerebrovascular disease before and after extracranial-intracranial (EC-IC) bypass surgery for minor stroke, reversible ischemic neurological deficit, or transient ischemic attack. All patients had occlusive lesions of the major arterial trunk that was shown angiographically. The patients were divided into four groups

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... ng to the preoperative resting rCBF and rCRC. All 4 patients with normal resting rCBF and normal rCRC (Group I) showed no postoperative improvement of both parameters. All 3 patients with normal resting rCBF and reduced rCRC (Group II) showed postoperative improvement of rCRC. One of 4 patients with reduced rCBF and normal rCRC (Group III) showed an increase in rCBF and 2 in rCRC. Of 11 patients with reduced rCBF and reduced rCRC (Group IV), 5 had postoperative increase in resting rCBF and 9 had increased rCRC. These results suggest that in the preoperative state, Group I has normal hemodynamics and Group II has preserved normal rCBF with vasodilatation. Group III has matched low perfusion without vasodilatation. Group IV has two types of hemodynamic states, i,e, one is a state of misery perfusion and the other is a state of matched low perfusion with vasodilatation.