Studies on cerebral hemodynamics by single photon emission computerized tomography, 2

Cerebral blood flow (CBF) was measured by using Xe-133 inhalation method before and after administration of Diamox (DM) to evaluate the hemodynamics in a total of 34 patietns with cerebrovascular occlusive disease. Hemodynamic changes after bypass surgery were also evaluated. According to CBF findings and DM reactivity, the patients were divided into 4 types: (1) normal findings in both CBF and DM reactivity, suggesting well-developed collateral circulation and normal cerebral perfusion pressure (CPP), (2) decrease in CBF, probably due to reduction in the metabolic demand, and normal DM reactivity, (3) normal CBF and decreased DM reactivity, suggesting moderate vasodilation due to reduced CPP, and (4) decreased CBF and impaired DM reactivity. One patient in the group of type 1 had transient hemiplegia after administration of DM. Retrograde ophthalmic flow or collateral flow via leptomeningeal anastomosis on angiograms was frequently associated with impairment of DM reactivity, suggesting reduction of CPP. CBF on the operation side was increased by bypass surgery. Most of the patients recovered from impaired DM reactivity after surgery. Of 13 patients having impaired DM reactivity, 9 had obviously increased cerebral blood volume (CBV) on the occluded side compared with the non-occluded side. In the remaining 4 patients, CBV did not increase on the occluded side. Impaired DM reactivity may not necessarily be caused by the compensative increase in CBV, i.e. vasodilation, due to reduced CPP. (N.K.) 57 refs