[Cerebral hemodynamics in patients with dementia]

Cerebral blood flow (CBF) at rest was measured by 123I-IMP SPECT and the standing test was conducted by 99mTc-HMPAO SEPCT in patients with dementia of Alzheimer's type (DAT) and vascular dementia (VD) in order to evaluate cerebral autoregulation and to consider the diagnostic significance of this determination and test. CBF at rest decreased significantly in all regions in the DAT and VD groups compared to the control groups (healthy aged persons, group C). The value of mean CBF also decreased significantly in the DAT (40.1 micromilligrams/100 g/min) and VD groups (41.3) as compared to group C (51.0). In the DAT groups, the CBF was significantly lower in the parietal region compared to VD groups, and CBF and Hasegawa's dementia score showed a positive correlation in the temporal and parietal regions. Decreases in blood pressure upon standing were about 10 mmHg in all three groups, but the decrease rate in mean CBF was significantly greater in the VD groups (20.2%) than in the C (5.0%) and DAT groups (4.0%). The dysautoregulation index (D.I. delta; % CBF mmHg), used as a measurement of cerebral autoregulation, was significantly higher in the VD groups (1.7) than in the C(0.5) and DAT groups (0.3). This index made it possible to make differential diagnosis in some patients in whom it was impossible using CBF at rest, probably due to impaired cerebral autoregulation and atherosclerotic changes in VD patients. Our findings suggest that D.I. provides information on the condition of patients that cannot be obtained with CBF at rest and assists in differential diagnosis.