[Studies of cerebral blood flow and metabolism in patients with senile dementia of the Alzheimer's type and diagnostic evaluation of the dementing illnesses by positron emission tomography].

This study was designed to estimate cerebral dysfunction in senile dementia of the Alzheimer's type (SDAT). Regional cerebral blood flow (rCBF), oxygen extraction fraction (rOEF) and cerebral oxygen consumption (rCMRO2) were studied in 16 patients with SDAT and 5 age-matched normal elderly people by positron emission tomography (PET), using the 15O labeled CO2 and O2 inhalation technique. This technique was also applied to the evaluation of PET in diagnosing the dementing illnesses. In this study, a total of 19 pairs of bilateral cerebral regions were analyzed and the reductions of rCBF and rCMRO2 in each region were compared with those of the primary sensorimotor cortex to demonstrate any significant localized difference between each clinical stage of the SDAT and normal controls. In the mild SDAT group, CMRO2 of the temporal cortex was significantly reduced, as compared with that of controls. In the moderate SDAT group, CBF of the temporal cortex and CMRO2 of the temporal and parietal cortices were significantly reduced. In the severe SDAT group, CBF and CMRO2 of the frontal cortex were also reduced and those of the occipital cortex were relatively unchanged. This suggested that mildly demented patients showed a metabolic reduction in the temporal cortex and as the dementia progressed, metabolic reductions were extended to the parietal and frontal cortices. Reductions in blood flow were followed by further metabolic reductions. More detailed investigation of the PET images of SDAT revealed that relative oxygen hypometabolism of the posterior temporal and posterior parietal association cortices occurred in the mildly demented patients earlier than that of the other association cortices. These findings are consistent with neuropathological studies of SDAT. The right/left ratio of rCMRO2 was also analyzed in each region. The right/left oxygen metabolic asymmetry in the temporal and parietal cortices was correlated with the difference between speech and visuospatial functions. Namely, the patients with a lower metabolism in the left hemisphere had more disturbances in speech than visuospatial functions. In addition, the PET images of SDAT were compared with those of multi-infarct dementia (MID) and Pick disease. In patients with MID, there were reductions of CBF and CMRO2 unhomogenously all over association cortices, but the reductions were most remarkable in the frontal cortex. Patients with Pick disease showed diffuse lobar reductions of CBF and CMRO2 in the frontal and temporal cortices.(ABSTRACT TRUNCATED AT 400 WORDS)