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.

Abstract

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 (rCMR02) were studied in 16 patients with SDAT and 5 age-matched normal elderly people by positron emission tomography (PET), using the 150 labeled CO2 and 02 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 rCMR02 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, CMR02 of the temporal cortex was significantly reduced, as compared with that of controls. In the moderate SDAT group, CBF of the temporal cortex and CMR02 of the temporal and parietal cortices were significantly reduced. In the severe SDAT group, CBF and CMR02 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 rCMR02 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 CMR02 unhomogeneously 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 CMR02 in the frontal and temporal cortices. These findings of MID and Pick disease were clearly different from those of SDAT, so PET will provide a sensitive means to differentiate among the dementing illnesses.These results suggest that PET using the 150 steady state technique is sensitive in detecting abnormalities of rCBF and rCMRO, of SDAT and useful for estimating cerebral dysfunction in SDAT, Key words: senile dementia of the Alzheimer's type, positron emission tomography, cerebral blood flow, cerebral oxygen metabolism, dementing illnessCorrespondence to Shizuki Sakam...

Imaging the Earliest Stages of Alzheimers Disease

“…Paralleling the pattern of decrease glucose uptake, PET studies have observed a decrease in H 2 15 O, and therefore CBF, in the temporal and parietal cortices [58][59][60]. Although a few studies show areas of increased perfusion in early AD, mostly in the primary cortex and dorsolateral frontal region, Fig.…”

Frontotemporal Dementia Can Be Distinguished from Alzheimer’s Disease and Subcortical White Matter Dementia by an Anterior-to-Posterior rCBF-SPET Ratio

“…Therefore, this ratio is suggested to be of benefit in differential diagnosis. The ratio reflects a hypofrontal flow pattern in FTD, which has been described in previous studies [12][13][14][15][16][17]41]. However, fewer patients were included in these studies and other methods were sometimes used, e.g.…”

“…Among the methods for semiquantification, the min-max method has been reported to involve a smaller observer error and to have bet- ter reproducibility than other more commonly used methods [11]. Investigations of rCBF in FTD, using different methods, have generally found reductions in the frontal lobes [12][13][14][15][16][17]. Such reductions are included in the proposed Lund-Manchester consensus criteria for a diagnosis of FTD [18].…”

“…Biparietotemporal hypoperfusion has been found to be a marker of AD [15,16,20,21], with high sensitivity but moderate specificity [16]. In VAD, which most often has been regarded as synonymous with multi-infarct dementia, multiple spotty often asymmetrical focal pathologies have been described [12,22], whereas the rCBF pattern of SWD is less known. CT and magnetic resonance imaging (MRI) are structural brain imaging methods, which are also used in differential diagnosis to exclude disorders like VAD.…”

Cerebromicrovascular Pathology in Alzheimer’s Disease Compared to Normal Aging

“…This observation which has been widely referenced, was recently chal lenged by more sensitive PET studies which have shown that patients with Alzheimer's disease have significant increases in OEF [83,84]. Moreover, misery perfusion appears present not only in Alzheimer patients but also in other dementias [85], In one clinical case study, neurofibrillary tangles were re ported to form quickly in the nucleus basalis of Meynert following a cerebral infarction near the area of tangle accumulation [86],…”