Hemodynamic aspects of Alzheimer's disease.
Neuroradiological functional imaging techniques demonstrate the patterns of hypoperfusion and hypometabolism that are thought to be useful in the differential diagnosis of Alzheimer's disease (AD) from other dementing disorders. Besides the distribution patterns of perfusion or energy metabolism, vascular transit time (VTT), vascular reactivity (VR), and oxygen extraction fraction (OEF), which can be measured with positron emission tomography (PET), provide hemodynamic aspects of brain pathophysiology. In order to evaluate the hemodynamic features of AD, PET studies were carried out in 20 patients with probable AD and 20 patients with vascular dementia (VaD). The PET findings were not included in their diagnostic process of AD. Using oxygen-15-labeled compounds, cerebral blood flow (CBF), cerebral metabolic rate of oxygen (CMRO(2)), OEF, cerebral blood volume, and VTT were measured quantitatively during resting state. To evaluate VR, CBF was also measured during CO(2) inhalation. There was a significant increase in OEF in and around the parietotemporal cortices, but both VTT and VR were well preserved in patients with AD. By contrast, VR was markedly depressed and VTT was mildly prolonged in patients with VaD. Thus, from the hemodynamic point of view, the preservation of vascular reserve may be a distinct difference between AD and VaD. Furthermore, this indicates a hemodynamic integrity of the vasculature in the level of arterioles in AD.
Nagata
Ken
K
Department of Neurology, Research Institute for Brain and Blood Vessels, 6-10 Senshu-Kubota-Machi, Akita 010-0874, Japan. nagata@akita-noken.go.jp
Sato
Mika
M
Satoh
Yuichi
Y
Watahiki
Yasuhito
Y
Kondoh
Yasushi
Y
Sugawara
Maki
M
Box
Georgia
G
Wright
David
D
Leung
Sumie
S
Yuya
Hiromichi
H
Shimosegawa
Eku
E
D000368:Aged; D000544:Alzheimer Disease / Q000000981:diagnostic imaging / Q000503:physiopathology*; D000818:Animals; D001921:Brain / Q000098:blood supply / Q000000981:diagnostic imaging / Q000473:pathology; D002560:Cerebrovascular Circulation; D015140:Dementia, Vascular / Q000503:physiopathology*; D004734:Energy Metabolism; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D008875:Middle Aged; D008954:Models, Biological; D014055:Tomography, Emission-Computed