Primary cerebral blood flow deficiency and Alzheimer's disease: shadows and lights.

Alzheimer's disease (AD) is a degenerative disorder characterized by a decreased regional cerebral blood flow (CBF). It is most likely that a reduction in CBF could displace a pathway leading to AD genesis, in so far neuron death explains a sustained reduction in the supply of oxygen, glucose, and nutrients. Nevertheless, the concept of secondary CBF deficiency cannot explain the critical stages of early memory loss while, on the other hand, the picture of progressive ischemia due to primary CBF decline sheds light on the course of AD in a most persuasive manner. The concept of primary CBF deficiency is even more strengthened by the lack of correlation between degree of dementia and amount of CBF. Vascular abnormalities, frequently observed to co-occur with AD, might play a critical role in the initiation and aggravation of AD pathology given that the elimination of amyloid-β (Aβ) through a vascular route is an important brain Aβ clearance mechanism and its failure leads to formation of vascular amyloidosis and dense-core plaques. The goal of this review is to provide scientists comprehensive knowledge of the state-of the art influence vascular damage and reduced perfusion have on the final development of AD and to hopefully stimulate more research in this area of neuroscience.