Figure 3.

Theoretical cascade of events leading to cognitive failure and Alzheimer or vascular dementia. The cascade may begin with a double drop in cerebral blood flow (see Figure 2) during normal aging and in the presence of vascular risk factors. These 2 events are reported to alter brain hemodynamics giving rise to chronic cerebral hypoperfusion. With time, critically attained threshold of cerebral hypoperfusion (CATCH) is reached where brain cells, especially those sensitive to ischemia in the inferior temporal region, precuneus, and posterior cingulate cortex can no longer cope with reduced energy substrate delivery. The outcome of this process affects executive function, verbal fluency, psychomotor speed, and mental flexibility, which may progress to mild cognitive impairment, severe neurodegeneration, and dementia.