Positron emission tomography in normal aging and Alzheimer's disease

Age differences are not found for the regional cerebral metabolic rate for glucose (rCMR glc) measured with positron emission tomography (PET) with 18F-2-deoxy-D-glucose, in healthy subjects at rest and with reduced sensory stimulation. Furthermore, measures of cognitive function are not correlated with resting rCMR glc in healthy subjects. In patients with presumptive Alzheimer's disease (AD), regional cerebral blood flow is reduced throughout the brain in relation to the severity of dementia, whereas regional reductions in rCMR glc are correlated with neuropsychometric deficits subserved by those regions. Right-left asymmetries in rCMR glc appear early in AD and are correlated with appropriate right-left asymmetries in language as compared to visuo-constructive abilities. Thus, PET, when combined with neuropsychological measures, can be used to examine specific cerebral function changes during the course of AD.