Reduced cerebral glucose metabolism in patients at risk for Alzheimer's disease.

While significantly reduced glucose metabolism in fronto-temporo-parietal and cingulate cortices has been demonstrated in Alzheimer's disease (AD) compared with controls, cerebral glucose metabolism in patients with mild cognitive impairment who subsequently develop AD is less well-defined. In the present study we measured cerebral glucose metabolism by positron emission tomography (PET) with (18)F-2-fluoro-2-deoxy-D-glucose in 14 patients with aging-associated cognitive decline (AACD), 44 patients with AD, and 14 healthy control subjects at baseline. The AACD patients were clinically followed up, and conversion to AD was determined. Compared with controls, AACD patients had significantly reduced glucose metabolism in the right precuneus, posterior cingulate, right angular gyrus, and bilateral middle temporal cortices, while the respective deficits were more pronounced in AD patients and also involved the frontal cortices. AACD patients who subsequently converted to AD (AACD-converters) showed more extended metabolic changes which also involved the frontal and temporal cortices, right cingulate gyrus, right thalamus, and bilateral precuneus.