Cerebral metabolism as measured with positron emission tomography (PET) and [18F] 2-deoxy-D-glucose: healthy aging, Alzheimer's disease and Down syndrome.

Brain metabolism has been measured with positron emission tomography and 18[F] fluoro-2-deoxyglucose. Brain metabolic function remains age invariant in healthy aged subjects 21 to 83 years. Brain metabolism remains unchanged in the mild-moderate severity Alzheimer's disease group and significantly reduced throughout the brain in the late-severe form. Serial assessments over 2 1/2 years of brain metabolic function in an Alzheimer's disease subject with positron emission tomography and 18[F]-fluoro-2-deoxyglucose revealed initial reductions in the parietal lobe and regions prior to neuropsychological changes. Marked elevations in brain metabolism were found in young adult Down syndrome subjects while age-related declines were found in the middle aged (non-demented) Down syndrome subjects and further reductions in the demented Down syndrome individuals.