What pattern of FDG uptake is characteristic for Alzheimer's Disease?

In Alzheimer's Disease, the pattern of FDG (fluorodeoxyglucose) uptake is characterized by early hypometabolism in the parietotemporal distribution. This pattern reflects the changes in brain glucose metabolism that correlate with the degenerative processes occurring in Alzheimer's.

Specifically, the parietotemporal regions are among the first to show significant metabolic decline as the disease progresses. This hypometabolic state in these areas is associated with cognitive decline, particularly in memory and language functions, which are often affected in Alzheimer’s patients. The decreased uptake of FDG in these regions can be visualized on PET scans, highlighting the areas of the brain that are not functioning optimally.

In contrast, early hypermetabolism or uniform metabolism does not align with the recognized metabolic patterns seen in Alzheimer’s. Furthermore, asymmetric hypermetabolism, particularly in the frontal lobe, typically does not characterize Alzheimer's Disease, as this condition presents distinct metabolic reductions rather than increases in metabolic activity. Thus, the identification of early hypometabolism in the parietotemporal distribution is a key marker for diagnosing and understanding the progression of Alzheimer's Disease.