What does a low uptake in the caudate and putamen suggest in PET-FDG scans?

A low uptake of FDG (fluorodeoxyglucose) in the caudate and putamen observed in PET scans suggests neurodegenerative changes. In the context of brain metabolism, these areas are critical for various functions, including motor activity and cognition. When there is a reduced uptake of FDG in these regions, it indicates that there is diminished glucose metabolism, which is generally reflective of impaired neuronal activity and may be associated with conditions such as Parkinson's disease, Huntington's disease, or other neurodegenerative disorders.

Neurons in the caudate and putamen rely on glucose as their primary energy source, and a significant decline in FDG uptake often points to a loss of neuronal integrity or function. This may manifest early in certain neurodegenerative diseases, making changes in these regions an important factor for diagnosis and monitoring of disease progression.

In contrast, normal brain function would typically show a uniform and expected distribution of FDG uptake, and structural abnormalities would usually be assessed through different imaging modalities like MRI. Hence, the most appropriate interpretation of low FDG uptake in the caudate and putamen is that it suggests neurodegenerative changes.