Multiple focal cortical and subcortical defects on an FDG study are indicative of which diagnosis?

Multiple focal cortical and subcortical defects observed on an FDG (fluorodeoxyglucose) PET study are indicative of vascular dementia. This condition results from impaired blood flow to the brain due to vascular issues, such as stroke or chronic ischemia. FDG PET imaging highlights areas of altered glucose metabolism, which commonly correlates with the regions of the brain affected by insufficient blood supply in vascular dementia.

In patients with vascular dementia, the PET scan often reveals areas of hypometabolism in both cortical and subcortical regions, providing evidence of the impact of vascular pathology on cognitive function. This characteristic pattern can help differentiate vascular dementia from other types of dementia, where the patterns of metabolic activity may vary significantly.

It's important to note that Alzheimer's Disease typically shows more diffuse patterns of cortical hypometabolism, primarily in the parietal and temporal lobes, and Frontotemporal Dementia often shows localized areas of hypometabolism that can differ based on the variant. Parkinson's Disease may present with less prominent focal defects on FDG PET. Understanding these distinctions is critical for accurate diagnosis and appropriate management.