Cerebral perfusion and glucose metabolism in Alzheimer's disease and frontotemporal dementia: two sides of the same coin?

Alzheimer's disease (AD) and frontotemporal (FTD) dementia can be differentiated using [F-18]-2-deoxy-2-fluoro-D-glucose (FDG)-PET. Since cerebral blood flow (CBF) is related to glucose metabolism, our aim was to investigate the extent of overlap of abnormalities between AD and FTD. Normalized FDG-PET and arterial spin labelling (ASL-MRI)-derived CBF was measured in 18 AD patients (age, 64 +/- 8), 12 FTD patients (age, 61 +/- 8), and 10 controls (age, 56 +/- 10). Voxel-wise comparisons, region-of-interest (ROI), correlation, and ROC curve analyses were performed. Voxel-wise comparisons showed decreased CBF and FDG uptake in AD compared with controls and FTD in both precuneus and inferior parietal lobule (IPL). Compared with controls and AD, FTD patients showed both hypometabolism and hypoperfusion in medial prefrontal cortex (mPFC). ASL and FDG were related in precuneus (r = 0.62, p <0.001), IPL (r = 0.61, p <0.001), and mPFC across groups (r = 0.74, p <001). ROC analyses indicated comparable performance of perfusion and metabolism in the precuneus (AUC, 0.72 and 0.74), IPL (0.85 and 0.94) for AD relative to FTD, and in the mPFC in FTD relative to AD (both 0.68). Similar patterns of hypoperfusion and hypometabolism were observed in regions typically associated with AD and FTD, suggesting that ASL-MRI provides information comparable to FDG-PET. Similar patterns of hypoperfusion and hypometabolism were observed in patients with dementia. For both imaging modalities, parietal abnormalities were found in Alzheimer's disease. For both imaging modalities, prefrontal abnormalities were found in frontotemporal dementia