This discrepancy in hypoperfusion may also explain why CBF changes in FTD patients were limited to the ACC. Additional hypoperfusion in FTD has been reported in the temporal lobe, medial PFC, and thalamus [29], whereas hypometabolism on PET is generally limited to frontal regions in early-stage fluent PPA and behavioral-variant FTD (bv-FTD) [33]. The localized ACC hypoperfusion may, thus, be due to the disease still being at an early stage. Furthermore, focal ACC neuronal loss has been associated with tau pathology [34] which is correlated with both bv-FTD and PPA variants [35], suggesting our FTD sample comprises predominantly patients with tau pathology.