Value of 18F-FDG PET in differentiating Alzheimer's disease with frontotemporal dementia

Objective To delineate the pattern of reduction of cerebral glucose metabolism in patients with Alzheimer's disease (AD) and frontotemporal dementia (FTD) and investigate the value of 18F-FDG PET in the differential diagnosis. Methods Twenty patients with FTD (behavioral variant) and 20 AD patients underwent 18F-FDG PET scanning. All the images were compared with that from 20 healthy age-matched control subjects on a voxel-based analysis (VBA) using SPM5. Visual analyses of 18F-FDG PET were performed by 2 independent nuclear medicine specialists who were blinded to the clinical background. Results 1) The PET scans of all the patients in 2 groups presented impairment of cortical metabolism. 2) Subjects with AD showed hypometabolism in the bilateral temporoparietal association cortex and posterior cingulate cortex, and hypometabolim in part of bilateral frontal lobes was observed in patients with progression. The metabolic activity was relatively kept in the primary motor-sensor cortex, occipital lobes and subcortical structures (basal ganglia and thalamus). The asymmetric hemispheric hypometabolic involvement was rare and observed in only 2 of 20 cases. 3) Subjects with FTD showed a significant hypometabolism of the frontal lobes and anterior temporal lobes, accompanied by mild to moderate reductions in glucose metabolism in parietal cortices and subcortical structures. The asymmetric hemispheric hypometabolic involvement was commonly observed in 16 of 20 cases with right-dominant type in 4 of 16 cases and left-dominant type in 12 cases. Conclusions 18F-FDG PET is a reliable diagnostic test in distinguishing FTD from AD due to the sharp contrast pattern of cerebral glucose hypometabolism. doi: 10.3969/j.issn.1672-6731.2014.03.012