Brain metabolic maps in Mild Cognitive Impairment predict heterogeneity of progression to dementia

[F-18]FDG-PET imaging has been recognized as a crucial diagnostic marker in Mild Cognitive Impairment (MCI), supporting the presence or the exclusion of Alzheimer's Disease (AD) pathology. A clinical heterogeneity, however, underlies MCI definition. In this study, we aimed to evaluate the predictive role of single -subject voxelbased maps of [F-18]FDG distribution generated through statistical parametric mapping (SPM) in the progression to different dementia subtypes in a sample of 45 MCI. Their scans were compared to a large normal reference dataset developed and validated for comparison at single -subject level. Additionally, A beta 42 and Tau CSF values were available in 34 MCI subjects. Clinical follow-up (mean 28.5 +/- 7.8 months) assessed subsequent progression to AD or non -AD dementias. The SPM analysis showed: 1) normal brain metabolism in 14 MCI cases, none of them progressing to dementia; 2) the typical temporo-parietal pattern suggestive for prodromal AD in 15 cases 11 of them progressing to AD; 3) brain hypometabolism suggestive of frontotemporal lobar degeneration (FTLD) subtypes in 7 and dementia with Lewy bodies (DLB) in 2 subjects (all fulfilled HID or DLB clinical criteria at follow-up); and 4) 7 MCI cases showed a selective unilateral or bilateral temporo-medial hypometabolism without the typical AD pattern, and they all remained stable. In our sample, objective voxel-based analysis of [F-18]FDG-PET scans showed high predictive prognostic value, by identifying either normal brain metabolism or hypometabolic patterns suggestive of different underlying pathologies, as confirmed by progression at followup. These data support the potential usefulness of this SPM [F-18]FDG PET analysis in the early dementia diagnosis and for improving subject selection in clinical trials based on MCI definition. (C) 2014 Published by Elsevier Inc