PATHOLOGIC ASSOCIATIONS OF FDG PET IN LEWY BODY DISEASE

Abstract

Among individuals with Lewy body disease (LBD), pathologic correlates of clinical course include the presence and extent of coexisting Alzheimer's pathology and the presence of transitional or diffuse LBD. The objective of this study was to determine whether 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) signatures of LBD would be associated with these pathologies. 36 participants with pathologically-confirmed LBD who underwent antemortem FDG-PET were included in this study. We evaluated whether FDG-PET features of DLB, including the cingulate island sign (CIS) and occipital hypometabolism, varied by Lewy body stage (amygdala only, transitional, diffuse) and Braak neurofibrillary tangle stage. We performed a recursive partitioning tree algorithm to classify our subjects into distinctive sub-groups. The median imaging age was 73 and 75% were male. The median age at death was 75.5. 26 participants had diffuse LBD, 8 participants had transitional LBD, and 2 had amygdala only LBD. There was no difference in CIS or occipital hypometabolism by LBD type (transitional, diffuse). In contrast, those with a lower Braak stage (I-III) had a higher CIS compared to those with a higher Braak stage (IV-VI). For the CIS, there were 3 distinct groups based on the partitioning analysis (Braak I-II), (Braak III-IV) and Braak (V-VI). The partitioning found two groups for occipital hypometabolism (Braak I-III and Braak IV-VI). Among pathologically confirmed LBD patients, FDG-PET features varied by Braak neurofibrillary tangle stage, but not LBD subtype. Predicting the extent of AD pathology antemortem may allow for improved prognostication of the clinical course of patients with LBD.