ABSTRACT

Objective

To use digital histology in a large autopsy cohort of Lewy Body Disorder (LBD) patients with dementia to test the hypotheses that co‐occurring Alzheimer’s disease (AD) pathology impacts the anatomic distribution of α‐synuclein (SYN) pathology and that co‐occurring neocortical tau pathology in LBD associates with worse cognitive performance and occurs in a pattern differing from AD.

Methods

Fifty‐five autopsy‐confirmed LBD (PDD: 36, DLB:19) patients and 25 AD patients were studied. LBD patients were categorized as having moderate/severe AD co‐pathology (SYN+AD=20) or little/no AD co‐pathology (SYN‐AD=35). Digital measures of tau, Aβ, and SYN histopathology in neocortical and subcortical/limbic regions were compared between groups and related to antemortem cognitive testing.

Results

SYN burden was higher in SYN+AD than SYN‐AD in each neocortical region (F(1,54)=5.6‐6.0,p<0.02) but was equivalent in entorhinal cortex and putamen (F(1,43‐49)=0.7‐1.7,p>0.2). SYN+AD performed worse than SYN‐AD on a temporal‐lobe mediated naming task (t(27)=2.1,p=0.04). Antemortem cognitive test scores inversely correlated with tau burden (r=‐0.39 to ‐0.68,p<0.05). AD had higher tau than SYN+AD in all regions (F(1,43)=12.8‐97.2,p<.001); however, SYN+AD had a greater proportion of tau in the temporal neocortex than AD, (t(41)=2.0,p<.05) whereas AD had a greater proportion of tau in the frontal neocortex than SYN+AD (t(41)=3.3,p<0.002). SYN+AD had similar severity and distribution of neocortical Aβ compared to AD (F(1,40‐43)=1.6‐2.0,p>.1).

Interpretation

LBD patients with AD co‐pathology harbor greater neocortical SYN pathology. Regional tau pathology relates to cognitive performance in LBD dementia, and its distribution may diverge from pure AD. Tau co‐pathology contributes uniquely to the heterogeneity of cognitive impairment in LBD.

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