gms | German Medical Science

Introduction: The ageing brain is characterized by the presence of multiple pathologies and cases that neuropathologically fulfill criteria for both Alzheimer's disease (AD, e.g., NIA-AA criteria: High AD Neuropathologic Change) and Dementia with Lewy bodies (DLB; e.g., McKeith neocortical Lewy body disease) may be classified as mixed dementia: AD and DLB (mixed AD/DLB). Here, we compare mixed AD/DLB cases that clinically presented as either AD or DLB.

Methods: We investigated eight cases (75% female; mean age 74.5±3.4 yrs) that neuropathologically fulfilled the criteria for both AD and DLB. Clinically, four cases each were diagnosed as either AD or DLB. Tau, amyloid-β (Aβ) and α-synuclein (α-syn) pathologies were assessed semiquantitatively according to standardized criteria on 4 (Tau, Aβ) and 5 tiered (α-syn) scales in neocortical, limbic and brainstem regions.

Results: Tau pathology was severe in all regions, except for one case that showed only moderate neocortical tau pathology and was clinically diagnosed as AD. The severity of both α-syn and Aβ pathology varied between cases but no significant differences were seen between clincial AD and DLB cases.

Discussion: Using semiquantitative methods we could not find significant differences in the amount of neuropathological hallmark lesions between clinical AD and DLB cases that neuropathologically fulfilled the criteria for both AD and DLB. Our findings suggest that a more quantitative approach is warranted in order to clarify if the actual amount of neuropathological burden has any influcence on the clinical presentation. Hence, quantification of neuropathology is currently performed in this study group.