Can we clinically diagnose dementia with Lewy bodies yet?

Abstract

Dementia with Lewy Bodies (DLB) was initially identified and confirmed primarily by pathology, but is soon to be incorporated into the Diagnostic and Statistical Manual criteria as a clinical disease entity. Despite these advances over more than 20 years, current data suggest that the sensitivity of accurate clinical diagnosis of DLB is still very low, although there is mounting evidence that supportive features may increase diagnostic accuracy. Although DLB remains easy to identify pathologically with different cellular pathologies differentiating it from other dementia syndromes, pathological identification using only Lewy body pathology has been shown to be inaccurate due to overlap with patients without dementia symptoms. A number of studies now suggest that a combination of cellular pathologies, which include α-synuclein and β-amyloid deposition as well as dopamine denervation, assist with differentiating this dementia syndrome from others. The clinical and pathological overlap with the tauopathy of Alzheimer's disease still remains to be clarified. To determine more robust and independent clinicopathological correlates from Alzheimer's disease, longitudinal prospective studies, using specific clinical batteries on dementia patients reaching the proposed criteria for DLB, with post-mortem assessment of the multiple pathologies associated with dementia, are required. Identifying genetic causes for DLB is another approach to investigate the pathogenesis of DLB. However this approach has been hindered to date by difficulties with identifying DLB clinically. The use of novel techniques is likely to advance knowledge on the pathogenesis of DLB and assist with redefining clinical and pathologic diagnostic criteria. To achieve the goal of more accurate clinical diagnosis of DLB, breakthroughs are necessary on the pathogenesis of DLB.

Figure 1

Lewy-related pathologies (LRP) and Aβ deposition in DLB. (A-C) Histofluorecence identification of α-synuclein-positive (A, green) Lewy bodies using thioflavin S (B, blue) for filament localization (C, merge) showing difficulty with immunostaining the mature core filaments of midbrain Lewy bodies. (D) Eosinophilic Lewy body in a pigmented midbrain dopaminergic neuron, (E) mature α-synuclein-positive Lewy body in the neocortex identified using peroxidase immunohistochemistry, (F) immature α-synuclein-positive Lewy body and related star-shaped α-synuclein-positive astrocytes in the neocortex identified using peroxidase immunohistochemistry. (G) α-synuclein-positive Lewy neurites in the hippocampal CA2 region identified using peroxidase immunohistochemistry, and (H) Aβ-positive cortical plaques identified using peroxidase immunohistochemistry. The scale in F and G is equal to that in E.