The lewy body dementias: Dementia with lewy bodies and related syndromes

Abstract

The Lewy body dementias comprise disorders characterized by parkinsonism and a dementia syndrome with a predominant attentional, executive and visuospatial component, and with the Lewy body as the core pathological marker. Dementia with Lewy bodies (DLB) and Parkinson’s disease with dementia (PDD) are two conditions that meet this definition and are only differentiated by the duration of parkinsonism prior to dementia onset. The standardized clinical criteria for DLB establish an arbitrary 1-year cutoff between symptoms: if dementia begins at the same time or within 1 year of parkinsonism, the patient is presumed to suffer from DLB; if dementia onset occurs more than 1 year after parkinsonism, PDD is assumed. The third report of the DLB consortium [1] highlighted the unresolved boundary issues between DLB and PDD but maintained this arbitrary cut point. The appropriateness of such an artificial cut point for differentiating two similar clinical syndromes has been debated. Indeed, DLB and PDD share many common characteristics and might represent different clinical manifestations of a common underlying process. Even within the PDD group, different cognitive profiles exist [2, 3], and some genetic alterations cause both PDD and DLB within the same family [4]. Thus, it is reasonable to consider these conditions as a continuum of possible symptoms: different patient profiles can be identified but with considerable overlap between groups. For this reason, progressive focus has shifted to defining the early stages of these diseases, where differences may be more apparent or clinically recognizable. In this chapter, we aim to present what is currently known about DLB and PDD, focusing on clinical aspects of diagnosis, treatment, and care as well as a taste of foreseeable developments in the near future.