Dementia with Lewy bodies: early diagnostic challenges

Abstract

Dementia with Lewy bodies (DLB) is defined pathologically as neurodegeneration associated with Lewy bodies (LB). LB-related symptoms, including olfactory dysfunction, dysautonomia, and mood and sleep disorders, are increasingly recognized as clinical signs that enable the early detection of DLB, because these symptoms often antedate dementia by years or even decades. It remains unknown if the clinical history of LB-related symptoms is sufficient for the prodromal state of DLB to be suspected in memory clinics. We retrospectively investigated the clinical courses, including olfactory dysfunction, dysautonomia, depression, and rapid eye movement sleep behaviour disorder, of 90 patients with probable DLB. The timing of LB-related symptoms that preceded or followed relative to the onset of memory loss was calculated. LB-related symptoms were present in 79 of 90 patients (87.8%) with probable DLB before or at the time of memory loss onset. These symptoms preceded the onset of memory loss between 1.2 and 9.3 years. We also report on four non-demented patients with a clinical history of LB-related symptoms in our memory clinic. All four patients showed reduced cardiac [(123) I]-metaiodobenzylguanidine levels. Moreover, [(18) F]fluoro-D-glucose positron emission tomography scans revealed glucose hypometabolism in the occipital cortex in two patients. One patient converted to probable DLB with the development of parkinsonism 2 years after major depression was diagnosed. Based on a clinical history of LB-related symptoms, we propose a conceptual framework to identify these symptomatic but non-demented individuals that led us to suspect the underlying pathophysiology of Lewy body disease. Further prospective study is warranted to determine the clinical significance of LB-related symptoms in non-demented patients.

Keywords: Alzheimer's disease; DLB; Parkinson's disease; REM sleep behaviour disorder; mild cognitive impairment; olfactory dysfunction.