Neuroimaging Findings in Dementia with Lewy Body: A Review

1.1 Dementia with Lewy bodies: An overview Dementia with Lewy bodies (DLB) is a progressive neurodegenerative disorder characterized by the core clinical features of fluctuating consciousness, visual hallucinations and parkinsonism. The term DLB and the clinical criteria were first introduced and proposed by Mc Keith and colleagues in 1996 during the First International Workshop of the Consortium on Dementia with Lewy Bodies (McKeith et al., 1996) and were revised in 2005 to improve the sensitivity for diagnosis (McKeith et al., 2005). Interestingly, in these revised criteria, imaging with Single Photon Emission Computed Tomography (SPECT) or Positron Emission Tomography (PET) played an important role for the first time in the clinical diagnostic criteria of a dementia and was included as a suggestive feature supporting the diagnosis. After Alzheimer's disease (AD), DLB is now considered the second most common type of degenerative dementia in elderly people (Aarsland et al., 2008; McKeith et al., 2004) observed in 15 to 25% of autopsy series (Heidebrink, 2002; McKeith et al., 1996; Perry et al., 1990). These percentages are consistent with the few available epidemiological populationbased studies (de Silva et al., 2003; Herrera et al., 2002; Rahkonen et al., 2003; Stevens et al., 2002; Yamada et al., 2001; Yamada et al., 2002), which have reported the prevalence of DLB ranging from 0 to 30.5% of all dementia cases in individuals older than 65 years and from 0 to 5% in the general population (Zaccai et al., 2005). However, DLB is a regularly misdiagnosed clinical condition, with autopsy reports indicating a higher frequency than that detected in clinical settings (Farina et al., 2009; Mollenhauer et al., 2010). The pathological background of DLB has been a matter of controversy and is a complex issue (see Fig. 1). The core neuropathological finding is the presence of α-synuclein aggregates which form neuronal inclusions called Lewy bodies (LBs). According to the consensus pathological guidelines, based on a semiquantitative scoring of α-synuclein pathology (LBs density and distribution) in specific brain regions, DLB is distinguished into three different phenotypes (brainstem, transitional/limbic, and diffuse neocortical). Moreover, DLB pathological features are often associated to various degrees of AD pathology (i.e. limbic and neocortical spread of LB lesions with or without concomitant AD amyloid plaque pathology).