The concept of the clinical syndrome of ‘dementia with Lewy bodies’ arose within the context of correlations with the pathological descriptions of Lewy body inclusions. These inclusions were first described by F. H. Lewy in 1912 in the dorsal motor nucleus of the vagus and substantia innominata (Lewy, 1912), and Lewy bodies in the substantia nigra were postulated to be specific for Parkinson's disease by Tretiakoff in 1919 (Tretiakoff, 1919). Cortical Lewy bodies were initially described in association with postencephalitic parkinsonism (Lipkin, 1959), in elderly with incidental nigral Lewy bodies (Forno, 1969), in severe dementia (Okazaki et al., 1961), and in institutionalized psychiatric patients (Woodward, 1962). From a clinicopathologic study of 20 cases in 1980, K. Kosaka proposed that the neuroanatomical spectrum of Lewy bodies ranged from isolated substantia nigra inclusions to widespread cortical inclusions; he coined the term ‘diffuse Lewy body disease’ to describe a clinical syndrome of parkinsonism, dementia, and/or psychosis associated pathologically with Lewy bodies in cortical and limbic regions in addition to subcortical nuclei (Kosaka et al., 1980). In more recent nomenclature, the clinicopathological syndrome has been termed ‘Dementia with Lewy bodies’ (DLB).
DLB has been recognized as the second most common form of degenerative dementia, after Alzheimer's disease, occurring in 15–36% of pathological series of dementia (Hansen et al., 1990; Holmes et al., 1999; Perry et al., 1990), with an estimated prevalence of 10–25% in hospital and community elderly with dementia (Ballard et al., 1995; Shergill et al., 1994). Furthermore, cortical Lewy bodies are found in more than 25% of AD cases (Bergeron & Pollanen, 1989; Ditter & Mirra, 1987; Forno & Langston, 1993). In a review of autopsy-confirmed cases of DLB and AD, the frequency of males was greater in DLB (M:F 1.7 in DLB vs. 0.53 in AD), the average age of onset was similar (70 years old in DLB, 71 years old in AD), with a trend toward more rapidly progressive illness in DLB (duration 6.25 of years in DLB vs. 7.3 of years in AD) (McKeith & O'Brien, 1999).
The clinical features of DLB have been incorporated into consensus criteria for the clinical diagnosis of DLB (Table 18.1) (McKeith et al., 1996).