Lewy body disease, as a postmortem finding, was reported in an 84-year-old man with a 20-year history of RBD, but without any clinically detected neurological disorder (Uchiyama et al., 1995). Postmortem histopathological examination revealed that the patient had Lewy body disease with marked decrease of pigmented neurons in the locus ceruleus and substantia nigra. These findings represent the first documented evidence of a loss of brain stem monoaminergic neurons in clinically idiopathic RBD, and suggest that Lewy body disease might provide an explanation for idiopathic RBD in elderly patients. This report is important in that it calls attention to the possibility that a sizable subgroup of RBD patients with presumed idiopathic RBD may, in fact, turn out to have Lewy body disease as the neuropathological basis of RBD.
A subsequent report involved the case of a 73-year-old man with a 2-year history of parkinsonism and a 15-year history of RBD (Negro and Faber, 1996). The clinical history satisfied operational diagnostic criteria for dementia of the Lewy body type (i.e., mix of parkinsonian symptoms, coarse dementia, fluctuating cognitive performance, and intermittent psychotic symptoms).
Probable diffuse Lewy body dementia was reported in a 72-year-old man with a 17-year history of RBD and a 2 year history of dementia (Turner et al, 1997). The patient had a typically placid disposition during the daytime, but would attack his wife and attempt to choke her during sleep. Cognitive dysfunction began insidiously, but eventually became the dominant clinical concern. He subsequently developed visual hallucinations and illusions in the late afternoon and evening and often thought his wife was an identical imposter. There was marked fluctuation of cognitive capacities, ranging from relatively lucid intervals to intervals of severe cognitive compromise.
Another case was reported of an elderly male patient with RBD and the Lewy body variant of AD identified by postmortem ubiquitin staining (Schenck et al, 1996a; Schenck et al, 1997a).
The potentially close association between Lewy body disease and RBD has been further explored in a study entitled, "REM sleep behavior disorder and degenerative dementia with or without parkinsonism: a syndrome predictive of Lewy body disease?" (Boeve et al, 1997). A group of 21 patients was evaluated, with 90% (n = 19) being male. Two subgroups were compared: one group (.n = 11) with two or more clinical signs of parkinsonism, with mean age of dementia onset of 67 years; a second group (n = 10) without parkinsonism, with mean age of dementia onset of 59 years. The clinical features of RBD and dementia in both groups were remarkably similar, with fluctuating cognitive status and visual hallucinations being common. The authors hypothesized that the underlying pathology in both groups was likely to be diffuse Lewy body disease or the Lewy body variant of AD. Two subsequent studies by the same group of investigators (Boeve et al., 1998; Ferman et al., 1999) on RBD patients with dementia implicate Lewy body disease as the basis of both the RBD and the dementia.
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