Rapid eye movement (REM) sleep behavior disorder (RBD) is a
sleep disturbance that commonly occurs in Dementia with Lewy
bodies (DLB). Retrospective examination of DLB course has shown
that RBD and cognitive decline may precede the onset of
parkinsonism and visual hallucinations. Therefore, some patients
with DLB may initially present with dementia and RBD, but would
not meet current formal criteria for probable DLB at that time.
The purpose of this study is to determine whether patients with
dementia and RBD, who do not have parkinsonism or visual
hallucinations, have cognitive profiles that can be distinguished
from autopsy-confirmed definite AD, but not from clinically
probable DLB. If so, this would support the hypothesis that
the presence of RBD and dementia, as the only presenting symptoms,
reflects the early manifestation of DLB. Results show that early
dementia in probable DLB and dementia with RBD are
neuropsychologically indistinguishable. Both groups differ from
definite AD of a similar early stage with significantly worse
visual perceptual organization, sequencing and letter fluency
but significantly better confrontation naming and verbal memory.
In addition, follow-up data from a subset of patients with dementia
and RBD reveal the subsequent development of parkinsonism or
hallucinations 1 to 6 years later. Results indicate that the
presentation of dementia and RBD is suggestive of underlying
Lewy body disease and not Alzheimer's disease. This provides
further evidence in support of including RBD as one of the core
diagnostic features of DLB. (JINS, 2002, 8, 907–914.)