In the late 1970s an entity called diffuse Lewy body disease (DLBD) was first described, with LBs seen throughout the brain, including the
cortex. Once thought to be rare it is now assumed that Dementia with Lewy Bodies accounts for 15-25% of elderly demented patients. Age at onset is higher than PD, ranging from 60 to 85 years. The duration
from onset of dementia to death overlaps with AD but is often shorter. In 1995, an international consensus conference was held, establishing clinical criteria for a diagnosis of a new nosologic
entity, DLB. Parkinsonism preceding dementia by an arbitrary interval of 1 year or more is termed PD-D, and dementia that precedes or accompanies the onset of parkinsonism is labeled DLB. Patients with DLB
have an older age at onset and shorter disease duration than patients with typical PD. Resting tremor is less common (55% verses 85%). Patients with DLB have deficits in memory, attention,
language, executive functions, and visuospatial and visuoconstructional abilities. They typically fall in the mild range on the MMSE (22--26). Visual hallucinations are reported (usually well
formed, often benign, but sometimes threatening) in 40% to 75% of patients with DLB. They are usually unprovoked but may be seen frequently in the setting of antiparkinsonian medications. Rapid
eye movement sleep behavior disorder (RBD) is a sleep disturbance that has been associated with Lewy Body disorders (PD and DLB). Supranuclear gaze palsies, although uncommon, have been reported.
Central feature required for a diagnosis of DLB A progressive cognitive decline of sufficient magnitude to interfere with normal social or occupational function. Prominent or persistent memory
impairment may not necessarily occur in the early stages but is usually evident with progression. Deficits on tests of attention and of frontal-subcortical skills and visuospatial
ability may be especially prominent. |
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Core Features for DLB:
Two of the three core features are essential for a diagnosis of probable DLBOne of the three core features is essential for possible DLB |
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a. Fluctuating cognition with pronounced variations in attention and alertness |
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b. Recurrent visual hallucinations that are typically well formed and detailed |
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c. Spontaneous motor features of parkinsonism |
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Features supportive of the diagnosis |
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Transient loss of consciousness |
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Hallucinations in other modalities |
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A diagnosis of DLB is less likely in the presence of: Stroke disease, evident as focal neurologic signs or on brain imagingEvidence on physical examination and investigation
of any physical illness or other brain disorder sufficient to account for the clinical picture |
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