neurologic disorders
Dementia with Lewy Bodies and Parkinson Disease Dementia
Symptoms and Signs
Initial cognitive deterioration in dementia with Lewy bodies resembles Symptoms and Signs . However, dementia with Lewy bodies often manifests with early and prominent deficits in attention, executive function, and visuoperceptual ability; prominent or persistent memory impairment tends to occur as the dementia progresses. Extrapyramidal symptoms(typically including rigidity, bradykinesia, and gait instability) occur. However, in dementia with Lewy bodies (unlike in Parkinson disease), cognitive and extrapyramidal symptoms usually begin within 1 year of each other. Also, the extrapyramidal symptoms differ from those of Parkinson disease; in dementia with Lewy bodies, tremor does not occur early, rigidity of axial muscles with gait instability occurs early, and deficits tend to be symmetric. Repeated falls are common. Fluctuating cognitive functionis a relatively specific feature of dementia with Lewy bodies. Periods of being alert, coherent, and oriented may alternate with periods of being confused and unresponsive to questions, usually over a period of days to weeks but sometimes during the same interview. Memoryis impaired, but the impairment appears to result more from deficits in alertness and attention than in memory acquisition; thus, short-term recall is affected less than digit span memory (ability to repeat 7 digits forward and 5 backward). Patients may stare into space for long periods. Excessive daytime drowsiness is common. Visuospatial and visuoconstructional abilities(tested by block design, clock drawing, or figure copying) are affected more than other cognitive deficits. Visualhallucinationsare common and often threatening, unlike the benign hallucinations of Parkinson disease. Auditory, olfactory, and tactile hallucinations are less common. Delusions occur in 50 to 65% of patients and are often complex and bizarre, compared with the simple persecutory ideation common in Alzheimer disease. Autonomic dysfunctionis common, and unexplained syncope may result. Autonomic dysfunction may occur simultaneously with or occur after onset of cognitive deficits. Extreme sensitivity to antipsychotics is typical. are common. Many patients have Rapid eye movement (REM) sleep behavior disorder , a parasomnia characterized by vivid dreams without the usual physiologic paralysis of skeletal muscles during REM sleep. As a result, dreams may be acted out, sometimes injuring the bed partner. In Parkinson disease dementia (unlike in dementia with Lewy bodies), cognitive impairment that leads to dementia typically begins 10 to 15 years after motor symptoms have appeared. Parkinson disease dementia may affect multiple cognitive domains including attention, memory, and visuospatial, constructional, and executive functions. Executive dysfunction typically occurs earlier and is more common in Parkinson disease dementia than in Alzheimer disease. Psychiatric symptoms (eg, hallucinations, delusions) appear to be less frequent and/or less severe than in dementia with Lewy bodies. In Parkinson disease dementia, postural instability and gait abnormalities are more common, motor decline is more rapid, and falls are more frequent than in Parkinson disease without dementia. 