Dementia with lewy bodies and parkinson disease dementia

[Lanell]

Lewy body dementia includes clinically diagnosed dementia with Lewy bodies and Parkinson disease dementia. Dementia with Lewy bodies is chronic cognitive deterioration characterized by cellular inclusions called Lewy bodies in the cytoplasm of cortical neurons. Parkinson disease dementia is cognitive deterioration characterized by Lewy bodies in the substantia nigra; it develops late in Parkinson disease.
(See also Overview of Delirium and Dementia and Dementia.)
Dementia is chronic, global, usually irreversible deterioration of cognition.
Dementia with Lewy bodies is the 3rd most common dementia. Age of onset is typically gt; 60.
Lewy bodies are spherical, eosinophilic, neuronal cytoplasmic inclusions composed of aggregates of alpha-synuclein, a synaptic protein. They occur in the cortex of some patients who have dementia with Lewy bodies. Neurotransmitter levels and neuronal pathways between the striatum and the neocortex are abnormal.
Lewy bodies also occur in the substantia nigra of patients with Parkinson disease, and dementia (Parkinson disease dementia) may develop late in the disease. About 40% of patients with Parkinson disease develop Parkinson disease dementia, usually after age 70 and about 10 to 15 years after Parkinson disease has been diagnosed.
Because Lewy bodies occur in dementia with Lewy bodies and in Parkinson disease dementia, some experts think that the 2 disorders may be part of a more generalized synucleinopathy affecting the central and peripheral nervous systems. Lewy bodies sometimes occur in patients with Alzheimer disease, and patients with dementia with Lewy bodies may have neuritic plaques and neurofibrillary tangles. Dementia with Lewy bodies, Parkinson disease, and Alzheimer disease overlap considerably. Further research is needed to clarify the relationships among them.
Both dementia with Lewy bodies and Parkinson disease dementia have a progressive course with a poor prognosis.
Dementia should not be confused with delirium, although cognition is disordered in both. The following usually helps distinguish dementia from delirium:

Dementia affects mainly memory, is typically caused by anatomic changes in the brain, has slower onset, and is generally irreversible.
Delirium affects mainly attention, is typically caused by acute illness or drug toxicity (sometimes life threatening), and is often reversible.

Other specific characteristics also help distinguish the dementia and delirium (see table Differences Between Delirium and Dementia).