.
Chapters

0:00 Introduction
1:00 Symptoms of Lewy Body Dementia
1:55 Causes of Lewy Body Dementia
2:26 Treatment of Lewy Body Dementia


Lewy body dementias are two similar and common subtypes of dementia[1]—dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD).[2][3][4][5] Both are characterized by changes in thinking, movement, behavior, and mood.[1] The two conditions have similar features and may have similar causes, and are believed to belong on a spectrum of Lewy body disease[2] that includes Parkinson's disease.[5] As of 2014, they were more often misdiagnosed than any other common dementia.[6]

The exact cause is unknown, but involves widespread deposits of abnormal clumps of protein that form in neurons of the diseased brain. Known as Lewy bodies (discovered in 1912 by Frederic Lewy[7]) and Lewy neurites, these clumps affect both the central nervous system and the autonomic nervous system.[8] The fifth revision of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) gives Lewy body disease as the causative subtype of dementia with Lewy bodies, and Parkinson's disease as the causative subtype of Parkinson's disease dementia.[9] Dementia with Lewy bodies is marked by the presence of Lewy bodies primarily in the cortical regions, and Parkinson's disease dementia with Lewy bodies primarily in the subcortical basal ganglia.[10] The synucleinopathies (dementia with Lewy bodies, Parkinson's disease dementia, and Parkinson's disease) are characterized by shared features of parkinsonism motor symptoms, neuropsychiatric symptoms, impaired cognition, sleep disorders, and visual hallucinations.[11][12] The Lewy body dementias—dementia with Lewy bodies (DLB), and Parkinson's disease dementia (PDD)—are distinguished by the timing when cognitive and motor symptoms appear.[13] The two Lewy body dementias are often considered to belong on a spectrum of Lewy body disease that includes Parkinson's disease.[2][5]

MeSH lists Lewy body disease in several categories: as a nervous system disease in two listings one as a basal ganglia Parkinsonian movement disorder and the other under brain disease as a dementia; as a neurodegenerative disorder listed as a synucleinopathy; and as a neurocognitive disorder listed with dementia.[14]
Cause and mechanisms
Further information: Dementia with Lewy bodies § Pathophysiology

Dementia with Lewy bodies and Parkinson's disease dementia are similar in many ways, suggesting there may be a common pathophysiological mechanism, with PDD and DLB at opposite ends of a Lewy body disease spectrum,[2] and a shared component of protein deposits in Lewy bodies and Lewy neurites.[15] Lewy bodies and neurites have been found to develop from the aggregation of misfolded alpha-synuclein, a protein thought to assist in neurotransmitter release and vesicle turnover; whether these misfolded proteins are responsible for the neurodegenerative effects remains unclear, and no definitive link between Lewy bodies and neurodegenerative effects has been found.[16] DSM-5 gives Lewy body disease as the causative subtype of DLB, and Parkinson's disease as the causative subtype of PDD.[9] DLB is marked by the presence of Lewy bodies primarily in the cortical regions, and PDD with Lewy bodies primarily in the subcortical basal ganglia.[10]

Despite differences in the timing of the appearance of symptoms, the two dementias "show remarkably convergent neuropathological changes at autopsy".[2] The relationship between Parkinson's disease dementia and dementia with Lewy bodies is unclear as of 2020, but there is likely to be genetic overlap, and the two conditions may represent different points on a continuum.[17]
Diagnosis
Further information: Dementia with Lewy bodies § Diagnosis

Dementia with Lewy bodies and Parkinson's disease dementia have similar neuropathological features, but these features are highly variable and the conditions cannot be distinguished on pathological features alone.[16] Generally, dementia with Lewy bodies is distinguished from Parkinson's disease dementia by the time frame in which dementia symptoms appear relative to parkinsonian symptoms and is diagnosed when cognitive symptoms begin before or at the same time as parkinsonism. Parkinson's disease dementia is the diagnosis when Parkinson's disease is already well established before the dementia occurs.[12]