Definition and Overview
Dementia with Lewy bodies is a degenerative dementia caused by the widespread accumulation of Lewy bodies, which are abnormal aggregates of alpha-synuclein protein, in the cerebral cortex and limbic system. It accounts for approximately 4-5% of clinically diagnosed degenerative dementia, and even higher rates are reported in autopsy-based neuropathological studies. It is one of the most common neurodegenerative diseases following Alzheimer's disease and Parkinson's disease.
Lewy body dementia shares the same alpha-synuclein pathology as Parkinson's disease dementia. If cognitive decline occurs before or within a year of Parkinson's motor symptoms, it is classified as Lewy body dementia, and if dementia appears several years before motor symptoms, it is classified as Parkinson's disease dementia.
In ICD-10, it is classified as G31.83.
Causes and Pathophysiology
The core pathology is Lewy bodies and Lewy neurites, which are abnormal aggregates of alpha-synuclein protein. As these aggregates are deposited throughout the brainstem, limbic system, and cerebral cortex, nerve cells lose their function and are lost. Several neurotransmitter systems, including dopamine and acetylcholine, are damaged together, and cholinergic nerve deficiency is particularly prominent, acting as a mechanism for cognitive fluctuations and hallucinations.
In a significant number of patients, amyloid beta and tau pathology of Alzheimer's disease coexists, and this co-occurrence pathology influences the rate of progression and clinical presentation.
core symptoms
cognitive fluctuations
Attention, level of alertness, and clarity of consciousness fluctuate markedly depending on the time of day or day. The dazed state appears repeatedly, and the same patient sometimes appears relatively clear and at other times appears confused.
repetitive hallucinations
Specific and clearly defined visual hallucinations appear repeatedly. It is common for people or animals to be seen, and the fact that it appears from an early stage is an important clue to diagnosis.
Parkinsonism
It is accompanied by Parkinsonian motor symptoms such as bradykinesia, rigidity, and postural instability. Resting tremor tends to be less pronounced than in idiopathic Parkinson's disease.
REM sleep behavior disorder
This is a symptom of turning dreams into action, screaming or flailing one's arms and legs while sleeping, and may appear years before cognitive decline. This period is considered prodromal Lewy body dementia.
In addition, autonomic dysfunction, such as orthostatic hypotension, constipation, and urinary disorders, and hypersensitivity to antipsychotic drugs are accompanied.
diagnosis
Diagnosis follows the 4th consensus criteria (McKeith criteria) of the DLB Consortium in 2017. Cognitive fluctuations, repetitive visual hallucinations, Parkinsonism, and REM sleep behavior disorder are considered key clinical features, and the certainty of diagnosis is determined using their combination and biomarkers.
- History taking: Checking cognitive changes, visual hallucinations, behavior during sleep, and motor symptoms through guardians
- Neuropsychological test: Assessment of decline in attention and visuospatial function
- Dopamine transporter imaging test (DAT scan): Confirmation of loss of dopamine neurons in the basal ganglia
- Myocardial MIBG scintigraphy: confirms cardiac sympathetic dysfunction.
- Polysomnography: Confirmation of loss of muscle tension during REM sleep
In 2020, diagnostic criteria for prodromal Lewy body dementia were proposed to evaluate the stage before cognitive decline begins.
Treatment and Precautions
There is no cure, and the goal is to control symptoms and maintain quality of life.
Cognition and visual hallucinations
Cholinesterase inhibitors (donepezil, rivastigmine) help control cognitive function and visual hallucinations. Due to the nature of the disease, in which cholinergic deficiency is prominent, there are cases where the response can be similar to or better than that seen in Alzheimer's disease.
Antipsychotic hypersensitivity
Approximately half of patients develop severe hypersensitivity to antipsychotic drugs, which can lead to decreased consciousness, rapid worsening of parkinsonism, and increased risk of death. Therefore, non-pharmacological approaches are given priority for hallucinations or agitation, and if drugs are unavoidable, select them carefully and use them in the lowest dose.
Parkinsonism and accompanying symptoms
Dopamine drugs are used for Parkinson's motor symptoms, but dosage adjustment is necessary as they can worsen hallucinations. It concurrently manages autonomic symptoms such as orthostatic hypotension and constipation and sleep disorders.