Lewy body dementia (LBD) is a type of progressive dementia that leads to a decline in thinking, reasoning and independent function because of abnormal microscopic deposits that damage brain cells over time.
About Lewy body dementia
Most experts estimate that Lewy body dementia is the third most common cause of dementia after Alzheimer's disease and vascular dementia, accounting for 5 to 10 percent of cases.
The hallmark brain abnormalities linked to Lewy body dementia are named after Frederich H. Lewy, M.D., the neurologist who discovered them while working in Dr. Alois Alzheimer's laboratory during the early 1900s. Alpha-synuclein protein, the chief component of Lewy bodies, is found widely in the brain, but its normal function isn't yet known.
Lewy bodies are also found in other brain disorders, including Alzheimer's disease and Parkinson's disease dementia. Many people with Parkinson's eventually develop problems with thinking and reasoning, and many people with Lewy body dementia experience movement symptoms, such as hunched posture, rigid muscles, a shuffling walk and trouble initiating movement.
This overlap in symptoms and other evidence suggest that Lewy body dementia, Parkinson's disease and Parkinson's disease dementia may be linked to the same underlying abnormalities in how the brain processes the protein alpha-synuclein. Many people with both Lewy body dementia and Parkinson's dementia also have plaques and tangles — hallmark brain changes linked to Alzheimer's disease.
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Learn more: Mixed Dementia.
Symptoms of Lewy body dementia include:
- Changes in thinking and reasoning.
- Confusion and alertness that varies significantly from one time of day to another or from one day to the next.
- Slowness, gait imbalance and other parkinsonian movement features.
- Well-formed visual hallucinations.
- Trouble interpreting visual information.
- Sleep disturbances.
- Malfunctions of the "automatic" (autonomic) nervous system.
- Memory loss that may be significant but less prominent than in Alzheimer's.
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As with other types of dementia
, there is no single test that can conclusively diagnose Lewy body dementia. Today, Lewy body dementia is a "clinical" diagnosis, which means it represents a doctor's best professional judgment about the reason for a person's symptoms. The only way to conclusively diagnose Lewy body dementia is through a postmortem autopsy.
Many experts now believe that Lewy body dementia and Parkinson's disease dementia are two different expressions of the same underlying problems with brain processing of the protein alpha-synuclein. But most experts recommend continuing to diagnose Lewy body dementia and Parkinson's dementia as separate disorders.
- The diagnosis is Lewy body dementia when:
- Dementia symptoms consistent with Lewy body dementia develop first.
- When both dementia symptoms and movement symptoms are present at the time of diagnosis.
- When dementia symptoms appear within one year after movement symptoms.
- The diagnosis is Parkinson's disease dementia when a person is originally diagnosed with Parkinson's based on movement symptoms, and dementia symptoms don't appear until a year or more later.
Since Lewy bodies tend to coexist with Alzheimer's brain changes, it may sometimes be hard to distinguish Lewy body dementia from Alzheimer's disease, especially in the early stages.
Key differences between Alzheimer's and Lewy body dementia
- Memory loss tends to be a more prominent symptom in early Alzheimer's than in early Lewy body dementia, although advanced Lewy body dementia may cause memory problems in addition to its more typical effects on judgment, planning and visual perception.
- Movement symptoms are more likely to be an important cause of disability early in Lewy body dementia than in Alzheimer's, although Alzheimer's can cause problems with walking, balance and getting around as it progresses to moderate and severe stages.
- Hallucinations, delusions and misidentification of familiar people are significantly more frequent in early-stage Lewy body dementia than in Alzheimer's.
- REM sleep disorder is more common in early Lewy body dementia than in Alzheimer's.
- Disruption of the autonomic nervous system, causing a blood pressure drop on standing, dizziness, falls and urinary incontinence, is much more common in early Lewy body dementia than in Alzheimer's.
Causes and risks
Researchers have not yet identified any specific causes of Lewy body dementia. Most people diagnosed with Lewy body dementia have no family history of the disorder, and no genes linked to Lewy body dementia have been conclusively identified.
Treatment and outcomes
There are no treatments that can slow or stop the brain cell damage caused by Lewy body dementia. Current strategies focus on helping symptoms.
If your treatment plan includes medications, it's important to work closely with your physician to identify the drugs that work best for you and the most effective doses. Treatment considerations involving medications include the following issues:
- Cholinesterase inhibitor drugs are the current mainstay for treating thinking changes in Alzheimer's. They also may help certain Lewy body dementia symptoms.
- Antipsychotic drugs should be used with extreme caution in Lewy body dementia. Although physicians sometimes prescribe these drugs for behavioral symptoms that can occur in Alzheimer's, they may cause serious side effects in as many as 50 percent of those with Lewy body dementia. Side effects may include sudden changes in consciousness, impaired swallowing, acute confusion, episodes of delusions or hallucinations, or appearance or worsening of Parkinson's symptoms.
- Antidepressants may be used to treat depression, which is common with Lewy body dementia, Parkinson's disease dementia and Alzheimer's. The most commonly used antidepressants are selective serotonin reuptake inhibitors (SSRIs).
- Clonazepam may be prescribed to treat REM sleep disorder.
Like other types of dementia that destroy brain cells, Lewy body dementia gets worse over time and shortens lifespan.