Dementia with Lewy bodies (DLB) 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 dementia with Lewy bodies
Most experts estimate that dementia with Lewy bodies is the third most common cause of dementia after Alzheimer's disease and vascular dementia, accounting for 10 to 25 percent of cases.
The hallmark brain abnormalities linked to DLB 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 DLB 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 DLB, 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 DLB and Parkinson's dementia also have plaques and tangles — hallmark brain changes linked to Alzheimer's disease. Sign up for our e-news to receive updates about Alzheimer’s and dementia care and research.
Learn more: Mixed Dementia.
Symptoms of dementia with Lewy bodies 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.
- Parkinson's symptoms, such as a hunched posture, balance problems and rigid muscles.
- Visual hallucinations.
- Trouble interpreting visual information.
- Acting out dreams, sometimes violently, a problem known as rapid eye movement (REM) sleep disorder.
- Malfunctions of the "automatic" (autonomic) nervous system.
- Memory loss that may be significant but less prominent than in Alzheimer's.
As with other types of dementia
, there is no single test that can conclusively diagnose dementia with Lewy bodies. Today, DLB 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 DLB is through a postmortem autopsy.
Many experts now believe that DLB 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 DLB and Parkinson's dementia as separate disorders.
- The diagnosis is DLB when:
- Dementia symptoms consistent with DLB 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 DLB from Alzheimer's disease, especially in the early stages.
Key differences between Alzheimer's and DLB
- Memory loss tends to be a more prominent symptom in early Alzheimer's than in early DLB, although advanced DLB 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 DLB 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 DLB than in Alzheimer's.
- REM sleep disorder is more common in early DLB 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 DLB than in Alzheimer's.
Causes and risks
Researchers have not yet identified any specific causes of dementia with Lewy bodies. Most people diagnosed with DLB have no family history of the disorder, and no genes linked to DLB have been conclusively identified.
Treatment and outcomes
There are no treatments that can slow or stop the brain cell damage caused by dementia with Lewy bodies. 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 inhibitors drugs are the current mainstay for treating thinking changes in Alzheimer's. They also may help certain DLB symptoms.
- Antipsychotic drugs should be used with extreme caution in DLB. 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 DLB. 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 DLB, 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, DLB gets worse over time and shortens lifespan.