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Dementia With Lewy Bodies and Parkinson Disease Dementia


Juebin Huang

, MD, PhD, Department of Neurology, University of Mississippi Medical Center

Reviewed/Revised Feb 2023

Dementia with Lewy bodies is progressive loss of mental function characterized by the development of Lewy bodies in nerve cells. Parkinson disease dementia is loss of mental function characterized by the development of Lewy bodies in people who have Parkinson disease.

  • People who have dementia with Lewy bodies fluctuate between alertness and drowsiness and may have hallucinations, difficulty drawing, and difficulty moving that is similar to that due to Parkinson disease.

  • Parkinson disease dementia typically develops about 10 to 15 years after other symptoms of Parkinson disease.

  • Diagnosis is based on symptoms.

  • Strategies are used to prolong functioning as long as possible, and the medications used to treat Alzheimer disease may help.

Dementia with Lewy bodies is the third most common type of dementia. Dementia with Lewy bodies usually develops in people older than 60.

About 40% of people with Parkinson disease Parkinson Disease (PD) Parkinson disease is a slowly progressive degenerative disorder of specific areas of the brain. It is characterized by tremor when muscles are at rest (resting tremor), increased muscle tone... read more develop Parkinson disease dementia. The dementia usually develops after age 70 and about 10 to 15 years after Parkinson disease is diagnosed.

Dementia differs from delirium Delirium Delirium is a sudden, fluctuating, and usually reversible disturbance of mental function. It is characterized by an inability to pay attention, disorientation, an inability to think clearly... read more , which is characterized by an inability to pay attention, disorientation, an inability to think clearly, and fluctuations in the level of alertness.

  • Dementia affects mainly memory, and delirium affects mainly attention.

  • Dementia typically begins gradually and has no definite beginning point. Delirium begins suddenly and often has a definite beginning point.

Changes in the brain

In dementia with Lewy bodies and Parkinson disease dementia, abnormal round deposits of a protein (called Lewy bodies) form in nerve cells. Lewy bodies result in the death of nerve cells.

In dementia with Lewy bodies, the Lewy bodies form throughout the outer layer of the brain (gray matter, or cerebral cortex). The cerebral cortex, which is the largest part of the brain, is responsible for thinking, perceiving, and using and understanding language.

In Parkinson disease dementia, the Lewy bodies tend to form in part of the brain called the substantia nigra, the part that is affected in Parkinson disease. The substantia nigra is located deep within the brain stem and helps make movements smooth. The brain stem connects the brain with the spinal cord.

Dementia with Lewy bodies and Parkinson disease dementia may be variations of one disorder. In this disorder, synuclein (a protein in the brain that helps nerve cells communicate) changes shape (misfolds) and slowly accumulates mostly in the brain but also in the digestive tract and heart. These abnormal deposits of synuclein are called Lewy bodies. The misfolded synuclein in Lewy bodies triggers more synuclein to misfold, resulting in the formation of more Lewy bodies. Brain damage results from the accumulation of Lewy bodies. Misfolded proteins that cause brain damage in this way are called prions Overview of Prion Diseases Prion diseases are rare progressive, fatal, and currently untreatable degenerative disorders of the brain (and rarely of other organs) that result when a protein changes into an abnormal form... read more . Prions cause other brain disorders such as Creutzfeld-Jacob disease Creutzfeldt-Jakob Disease (CJD) Creutzfeldt-Jakob disease is a prion disease characterized by progressive deterioration of mental function, leading to dementia, involuntary jerking of muscles (myoclonus), and staggering when... read more .

Lewy bodies also develop in some people with Alzheimer disease, although neurofibrillary tangles and neuritic (senile) plaques seem to be the main source of damage. Neurofibrillary tangles and neuritic plaques, typical in Alzheimer disease Alzheimer Disease Alzheimer disease is a progressive loss of mental function, characterized by degeneration of brain tissue, including loss of nerve cells, the accumulation of an abnormal protein called beta-amyloid... read more , sometimes develop in people who have dementia with Lewy bodies. Dementia with Lewy bodies, Parkinson disease dementia, and Alzheimer disease overlap considerably, and more research is needed to clarify their relationships.


Dementia with Lewy bodies

The symptoms of dementia with Lewy bodies are very similar to those of Alzheimer disease. They include memory loss, disorientation, and problems remembering, thinking, understanding, communicating, and controlling behavior. But dementia with Lewy bodies can be distinguished by the following:

In dementia with Lewy bodies, hallucinations are usually visual ones, which are often complex and detailed. They may include recognizable animals or people. The hallucinations are often threatening. Over half of people who have dementia with Lewy bodies have complex, bizarre delusions. Instead of relieving these symptoms, antipsychotic medications Antipsychotic drugs Schizophrenia is a mental disorder characterized by loss of contact with reality (psychosis), hallucinations (usually, hearing voices), firmly held false beliefs (delusions), abnormal thinking... read more often make them and other symptoms worse or have other severe, sometimes life-threatening side effects, such as neuroleptic malignant syndrome. Neuroleptic Malignant Syndrome Neuroleptic malignant syndrome is confusion or unresponsiveness, muscle rigidity, high body temperature, and other symptoms that occur when certain antipsychotic (neuroleptic) drugs or anti-vomiting... read more

Like people who have Parkinson disease, people who have dementia with Lewy bodies have stiff muscles, move slowly and sluggishly, shuffle when they walk, and stoop over. Balance is easily lost, making falls more likely. Tremor also develops, but it usually develops later and causes fewer problems than it does in Parkinson disease. Problems with thinking and problems with muscles and movement usually begin within 1 year of each other.

The autonomic nervous system Overview of the Autonomic Nervous System The autonomic nervous system regulates certain body processes, such as blood pressure and the rate of breathing. This system works automatically (autonomously), without a person’s conscious... read more Overview of the Autonomic Nervous System may malfunction, preventing the body from regulating internal functions, such as blood pressure and body temperature. As a result, people may faint, sweat too much or too little, have a dry mouth, or have urinary problems or constipation.

After symptoms appear, people usually live about 6 to 12 years.

Parkinson disease dementia

In Parkinson disease dementia (unlike in dementia with Lewy bodies), mental function typically begins to deteriorate about 10 to 15 years after problems with muscles and movement appear.

As in other dementias, many mental functions can be affected. Memory is impaired, and people have difficulty paying attention and processing information. People think more slowly. Problems with planning and doing complex tasks occur earlier and are more common than in Alzheimer disease.

Hallucinations and delusions are less common and/or less severe than in dementia with Lewy bodies.

In Parkinson disease dementia, problems with balance and walking and falls are more common, and muscle problems (such as stiffness and slowed movements) worsen more rapidly than in Parkinson disease without dementia.


  • A doctor's evaluation

  • Computed tomography or magnetic resonance imaging

Doctors must determine whether a person has dementia and, if so, whether the dementia is dementia with Lewy bodies or Parkinson disease dementia.

Diagnosis of dementia

A diagnosis of dementia is based on the following:

  • Symptoms, which are identified by asking the person and family members or other caregivers questions

  • Results of a physical examination

  • Results of a mental status test

  • Results of additional tests, such as computed tomography (CT) or magnetic resonance imaging (MRI)

The mental status test Mental Status Testing Mental Status Testing , consisting of simple questions and tasks, helps doctors determine whether people have dementia.

Neuropsychologic testing, which is more detailed, is sometimes needed. This testing covers all the main areas of mental function, including mood, and usually takes 1 to 3 hours. This testing helps doctors distinguish dementia from age-associated memory impairment Dementia , mild cognitive impairment Dementia , and depression Dementia .

Information from the above sources helps doctors usually rule out delirium as the cause of symptoms (see table Comparing Delirium and Dementia Comparing Delirium and Dementia Comparing Delirium and Dementia ). Doing so is essential because delirium, unlike dementia, can often be reversed if promptly treated.

Distinguishing delirium from dementia with Lewy bodies is particularly important because in both, mental function also fluctuates.

Diagnosis of dementia with Lewy bodies and Parkinson disease dementia

Doctors base the diagnosis of dementia with Lewy bodies on its characteristic symptoms. Dementia with Lewy bodies is likely if mental function fluctuates in people who have visual hallucinations and muscle and movement symptoms similar to those caused by Parkinson disease.

Computed tomography (CT) and/or magnetic resonance imaging (MRI) may be done to rule out other causes of dementia.

However, even after testing, distinguishing dementia with Lewy bodies from Parkinson disease dementia can be difficult because symptoms are similar:

  • Generally, dementia with Lewy bodies is more likely if movement and muscle problems develop at the same time or shortly after mental function starts to decline.

  • Parkinson disease dementia is more likely if mental decline occurs years after muscle and movement problems develop in people with Parkinson disease and if muscle and movement symptoms are more severe than mental impairment.

However, the diagnosis of these dementias can be confirmed definitively only when a sample of brain tissue is removed and examined under a microscope. This procedure is done after death during an autopsy.


  • Safety and supportive measures

  • Medications used to treat Alzheimer disease

Treatment of dementia with Lewy bodies and Parkinson disease dementia involves general measures to provide safety and support, as for all dementias.

Safety and supportive measures

Generally, the environment should be bright, cheerful, safe, stable, and designed to help with orientation. Some stimulation, such as a radio or television, is helpful, but excessive stimulation should be avoided.

Structure and routine help people stay oriented and give them a sense of security and stability. Any change in surroundings, routines, or caregivers should be explained to people clearly and simply.

Following a daily routine for tasks such as bathing, eating, and sleeping helps people with Alzheimer disease remember. Following a regular routine at bedtime may help them sleep better.

Activities scheduled on a regular basis can help people feel independent and needed by focusing their attention on pleasurable or useful tasks. Such activities should include physical and mental activities. Activities should be broken down in small parts or simplified as the dementia worsens.


Medications used to treat Parkinson disease Drugs Used to Treat Parkinson Disease Drugs Used to Treat Parkinson Disease may help relieve the symptoms of Parkinson disease (such as stiff muscles and tremor) in both dementias. However, in dementia with Lewy bodies, these medications may worsen confusion, hallucinations, and delusions.

Pimavanserin, an antipsychotic medication, can be used to treat hallucinations and delusions in people with Parkinson disease.

Care for caregivers

Caring for people with dementia is stressful and demanding, and caregivers may become depressed and exhausted, often neglecting their own mental and physical health. The following measures can help caregivers (see table Caring for Caregivers Caring for Caregivers Caring for Caregivers ):

  • Learning about how to effectively meet the needs of people with dementia and what to expect from them: Caregivers can get this information from nurses, social workers, organizations, and published and online materials.

  • Seeking help when it is needed: Caregivers can talk to social workers (including those in the local community hospital) about appropriate sources of help, such as day-care programs, visits by home nurses, part-time or full-time housekeeping assistance, and live-in assistance. Counseling and support groups can also help.

  • Caring for self: Caregivers need to remember to take care of themselves. They should not given up their friends, hobbies, and activities.

End-of-life issues

Before people with dementia with Lewy bodies or Parkinson disease dementia become too incapacitated, decisions should be made about medical care, and financial and legal arrangements should be made. These arrangements are called advance directives Advance Directives Health care advance directives are legal documents that communicate a person’s wishes about health care decisions in the event the person becomes incapable of making health care decisions. There... read more . People should appoint a person who is legally authorized to make treatment decisions on their behalf (a health care proxy). They should discuss their health care wishes Treatment Options at the End of Life Often, the available choices for end-of-life care involve a decision whether to accept the likelihood of dying sooner but to be more comfortable or attempt to live slightly longer by receiving... read more with this person and their doctor. Such issues are best discussed with all concerned long before decisions are necessary.

As the dementia worsens, treatment tends to be directed at maintaining the person’s comfort rather than at attempting to prolong life.

More Information

The following English-language resources may be useful. Please note that THE MANUAL is not responsible for the content of these resources.

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