In people with LBD, abnormal clumps of a protein called alpha-synuclein accumulate in areas of the brain involved in thinking, memory, and movement. The clumps are called “Lewy bodies” after the doctor who discovered them. They build up inside neurons, or nerve cells, in the brain and cause the neurons not to work well and eventually die. Certain chemicals in the brain that act as messengers between cells are also affected. What causes these changes in the brain is not yet fully understood.

Most cases of LBD are not inherited and rarely does more than one family member have the disease. Certain genetic variants may increase the chance of developing dementia with Lewy bodies, but having a genetic variant does not mean that a person will definitely develop the disease.

The most common symptoms of LBD include changes in thinking abilities, movement, sleep, and behavior. The degree of symptoms can vary widely and people with LBD may not have every symptom. Common symptoms include:

• Trouble with attention, planning, multitasking, problem-solving, and reasoning. Memory problems are also common but may not be noticeable early on.
• Problems with visual and spatial abilities, such as judging distance and depth or misidentifying objects.
• Unpredictable changes in concentration, attention, alertness, and wakefulness.
• Visual hallucinations, which occur in up to 80% of people with LBD, often early on.
• Movement changes, such as tremor or muscle stiffness, known as parkinsonism.
• Sleep disorders, including rapid eye movement (REM) sleep behavior disorder in which a person seems to act out dreams while asleep, excessive sleep or lack of sleep, and restless leg syndrome.
• Depression, lack of interest, anxiety, ideas not based in reality, and other changes in mental health.
• Sensitivity to heat and cold, dizziness, poor sense of smell, and other changes in automatic functions of the body.

Individuals with mild symptoms can often function close to normally. As the disease progresses and thinking and movement abilities decline, people with LBD will need more help and may depend on caregivers full time.

The two types of Lewy body dementia — dementia with Lewy bodies and Parkinson’s disease dementia — are caused by the same underlying changes in the brain. Over time, these conditions may result in similar symptoms. The main difference is the timing of when thinking and movement symptoms begin.

In dementia with Lewy bodies, problems with thinking, unpredictable changes in attention and alertness, and visual hallucinations develop early in relation to movement symptoms, such as slow movement, difficulty walking, and muscle stiffness.

In Parkinson’s disease dementia, movement symptoms start first and are consistent with a diagnosis of Parkinson’s disease. Later, problems with thinking and changes in mood and behavior develop. However, not everyone with Parkinson’s disease will develop dementia.

It’s important to know which type of LBD a person has, both to tailor treatment to symptoms and to understand how the disease will likely progress. For example, some people with LBD may not experience significant movement problems, such as frequent falls and shaking, for several years, while others may have them early on. Knowing what to expect can help people with LBD and their families prepare for changes that may need to be made, for example, to help prevent falls.

Dementia with Lewy bodies is often hard to diagnose early because symptoms may at first look like Alzheimer’s or a mental illness such as schizophrenia. LBD can also occur alongside other forms of dementia. Talking to both the patient and family members or caregivers can help doctors make a diagnosis. It is important to tell the doctor about any symptoms involving thinking, movement, sleep, behavior, or mood.

To diagnose LBD, doctors may:

• Ask questions about a person’s medical history and symptoms.
• Perform physical exams and laboratory tests of blood and other fluids.
• Conduct assessments to evaluate memory and other mental functions.
• Do tests to rule out other conditions that could cause similar symptoms. These could include blood tests and brain imaging tests.

Although LBD currently cannot be prevented or cured, treatments may be able to help with some of the symptoms. A treatment plan may involve medications, physical and other types of therapy, and counseling. Changes to make the home safer, equipment to make everyday tasks easier, and social support are also important.

A skilled care team can suggest ways to improve quality of life for both people with LBD and their caregivers. A neurologist should be part of the care team and can help patients and their families work with other types of professionals.