Most people associate dementia with Alzheimer's disease. But 1.3 million Americans have another form of dementia called Lewy body dementia or dementia with Lewy bodies. This progressive neurological disorder is named for the Lewy bodies -- tiny deposits of a protein called alpha-synuclein -- found in certain areas of the brain. Over time, these proteins accumulate and cause the death of brain cells. This results in impairments in certain cognitive functions, such as memory, language processing, emotions and behavior, as well as control of movement.
Some experts identify two types of Lewy body dementia: dementia with Lewy bodies, in which cognitive symptoms appear within a year of neurological problems such as slowness of movement and impaired balance, and Parkinson's disease dementia, in which cognitive symptoms appear more than a year after the onset of movement problems.
Difficult to diagnose. No specific brain scans or lab tests can pinpoint the presence of Lewy body dementia, although a type of scan, DAT, or dopamine transporter SPECT scan, can support the diagnosis. Diagnosis of Lewy body dementia is based on identifying the symptoms -- which can vary widely in severity from person to person -- and then ruling out other possible causes such as certain drugs.
The progressive decline of mental function is the primary symptom of Lewy body dementia, but what sets it apart from Alzheimer's disease is the presence of subtle symptoms referred to as parkinsonism because they're not fully suggestive of Parkinson's disease and because hallucinations are common at the beginning of Lewy body dementia. Some symptoms common to early Lewy body dementia and other forms of dementia include:
- Memory loss, difficulty with reasoning, problem solving, visual and spatial judgment and multitasking
- Behavior and mood changes, including depression, anxiety and delusions
- Sleep problems
Certain symptoms are more pronounced in Lewy body dementia than in other forms of dementia:
- Movement difficulties, such as muscle rigidity, a shuffling gait, tremors and loss of coordination, are similar to Parkinson's symptoms but appear more spontaneously.
- Unlike with Alzheimer's, acute episodes of drowsiness and worsened cognition are common, accompanied by worsening attention, focus and alertness. The fluctuation in mental alertness occurs intermittently and can vary from day to day and even hour to hour.
- Vivid hallucinations appear in the early stages of the disease, whereas they tend to occur in later stages of Alzheimer's.
- Sleep problems, particularly REM (rapid eye movement) sleep behavior disorder -- in which the patient acts out dreams, may move in ways that appear violent and may fall out of bed -- may start years before memory symptoms and cause excessive daytime sleepiness.
- Falls, delusions, brief episodes of unconsciousness and fainting are common.
- The part of the nervous system that regulates automatic actions may be affected, resulting in fluctuations in blood pressure, heart rate and body temperature; sexual dysfunction; constipation; or dry eyes or mouth.
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