Harvard Men's Health Watch

Ask the doctor: Different dementias

Q. My sister was recently diagnosed with dementia with Lewy bodies. How does this differ from dementia because of Alzheimer's disease?

A. Alzheimer's disease is the most common cause of dementia in older people, but it is only one of many causes. Your sister's condition, dementia with Lewy bodies (DLB), is actually the second most common type of dementia. Lewy bodies are clumps of proteins found in the brain cells of people diagnosed with DLB, as well as in people with certain other degenerative neurologic conditions, like Parkinson's disease. Although the symptoms of Alzheimer's disease and dementia with Lewy bodies overlap substantially, there are some that are more typical of DLB.

What all forms of dementia have in common is the loss of higher brain functions, including memory, language, judgment, logic, and visual-spatial skills. A number of conditions cause these problems, and are therefore grouped together as dementias. They include vascular dementia, frontotemporal dementia, and dementia associated with Parkinson's disease. Dementia can progress slowly (over a decade) or more rapidly (within a few years). Doctors usually distinguish between different dementias based on the symptoms, although sometimes MRI or CT scans can help.

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