by James B. Leverenz, M.D.
Q. Recently, I have heard the term "Lewy body dementia" in the news and literature. What is Lewy body dementia, and how is it different from Alzheimer's disease?
A. Lewy body dementia, officially known as dementia with Lewy bodies (DLB), is a type of dementia that has some of the physical symptoms of Parkinson's disease (PD), such as slowness of movement and gait disturbance. The tremor and rigidity that are also associated with PD are seen with less frequency in DLB.
When someone with DLB or PD has died, and researchers view the brain under the microscope, Lewy bodies are the characteristic changes that occur in the brains of these individuals. They are typically spherical or elliptical in appearance. People with DLB also have some of the changes in the brain that are characteristic of AD (senile plaques and neurofibrillary tangles), but not to the severity of those with AD alone. Rarely, people with DLB have no AD plaques or tangles at all.
Clinically, the primary feature of dementia with Lewy bodies is progressive loss of cognitive and social function, similar to AD. As with AD, memory impairment can involve loss of ability to encode new memories (short-term memory). People with DLB may also have more difficulty with visuospatial tasks such as navigating well-known locations, or copying figures. It is important to note that these differences occur in the early stages of the disease. The distinctions between AD and DLB are less clear once the disease progresses because the cognitive deficits become much broader and more severe.
Behaviorally, psychotic symptoms such as hallucinations occur more frequently and persistently in someone with DLB than they do in someone with AD. Recurrent visual hallucinations are one of the hallmarks of DLB. These hallucianations are well formed in someone with DLB, with patients able to describe fine details. Auditory hallucinations and delusions (incorrect beliefs) also can occur, although they are not as prevalent. People with DLB also have a higher frequency of behavioral problems such as anxiety, apathy and depression.
It is evident that there is a connection between dementia with Lewy bodies, Parkinson's disease and Alzheimer's disease, however the precise link is unclear. Patients with DLB comprise a large portion of dementia cases, second only to AD. Thus, DLB is an important focus for both research and clinical care.n
This article was compiled from the article Dementia with Lewy bodies, James B. Leverenz and Ian G. McKeith, Medical Clinics of North America, Volume 86, 2002, pp 519-535.