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Not All Dementia is Alzheimer's Disease.

While Alzheimer's disease (AD) continues to account for 50 to 60% of cases of dementia in older persons and is the most common form of dementia, it is now believed that dementia with Lewy bodies (DLB) is the second most common form in older persons, perhaps accounting for 15 to 25% of all cases. Vascular dementia, previously labeled multi-infarct dementia, now thought to be the third most frequent form of dementia had been held to be the second most frequent dementia occurring among older persons. While a person with dementia may neatly meet the diagnostic criteria for any one of these forms of dementia, they may also have symptoms or features of more than one.

There has also been an increasing interest in Pick's disease, a type of frontotemporal dementia. This probably stems from the fact that Pick's typically has an earlier age of onset than AD or DLB and can be misdiagnosed as a psychiatric condition. This is a relatively rare form of dementia accounting for less than 5% of all dementias.

Accurate diagnosis of dementia type is important since distinguishing between AD and DLB can influence medication used. In addition, increasing caregiver understanding has been shown to increase their ability to cope with the cognitive and behavioral changes associated.

Dementia with Lewy Bodies

The age of onset is typically between the ages of 60 to 80 and males may be a greater risk. The average length of duration is around 6 years but is variable. The disease typically has a rapid, fluctuating progressive course. The key features of DLB include fluctuating cognitive impairment with episodic delirium, prominent psychiatric symptoms including visual hallucinations and some extrapyramidal signs such as rigidity and slowing of and difficulty initiating movements.

Other supporting features of DLB are repeated falls, syncope, and transient losses of consciousness. Neuroleptic sensitivity may also be an important indication of DLB. Medications such as haloperidol can lead to a severe adverse reaction which results in increase extrapyramidal signs. Systematized delusions are also supportive of the diagnosis of DLB. These usually are based on recollection of hallucinations and other perceptual disturbances. As a result, the content of the delusions may be complex and bizarre.

Diagnosis of DLB cannot achieve 100% accuracy until autopsy. Using special staining techniques the distinctive brainstem Lewy bodies and somewhat less distinctive cortical Lewy bodies can be identified with the microscope. The genetics of DLB are not clear and because approximately 75% of DLB cases share AD clinical and pathological features, it is likely to share genetic influences. The presence of the ApoE-4 allele is a risk factor for both AD and DLB. However, the presence of ApoE-4 does not distinguish DLB from AD, nor does its absence rule out either disorder.

Pick's Disease

Pick's disease is a very rare progressive condition. This type of dementia involves the frontal and temporal regions of the brain. Someone suffering from Pick's disease may exhibit changes to personality and behavior before changes to memory functioning are apparent.

The onset of Pick's disease is often before the age of 65 and is usually between the ages of 50 and 60 but can occur as early as age 20 and has been diagnosed at the age of 80. The progression of the illness can take from 2 years to more than 10 years. As noted, behavioral and personality disturbances are early prominent features. For example, the person may become disinhibited and make inappropriate comments in public, be rude or impatient. On the other hand, they may become withdrawn and appear depressed. Overeating can occur and as the disease progresses can evolve to compulsively placing objects in the mouth. As a result, a person with Pick's disease may be misdiagnosed with a psychiatricdisorder. In addition to the behavioral and personality changes, it is often characterized by decreased mental flexibility and reasoning and judgment impairments which are initially greater than any coexisting memory impairments.

Pick's cannot be diagnosed with 100% accuracy until autopsy when microscopic studies can be completed. Using silver-staining, Pick's is defined pathologically by the presence of Pick bodies also called inclusion bodies. These bodies disrupt the ability of the neurons (nerve cells) to work and lead to cell death.

Little is known about the genetics of Pick's disease. Most cases are thought to be sporadic with no other family member affected. However, there are reports of families with what appears to be inherited cases.

Like AD and DLB there is no cure for Pick's disease. Medications can sometimes be used to treat symptoms. However, the most effective treatment remains educating caregivers about the disease to enable them to cope better with the challenges of dealing with the changes this disease brings.

condensed from an article by
Daryl Bohac, PhD.
University of Nebraska Medical Center/Geriatric Center

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