Causes Of Dementia
Dementia can be caused by a number of diseases, but the three most common are:
It is not uncommon for a patient to have two of these diseases at the same time. This can initially make a clear-cut diagnosis difficult.
Other conditions that may cause dementia include:
Together, these causes account for less than 20 percent of all cases of dementia. Some conditions, such as Huntington's disease, are extremely rare.
Alzheimer's disease accounts for 40 percent to 45 percent of all cases of dementia. By the time it is detected, it has been present for several months or even years. Characteristic changes occur in the brain and cannot be detected by current laboratory tests. In addition to memory loss, a patient with Alzheimer's disease may show signs of a personality disorder, behavior changes and impaired judgment. Language is also affected. The patient may have difficulty naming objects and reduced spontaneous speech. The patient may constantly repeat words and movements. Coordination becomes increasingly difficult, making simple tasks such as dressing or pouring a drink demanding and frustrating. The combination of impaired judgment and poor coordination makes driving particularly dangerous.
At a late stage of the disease, problems with urinary continence may develop, and patients may wet their beds. The rate of disease progression varies from one individual to another. The duration of the disease ranges from four to 15 years. This means that a patient diagnosed with dementia today can be expected to live for four to 15 years.
Multi-infarct or vascular dementia occurs as a result of narrowing in the blood vessels in the brain. People with this condition have recurrent mini-strokes and show a step-wise deterioration in mental performance. That is, they remain stable for a long period and then decline rapidly. Important points in the disease's progress are brief episodes of weakness in the limbs or facial muscles (affecting one side of the body) or temporary loss of vision. The risk factors for multi-infarct dementia are the same as for stroke:
- Age older than 65 years
- Hypertension (high blood pressure)
- Cigarette smoking
- Heart disease
- Diabetes mellitus
Lewy body disease is a type of dementia with symptoms similar to Parkinson's disease.
Lewy bodies are specific deposits in the brain that result from the degeneration of nerve cells. The buildup of dead nerve cells interferes with brain function. Symptoms of Lewy body disease are similar to those of Alzheimer's and Parkinson's disease. In general, the picture is one of a progressive dementia with relatively well-preserved speech and awareness, slowness of movements and frequent hallucinations. Eye movements are normal, which distinguishes Lewy body disease from other conditions that can present like Parkinson's disease. The length of the illness is variable, but usually symptoms get worse over the years.
Researchers are working to define subtypes of Lewy body disease that will make classification and diagnosis more accurate.
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