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You are here : 3-RX.com > Medical Encyclopedia > Diseases and Conditions > Dementia
      Category : Health Centers > Mental Health (Mental Disorders)


Alternate Names : Senility

Overview, Causes, & Risk Factors | Symptoms & Signs | Diagnosis & Tests | Prevention & Expectations | Treatment & Monitoring

Dementia is not a disease. It is a group of symptoms marked by gradual changes in brain function and the ability to think, reason, and remember. Serious changes in memory, personality, and behavior are the hallmarks of dementia.

What is going on in the body?

The ability of the brain to work correctly depends on a complex communication system among billions of neurons, or brain cells. Certain parts of the brain are in charge of creating a memory. Others catalog this memory. Still others retrieve it. The way that a brain functions could be compared to the workings of a computer.

If an area of the brain in charge of these special functions is damaged, dementia may occur. Damage may be caused by infection, loss of blood supply, chemicals, or a genetic tendency for losing neurons. People normally lose a certain number of brain cells as they age. However, major losses cause progressive and widespread loss of normal brain function.

In normal aging, memory loss is usually slow. It may result in forgetting names, phone numbers, or where an item was just placed. Intelligence and problem-solving skills are not affected. True dementia involves loss of intelligence and problem-solving skills. It often cannot be reversed and will become worse over time.

What are the causes and risks of the condition?

Dementia is always caused by an underlying disease or condition. Brain tissue is damaged, and the ability to function decreases. Some of these conditions can be reversed, while others cannot. The most common cause of dementia is Alzheimer disease. In this disease, changes in nerve cells in some parts of the brain result in the death of large numbers of cells. The result is a progressive, but slow, decline in memory and thought processes.

Another common form of dementia is multi-infarct dementia. With this condition, small strokes or changes in the blood supply to the brain from the narrowing or hardening of arteries causes the death of brain tissue. Symptoms will depend on what part of the brain tissue is destroyed. These symptoms usually come on suddenly.

Other common causes are as follows:

  • Creutzfeldt-Jakob disease, a degenerative disorder of the nervous system that progresses quickly and causes problems with walking, talking, and the senses. When dementia occurs in young or middle-aged people, it is often due to this disease.
  • Huntington disease, a progressive disease causing brain cells to waste away that affects both the body and the mind. It causes changes in thinking, memory, speech, judgment, and personality. Dementia often occurs in the later stages of the disease. Huntingdon Disease has been linked to a certain gene that a person can inherit.
  • Lewy body disease, a degenerative disease of the nervous system. Lewy bodies are deposits of protein in nerve cells, often deep within the brains of those who also have Parkinson Disease. When these protein deposits occur throughout the brain, dementia results. The course of illness is different from Alzheimer's disease, in that it results in changes in the speed of thought, memory, judgment, reasoning, and language. It can also cause a person to get lost easily. In addition, it may cause hallucinations.
  • Parkinson's disease, a degenerative disorder of part of the nervous system. Up to 30 to 40 percent of people with this disease may develop dementia in the later stages.
  • Pick disease, also known as frontotemporal dementia, or FTD. FTD is a rare disorder of the brain. It causes changes in personality, behavior, and memory over time. It gets steadily worse, but it hard to diagnose until after death.
  • Other less common disorders that can cause dementia, or dementia-like behaviors include:

  • brain tumor
  • chronic subdural hematoma, a bleeding between the brain lining and brain tissue
  • HIV, the immunodeficiency disorder that leads to AIDS
  • multiple sclerosis, a disorder of the sheath that lines the brain and spinal cord
  • neurosyphilis, an infection of the nervous system by the syphilis bacterium, which causes weakness and mental deterioration
  • normal pressure hydrocephalus, which is a build up of cerebrospinal fluid in the brain. This condition can often be treated through surgery to put a shunt tube in the brain that allows the excess fluid to flow out of the brain.
  • progressive supranuclear palsy, also known as Steele-Richardson-Olszewski syndrome, a rare disorder of late middle age that causes widespread nervous system problems
  • stroke
  • viral or bacterial encephalitis, a swelling of the brain
  • Wilson disease, a rare disease causing an excess of copper in the liver, brain, kidneys, and corneas
  • Certain abnormal aspects of a person's metabolism or hormones may also be responsible for the development of dementia, including the following:

  • chronic alcohol abuse
  • chronic exposure to metals, such as lead or mercury, and to dyes, such as aniline
  • high-dose steroid abuse
  • hyperthyroidism, which means the thyroid gland is overactive
  • hypothyroidism, which means the thyroid gland is underactive
  • low body levels of vitamin B12
  • medicine side effects or drug interactions
  • thiamine deficiency
  • too little niacin, which is vitamin B3
  • In some of these cases, dementia can be reversed by removing the toxic agent or bringing vitamin levels back to a healthy range.

    In older adults, depression and dementia are often mistaken for each other. They do sometimes occur together, but depression is treatable, while dementia is not.


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    Dementia: Symptoms & Signs

    Author: Ann Reyes, Ph.D.
    Reviewer: Kathleen A. MacNaughton, RN, BSN
    Date Reviewed: 10/10/02

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