ALZHEIMER'S DISEASE (AD)

Alzheimer's disease is the most common cause of dementia and accounts for 50% - 60% of all cases. It destroys brain cells and nerves disrupting the transmitters which carry messages in the brain, particularly those responsible for storing memories. AD was first described by the German neurologist Alois Alzheimer in 1907. He wrote of a physical disease in which brain cells are destroyed. The appearance of this destruction is referred to as "plaques and tangles".

During the course of Alzheimer's disease, nerve cells die in particular regions of the brain. The brain shrinks as gaps develop in the temporal lobe and hippocampus, which are responsible for storing and retrieving new information. This in turn affects people's ability to remember, speak, think and make decisions. The production of certain chemicals in the brain, such as acetylcholine is also affected. It is not known what causes nerve cells to die but there are characteristic appearances of the brain after death. In particular, 'tangles' and 'plaques' made from protein fragments are observed under the microscope in damaged areas of brain. This confirms the diagnosis of Alzheimer's disease.

The onset of the disease is usually quite gradual. Likewise, symptoms appear gradually, but progressively worsen as the disease spreads. Typically, Alzheimer's disease begins with lapses of memory, difficulty in finding the right words for everyday objects or mood swings. As Alzheimer's progresses, the person may:

In advanced cases people may also:

Alzheimer's disease is a physical disease, not a mental disorder. The brain controls everything we think, say, feel and do. So when the brain becomes diseased, our thoughts, abilities and behaviours are all affected.

The symptoms of Alzheimer's disease are often mistaken as just a normal part of getting older. Many of us feel that as we age we forget things more easily. But the forgetfulness of old age is vastly different to the memory loss of Alzheimer's disease.

VASCULAR DEMENTIA

Vascular dementia accounts for about 20% of all cases of dementia.Vascular disease occurs where blood vessels are damaged and the supply of oxygen is at risk. If oxygen supply fails in the brain, brain cells are likely to die leading to a series of mini strokes (infarcts) and possible vascular dementia.

The mini strokes that cause vascular dementia are often so slight that they cause no immediate symptoms, or they may cause some temporary confusion. However, each stroke destroys a small area of cells in the brain by cutting off its blood supply and the cumulative effect of a number of mini strokes is often sufficient to cause vascular dementia. Vascular dementia and Alzheimer's disease frequently occur together and they may often act in combination to cause dementia.

With vascular dementia, a mental decline is likely to have a clear start date and symptoms tend to progress in a series of steps following each attack, suggesting that small strokes have been occurring. Symptoms may include severe depression, mood swings and epilepsy. Some areas of the brain may be more affected than others. Consequently, some mental abilities may be relatively unaffected.

DEMENTIA WITH LEWY BODIES

Dementia with Lewy bodies is the third most common cause of dementia and may occur in up to 20% of cases confirmed at autopsy. Dementia with Lewy bodies is similar to Alzheimer's disease in that it is caused by the degeneration and death of nerve cells in the brain. It takes its name from the abnormal collections of protein, known as Lewy bodies, which occur in the nerve cells of the brain.

Half or more of people with Lewy body disease also develop signs and symptoms of Parkinson's disease. People with Lewy body disease are very sensitive to some tranquillisers known as antipsychotic or neuroleptic drugs and their use should be avoided if at all possible.

Dementia with Lewy body affects:

FRONTO-TEMPORAL DEMENTIA'S (INCLUDING PICK'S DISEASE)

Fronto-temporal dementias are a relatively rare cause of dementia and typically develop at an earlier age than Alzheimer's disease, usually in a person in their forties or fifties. The frontal lobe of the brain is particularly affected in early stages.

Frontal lobe dementia is caused in a similar way to Alzheimer's disease in that it involves a progressive decline in a person's mental abilities over a number of years. Damage to brain cells is more localised than in Alzheimer's disease and usually begins in the frontal lobe part of the brain.

The frontal lobe of the brain governs people's mood and behaviour. The person's mood and behaviour may become fixed and difficult to change, making them appear selfish and unfeeling. A person with this type of dementia does not usually have sudden lapses of memory which are characteristic of Alzheimer's disease.

ALCOHOL-RELATED DEMENTIA (INCLUDING KORSAKOFF'S SYNDROME)

People who drink too much alcohol do seem to be at risk of developing problems with their memory. Some have a specific problem of loss of short-term memory known as Korsakoff's syndrome which develops because of vitamin B1 deficiency. Others develop a wider range of problems that resemble Alzheimer's disease.

AIDS-RELATED DEMENTIA

HIV, the virus which leads to AIDS, can be a cause of dementia. The virus has been found in the brain of people with HIV as early as two days after initial infection. This condition is usually referred to as AIDS dementia complex (ADC).