Causes

The causes of dementia are still not yet fully understood. More research is urgently needed to increase our understanding since this knowledge offers the best chance to develop ways of halting or preventing the condition.

Research into the causes of dementia has so far shown that:

Alzheimer's disease

The symptoms are caused by nerve cells dying in certain areas of the brain and the deterioration of millions of connections between affected nerve cells. The loss of connections in the part of the brain dealing with memory usually causes the first symptoms. The disease progresses and spreads, gradually affecting cells in other parts of the brain. More research is needed to find out what causes the nerve cells to die. Different types of protein deposits, known as amyloid plaques and tau tangles, accumulate in the brains of Alzheimer's patients, but it is not yet known whether these actually cause the disease or are a symptom of it.

Lewy Body disease

Lewy Bodies are small deposits of protein found inside the nerve cells in the brains of people diagnosed with this disease. They alter the way the brain functions and in particular the way chemical messengers work within the brain. The affected nerve cells are found in an area of the brain called the cerebral cortex.

Vascular dementia

Vascular dementia describes a number of conditions that are linked by vascular causes, such as sustained high blood pressure (hypertension), stroke and atrial fibrillation. When the condition is caused by a series of repeated small strokes, it is known as multi-infarct dementia. During a stroke, parts of the brain are deprived of blood, which carries oxygen and nutrients, and so they die. These damaged areas of the brain are known as vascular brain lesions and can sometimes be seen on a CT scan.

Fronto-temporal dementia

There are none of the plaques or tangles seen in Alzheimer's disease and the damage to brain cells is more localised. There are several different types of fronto-temporal dementia:

Pick's disease symptoms are caused by abnormal and swollen brain cells, known as Pick's cells, and abnormal protein deposits within cells, known as Pick bodies. The disease mostly affects the frontal and temporal lobes of the brain.

Primary progressive aphasia causes a loss of cells in areas of the brain's frontal lobe that govern speech. It is difficult to distinguish from Pick's disease in living patients.

Frontal lobe degeneration mainly affects those parts of the brain that govern social behaviour. The onset of the disease is usually slow.