Alzheimer's disease accounts for more than half of dementia cases. It destroys cells, disrupting transmitters that carry messages in the brain, particularly those responsible for storing memories. Click for more information about Alzheimer's disease. Vascular disease or stroke causes 20 per cent of cases. Arteries which supply blood to the brain become blocked.
Brain tissue is damaged due to lack of oxygen or from strokes causing bleeding into the brain.
Lewy body disease, frontal lobe dementia and Pick s disease all lead to the destruction of brain cells. Parkinson's disease is associated with dementia in 15 to 20 per cent of cases, and later stages of Huntington's disease also involve mental deterioration. Brain tumour or pressure in the head can cause symptoms of dementia. A cure is sometimes possible by removing the tumour. The symptoms of severe depression are sometimes mistaken for dementia, but diminish if the depression is treated.