Alzheimer's disease. Coloured computed tomography (CT) scan of an axial (horizontal) section through the brain of a patient suffering from Alzheimer's disease. This condition causes widespread destruction (brown) of brain tissue (green), leading to shrinkage of the brain. This results in progressive memory loss and disorientation. Alzheimer's is the most common cause of senile dementia. There is no known cause and no cure. CT scans use X-rays to construct images of slices through parts of the body.