Magnetic resonance imaging of the ageing brain.

Many changes occur in the brain with normal ageing. These have been extensively investigated by autopsy studies and more recently with high resolution MRI. Dementia is a major public health problem worldwide which affects the elderly population. Magnetic resonance imaging (MRI) is the imaging test of choice to identify underlying treatable causes of dementia, including normal pressure hydrocephalus, subdural haematoma and intracranial tumour. It is important to understand the normal changes which occur with ageing and these should not be interpreted as pathological lesions on MRI. Though there is considerable overlap between findings of normal and abnormal ageing brain, with a good clinical background, it is possible, in many cases, to suggest the diagnosis of Alzheimer's disease, multi-infarct dementia and various other pathological processes.