Dementia is among the most common and disabling of diseases and places a huge burden on carers and families as well as on social and medical services. Its prevalence rises from about 1.4% of adults aged between 65–70 years to 23.6% of those over 85. The number of patients with dementia is predicted to increase steeply as the proportion of people surviving well in to old age continues to rise. The annual economic cost is estimated at £7 billion per annum in the UK and over $100 billion in the USA.

Accurate diagnosis of most diseases that cause dementia depends on post-mortem neuropathological examination. In this review, I shall cover some of the practical issues involved in the post-mortem investigation of dementia and describe the principal abnormalities in the more common diseases that are responsible. This is not an exhaustive review of the neuropathology of dementia, which is well covered in many large reference books and is beyond the scope of the present text.

WHY BOTHER EXAMINING THE BRAIN POST MORTEM?

In most published series, the accuracy of clinical diagnosis of the different diseases that cause dementia is of the order of 70–80%. Establishing a precise diagnosis by post-mortem neuropathological examination will not, of course, benefit the individual patient but matters nonetheless, for several reasons:

• With rare exceptions, brain tissue from patients with dementia cannot be obtained for diagnosis except post mortem.

• The post-mortem examination yields accurate epidemiological data and is an important means of auditing and assuring the quality of clinical care.

• The findings help to educate clinicians, and the post-mortem diagnostic process to train pathologists.

• Many neurodegenerative diseases are inherited or are associated with specific genetic risk factors (table 1). Accurate diagnosis is important for assessing the risk to other members of the family.

• This is a field in which improvements in understanding of disease …