Dementia and disorders of cognition

Dementia is a progressive deterioration in cognitive function caused by degenerative brain disease. It is one of the most common presentations encountered in general medical practice, especially in elderly individuals. Dementia is a syndrome that can be caused by different types of brain pathology including, commonly, Alzheimer's disease and brain vascular disease. Different pathologies have different ‘signatures', especially at an early stage, based on combinations of cognitive, behavioural and neurological features. We describe common examples here, in addition to less common causes that must not be missed because they are treatable. Brain imaging and biochemical tests on blood and cerebrospinal fluid (‘biomarkers’) are increasingly contributing to the accurate early diagnosis of dementia types, especially Alzheimer's disease. These will potentially facilitate the early use of new specific treatments for Alzheimer's disease that are being evaluated, as well as help families to confront the problem early.