Dementia: when is it not Alzheimer disease?

The advent of symptomatic therapies for Alzheimer disease has placed increasing emphasis on early diagnosis of the dementia syndrome and its various types. This article reviews the definition and epidemiology of the condition that affects up to 50% of all Americans over the age of 80. Also discussed are the main causes of dementia, focusing on those that are not Alzheimer disease and a diagnostic approach that is based on guidelines recently published by the American Academy of Neurology.