The Principle Syndromes of Dementia

Dementia is a syndrome defined by a subacute or insidious decline in cognition from a previously higher level. Dementia, in contrast to disorders defined by deficits in only one cognitive or behavioral domain, is diagnosed when there are deficits in multiple domains. In addition to memory dysfunction, cognitive and behavioral manifestations of the dementia syndrome also include abnormalities in speech/language, visuo-spatial function, abstract reasoning/executive function, and mood/personality. Alzheimer's disease (AD) is the most common cause of dementia in the elderly. As a consequence, memory dysfunction in the form of frequent repeating of questions, forgetting of recent events and conversations, and misplacing of items are the most common symptoms of dementia that clinicians are likely to encounter. This chapter discusses the presentation, symptoms, stages, epidemiology, and genetics of AD, dementias associated with stroke, dementia with extrapyramidal features, Creutzfeldt-Jakob disease, and fronto-temporal dementia.