Dementia

Dementia, itself, neither implies a specific disease nor implies a specific underlying pathology. It refers to a change in cognitive function that is severe enough to compromise an individual's daily function. The Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV) defines dementia as an acquired impairment of cognitive function that includes a decline in memory beyond what would be expected for age and at least one other cognitive function, such as attention, visuospatial skills or language, or a decline in executive functioning such as planning, organization, sequencing, or abstracting. The decline cannot only affect emotional abilities, but must also interfere with work or social activities. The deficits should not be accompanied by an impairment of arousal (delirium) or be accounted for by another psychiatric condition, such as depression or schizophrenia. Dementia can further be defined by a possible, probable, or definite etiologic diagnosis. A degenerative dementia implies disease progression over time.

While the DSM-IV criteria are generally useful, one problem with the criteria is that memory impairment is an essential feature. While this is common in most dementias, other dementias may present with impairment in a non-memory cognitive domain. If the initial presentation is a change in personality or behavior, rather than memory, a frontotemporal dementia may be the diagnosis. In subjects with parkinsonism, hallucinations and fluctuations in behavior, dementia with Lewy bodies may be more likely than AD.