The diagnosis of dementia is a clinical one that can only be made with the rigorous use of clearly defined diagnostic criteria in an interview setting. The diagnosis cannot be made by laboratory tests or imaging techniques alone. In the elderly, a number of other psychiatric syndromes must be distinguished from dementia, including delirium, psychosis, depression, and mania. Sometimes it is not possible to make this distinction with confidence. Most dementias are caused by Alzheimer's disease or multi-infarct dementia, and the probable etiologic diagnosis can be made fairly quickly. However, a number of etiologies are possible, and some patients require extensive study. Some uncertainty is usual in the diagnosis of the living patient because routine brain biopsy is not feasible. Geropsychiatric and neurologic consultants can be helpful in selected cases.
