痴呆の基本的な診かた

Dementia is characterized by an acquired and generalized impairement of cognitive function that interferes with daily and social activities with no disturbance of consciousness. This disorder is becoming progressively more common. However, it is not easy to diagnose and treat it. The patients with dementia are often not aware of their problems well. Therefore, the history should be obtained from family members or other informants, in addition to interviewing the patients with cognitive decline. The clinician needs to take the history sufficiently and also get information about the conditions of family such as their availability and ability to help. The mode of onset and time course of deterioration are specially important in differential diagnosis. Whether the patient has dementia is determined by the history, degree of cognitive dysfunction on mental state examination, general physical examination including neurological assessment, and laboratory investigations. Dementia should be carefully differentiated from delirium, depressive disorder, and the other psychotic disorders. The history is most useful in distinguishing dementia from the others. The onset of delirium is rapid, while that of dementia is usually slow. The symptoms of delirium tend to fluctuate and often become worse at night. But dementia and delirium frequently coexit, and the differentiation may be difficult in this case. In depressive disorder, usually a history of mood disturbance precedes the other symptoms. Patients with depression typically respond not incorrectly but incompletely to questions, for example, "I don't know". Some types of dementia are reversible or remediable. Therefore, it is most important not to miss any treatable dementia, such as subdural hematoma and normal pressure hydrocephalus. Vascular dementia and Alzheimer's disease are predominant types of dementia among the elderly. It is also important to differentiate these two diseases for proper treatment and care.