This column is the first in a series that will focus on the dementing illnesses, their nursing management, and current research. Because of past confusion about definitions, I will devote this column to defining the terms in current use.
Although dramatic intellectual decline occurring in old age has been recognized for at least 3,000 years, it has been assumed for too long to be the inevitable result of longevity. As such, it attracted little research attention.
In the 1960s, Sir Martin Roth and his coworkers made two important observations in studies done in Great Britain: 1) the pathologic changes in the brain of people dying after 65 from senile dementia was the same as had been described in younger ("presenile") victims of Alzheimer's disease, and 2) only about 5% of those over 60 and 20% of those over 80 developed symptoms of dementia. These observations indentified "senility" in the old as a disease process and not as an inevitable characteristic of aging, making it an appropriate focus for research.
Dementia is now recognized to be a syndrome. Unlike the previously used term "chronic organic brain syndrome," the word does not imply chronicity or ir reversibility. In fact, of the 60 or more diseases that may cause dementia, some are treatable, making a thorough search for treatable causes well worthwhile.
Dementia is defined as "a global decline from previous intellectual function occuring in clear consciousness." This differentiates it from "delirium," which occurs in clouded consciousness, from mental retardation, and from conditions in which only one area of intellectual function (for example, speech or memory) is impaired.
Of the diseases causing a dementia syndrome, two - Alzheimer's disease (also termed senile dementia of the Alzheimer's type or SDAT) and multiinfarct dementia - account for approximately 90% of the cases seen. Many other diseases including depression, Parkinson's disease, Huntington's disease, vitamin B-12 deficiency, thyroid disease, and normal pressure hydrocephalus also can cause dementia.
Multi-infarct dementia is characterized by a stair-step progression, focal neurologic findings, and a personal or family history of risk factors such as heart disease, diabetes, or hypertension. It is a potentially preventable disease if the cause of the stroke (for example, emboli from a valvular or carotid lesion) can be treated.
A diagnosis of Alzheimer's disease is made after thorough examination has ruled out all other possible causes and upon a history of a gradually progressive course. A definitive diagnosis can be made only upon examination of brain tissue, currently only done at autopsy.