Dementia is a deterioration of mental condition. Dementia usually occurs in later life, though rarer cases of presenile dementia are diagnosed. Terms that are used synonymously with dementia are chronic brain syndrome, organic mental syndrome, and senile confusional state.
The incidence of dementia is less than 10% of persons over age 65 but perhaps a quarter of those over age 80 and half of all nursing home patients. Dementia is not the most common mental disorder in later life (that is depression), nor should it be considered an inevitable concomitant of aging. Many individuals are able to preserve cognitive functioning into their ninth decade.
The onset of most cases of dementia tends to be gradual. The first mental changes may be heightened rigidity, suspiciousness, crankiness, or depression. As the disorder progresses, deficits in short-term memory become pronounced. Patients may be able to recall in great detail what happened years ago but be unable to remember the answers to a question given five minutes ago. One woman in a nursing home could remember how to play a song she had learned in a Prohibition-era honky tonk, but when the other residents applauded and asked for another song, she played it again. The ability to follow instructions also decreases, leading to the consternation of the patient's caregivers. Disorientation in time develops: the patient does not know which day of the week it is. Then comes disorientation in place: the patient may get lost, even in familiar territory. The patient may develop aphasias, apraxias, perseveration, and/or social withdrawal. In later stages the recognition of significant others may be lost, along with bowel and bladder functions. Death usually occurs when the patient loses the ability to swallow.
Dementia is different in kind rather than degree from the forgetfulness of which most elders complain. Benign senescent forgetfulness is an age-associated memory impairment that does not have a serious prognostic implication. Neither is dementia analogous to a second childhood. Childish playfulness stems from a lack of knowledge about proper adult roles, whereas demented elders may manifest such behavior because of impaired memory, confusion, or sensory/motor limitations. Some nursing home patients may act more like children if the staff rewards such behavior with attention, especially affection.
More than 50 different diseases can bring about dementia. Huntington's chorea is due entirely to the presence of a single dominant gene. Creutzfeld-Jakob disease is caused by viral infection, perhaps due to the consumption of insufficiently cooked bovine brain. Kuru, a viral infection in Melanesia, may be spread by ritual cannibalism. Hydrocephalus is excessive pressure of cerebrospinal fluid in the ventricles, impairing the functioning of the cortex. Chronic alcohol abuse, tertiary syphilis (general paresis), AIDS, encephalitis, subdural hemotoma, Parkinson's Disease, intracranial neoplasm, head trauma, and meningitis are other possible causes.
The majority of the demented geriatric patients suffer from Alzheimer's Disease (also known as senile dementia of the Alzheimer type), which results in specific degenerative diseases in the brain's tissues. A similar though rarer disorder is Pick's disease, which usually affects people in their fifties and is located primarily in the frontal and temporal lobes. These changes can be observed postmortem or via computerized tomography.
Before 1980 it was assumed that the principal cause of dementia is cerebral arteriosclerosis, a hardening of the brain's arteries that results in less oxygen being supplied to the brain's tissues. The current consensus is that diminished blood flow is a significant causal factor in only a minority of dementia cases of later life. Reduced oxygen may be more a symptom of reduced cortical functioning rather than its cause. A greater cause of dementia posed by the vascular system may be multi-infarct dementia-many tiny strokes that have the combined impact of diminishing cognitive ability without bringing on the paralysis characteristic of the larger strokes.
The diagnosis of dementia cannot be based solely upon the patient's complaints of a failing memory. There is no correlation between the self-reported memory capacity and memory capacity as indicated by objective tests. Many of the elders who complain the most about diminishing memory are well within the normal range but suffer from depression. Some thoroughly demented patients perceive no difficulty with their memories.
The first step should be brief psychological screening tests. Use of the Bender-Gestalt, Intelligence Quotient test scales, or other tests devised for other purposes or other age groups should be avoided. Questions that test the capacity for orientation in space and time are useful. The ability to draw a clock face with its hands and dial is useful. Focusing the examination on short-term memory tends to neutralize some of the confounding variables and give a truer indication of dementia. Many of these tests (e.g., the Mental Status Questionnaire or the Folstein Mini Mental Status Exam) have a greater sensitivity than specificity: it is more likely that some normal elders will be misdiagnosed as having dementia than that seniles will score in the normal range. Whenever these screening tests suggest the presence of dementia, a comprehensive neurological examination is appropriate.
One diagnostic difficulty is to distinguish organically based dementia from a pseudodementia due to depression. Dementia is usually characterized by a gradual onset, while depression may have a rapid progression of symptoms in the wake of environmental stress or loss. Depressed patients are more likely to complain of memory loss and give "don't know" answers. Purely demented patients are more likely to attempt to conceal cognitive deficits or to give ludicrous answers rather than admit that they do not know the answer. One complication for the differential diagnosis of depression is that self-rating scales (e.g., the Geriatric Depression Scale) may lose their validity as senile confusion increases: the patient may be unable to understand the questions. Another problem with differential diagnosis is that the two disorders are not mutually exclusive. Awareness of cognitive decline can produce a depressive reaction, and a sizable minority of early-stage dementia patients develop a clinically significant depression.
Another possibility is that the cognitive impairments are the result of a delirium or an amnestic disorder rather than dementia. This may be the case with many confused elders admitted to general hospitals. What is needed is a knowledge of the details about the onset, course, and laboratory testing. The complicating factors are that delirious patients cannot take memory tests and these disorders are not mutually exclusive.
Even with computerized tomography and spinal taps, the diagnosis of dementia is far from exact. Some patients are falsely labeled as demented, while other cases might go unnoticed until autopsy.
Treatment for dementia can be both medical and psychosocial. About a fifth of dementia patients have a treatable organic cause (e.g., hydrocephalus, which is treatable by surgery). The use of medications has been much debated. While some patients report some benefit from tacrine or Hydergine, some report side effects from the former and most report little benefit from the latter. Another controversial issue is the use of psychiatric medications (e.g., antidepressants, antipsychotics) with dementia patients. In many nursing homes the antidepressants are probably underutilized while the antipsychotics are often given to diminish behaviors that the staff may find objectionable or inconvenient.