Encyclopedia / D / Dementia



Dementia is a permanent decline in cognitive function and memory from a previous level of function.


Dementia is a brain disorder with permanent loss of memory or other higher cognitive function.. Dementia can either be progressive, such as in Alzheimer's disease, or may remain stable, as can be seen after a stroke or head injury. Different types of dementia can affect various cognitive functions such as memory, personality, or executive function.

By definition, dementia is permanent. A brief change in cognitive function is more often called a "delirium". Different types of dementia can affect different abilities. Some patients may get lost, have trouble remembering things, become unable to remember names of objects and people, or have trouble calculating numbers, among other problems.

In many cases, dementia may progress very slowly and it is difficult to determine when the problem precisely began. In some cases, such as when a patient has a stroke, the beginning is very sudden and noticeable.


Physicians generally recognize two broad categories of dementia:

Primary dementias are those like Alzheimer's in which the dementia itself is the major sign of an organic brain disease not directly related to any other organic illness.

Secondary dementias are those caused by, or closely related to, some other recognizable disease - such as AIDS, head injury, stroke, multiple sclerosis, or one of numerous other identifiable mental conditions.

Pseudodementia is another category of dementia that, as the name implies, is not a true dementia but rather a set of similar symptoms that mimic the condition, often seen in patients with depression.


All dementias - whether primary or secondary, treatable or untreatable - share a few clinical characteristics in common. Loss of memory and inability to perform routine tasks - such as losing one's way in the neighborhood, difficulties in job performance, language problems - are particularly common.

The most recent memories are lost sooner than older ones, and new memories, perhaps of something that happened minutes earlier, are difficult to retain. For example, a woman might ask her husband when they are scheduled to visit their children. "Saturday," he might reply. Just minutes later, she might ask the identical question. In the early stages of the dementia, however, she probably will have no difficulty identifying photos of the children, or even of casual friends, taken 30 years earlier.

In certain forms of dementia, behavioral changes (such as increased aggressiveness), may be prominent.

As the disease progresses, patients lose the ability to function independently and become increasingly disoriented to time and place. Wandering may become a significant problem. Patients become unable to care for themselves and grooming and dressing standards deteriorate rapidly. Patients often dress inappropriately for the season and confuse underwear with outer garments.

In the progressive dementias, recent memory, retention and attention span deteriorate steadily. Language skills, particularly ability to name objects (anomia) or generate a word list decline until a patient can no longer use full sentences.


The diagnosis of dementia is based upon a good clinical history and an examination to determine the nature of the organic or non-organic cause of mental confusion. Often, a physician may perform a simple group of memory tests called the "mini mental status examination". In some cases, special neuropsychological testing may be necessary to confirm dementia, as opposed to effects of normal aging. Blood work and a picture of the brain (CAT scan or MRI) are useful to exclude any treatable condition.


In some cases, blood tests or imaging studies may reveal a condition responsible for the cognitive decline. Disorders such as vitamin deficiency, infection, or hydrocephalus can be treated with specific therapies that can reverse the symptoms in some cases.

In most of the progressive dementias, such as Alzheimer's disease, a specific cure is lacking. However, there are several agents available which have been proven to slow the progression of cognitive decline. These agents also enable patients to maintain their independence for a longer period of time. These medications also reduce burden on the caregiver. However, these drugs do not stop the progressive nature of the disorder and patients eventually decline further.


What is the cause of the dementia?

Is the dementia secondary to some other disease?

Is the person with dementia safe to be left alone or is supervision always necessary?

What medications or other therapy may help improve function?

What treatments are available?

How can we best cope?

What is the prognosis - what can we expect?