Alzheimer's disease is a form of dementia but is not necessarily caused by the same factors which cause other forms of dementia. However, despite a considerable amount of research, the actual cause of the disease remains unknown. There is no single test to determine whether someone has Alzheimer's disease. It is diagnosed by a process of elimination, as well as a careful examination of a person's physical and mental state, rather than by finding actual evidence of the disease.

Physical and mental state:
A caregiver or relative may be asked to provide information about the person's behaviour,e.g. difficulties getting dressed, washing, handling finances, keeping appointments, travelling alone, managing at work and using household appliances. A neuropsychological assessment is usually carried out. This involves finding out about possible problems with memory, language, planning and attention. A simple test called the Mini-Mental State Examination is often used. This involves the person being asked to answer questions such as: What is the date? What city are we in? What is this called? (shown a watch). Another part of the test is to follow a series of simple instructions.

A number of tests may be carried out (e.g. blood and urine samples) in order to rule out the possibility of other illnesses which might explain the dementia syndrome or illnesses which might aggravate an already existing case of Alzheimer's disease. In addition to this, a few methods of brain imaging have been developed which produce images of the living brain,thereby revealing possible differences between the brains of people with Alzheimer's disease and those of non-affected individuals. These tests provide a risk-free and pain-free means of examining the brain of a living person. Although they cannot lead to a certain diagnosis of Alzheimer's disease, some doctors may use one or more of these techniques to give more weight to a diagnosis.

Methods of brain imaging:
Magnetic Resonance Imaging. This permits an extremely detailed image of the brain's structure. When one image is placed over another, taken a few months' later, it is possible to see changes at an early stage in a certain part of the brain. CT (Computed Tomography) scanning: This measures the thickness of a part of the brain which becomes rapidly thinner in people with Alzheimer's disease. SPECT: Single Photon Emission Computed Tomography) Scanning. This can be used to measure the flow of blood in the brain, which has been found to be reduced in people with Alzheimer's disease as a consequence of nerve cells not working properly.

PET: (Positron Emission Tomography)
The use of this scanning technique is often limited to research settings. It can detect changes in the way the brain of someone with Alzheimer's disease functions. It can, for example, detect abnormal patterns of glucose usage by the brain.

What are the different kinds of diagnosis?

There are three possibilities for a diagnosis of Alzheimer's disease : possible, probable and certain Alzheimer's disease. Possible alzheimer's disease. A diagnosis of possible Alzheimer's disease is based on the observation of clinical symptoms and the deterioration of two or more cognitive functions (e.g. memory, language or thought) when a second illness is present which is not considered to be the cause of dementia, but makes the diagnosis of Alzheimer's disease less certain. Probable Alzheimer's disease. The diagnosis is classed as probable on the basis of the same criteria used to diagnose possible Alzheimer's disease, but in the absence of a second illness. Certain Alzheimer's disease. Identification of characteristic plaques and tangles in the brain is the only way to confirm with certainty the diagnosis of Alzheimer's disease. For this reason, the third diagnosis, that of certain Alzheimer's disease, can only be made by brain biopsy or after an autopsy has been carried out. Should the person be informed of their diagnosis?

Nowadays more and more people with Alzheimer's disease are being informed of their diagnosis. This is perhaps due to a greater awareness of the disease. Some people might not want to be informed of the diagnosis. However, it is generally considered that everyone should havethe right and be given the opportunity to decide whether they would rather know or waive this right. There are pros and cons involved in informing someone of their diagnosis. Also once the decision has been made to inform someone about their diagnosis the problem may arise of how to inform the person.

Pros and cons of telling the person:
In many cases a diagnosis is made as a result of concern expressed by members of the family. Often the person with dementia is unaware or does not agree that they have a problem. They are therefore not interested in obtaining a diagnosis. Some might feel depressed about knowing or feel that they would have been happier not knowing.

However, there are many advantages to knowing. When a person knows that they have Alzheimer's disease and understands what it involves, they can plan how to make the most of the remaining years of relative unimpaired mental functioning. They can also take an active role in planning their care, arrange who will care for them, make important financial decisions and even decide to participate in research or make the necessary arrangements to donate brain tissue after their death for research.

How to inform the person of the diagnosis:
Some relatives and friends may find it difficult to approach the subject. Some people would prefer to be told privately on a one-to-one basis, whereas others might find it more reassuring to be told in the presence of their family, who could give them moral and emotional support.

Another possibility is to arrange for the person's doctor to tell them. It might help to arrange to go to the doctor together or for the person to go alone. The doctor could then answer any questions that either the caregiver and/or the person with dementia might have.

The way the diagnosis is explained will depend on the person's ability to understand. Some people might understand an explanation of what the disease is, how it tends to progress and the consequences for daily living, whereas others might only be able to grasp that they have a disease which involves the loss of memory.

Once informed, they may need support to come to terms with feelings of anger, self-blame, fear and depression. Some might be able to benefit from counselling and support groups, provided that the disease is not too far advanced.

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