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How is it diagnosed?

Alzheimer's disease and Alzheimer's dementia


Alzheimer's disease is a cause 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 dementia. 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.

A carer 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.

The importance of a timely diagnosis

Although it is not possible to accurately predict dementia, it is extremely important that people who have dementia obtain a timely diagnosis. It is only by obtaining a diagnosis that the correct medical treatment can be prescribed. Delayed diagnosis prevents people from benefiting from the latest medical advances, which in many cases lead to a temporary improvement of symptoms.

However, memory problems are not always a sign of dementia. Although mental faculties change with age, ageing is not synonymous with dementia. Many older people need more time to assimilate information and this may affect their capacity to learn and remember things. Nevertheless, older people are often worried about these changes and are afraid that they might be developing dementia.

At the same time, many people do not know what the symptoms are. This is not surprising, as different kinds of dementia have different symptoms. Furthermore, some forms of dementia (e.g. due to Alzheimer's disease) are insidious. The following table describes some of the early symptoms of different kinds of dementia.

Alzheimer's dementia

  • Difficulties with memory and orientation
  • Difficulty finding one's words
  • Personality change
  • Lack of interest in hobbies

Vascular dementia

  • Slowing down of thought and movement

Pick's disease and frontal lobe degeneration

  • Loss of control and inhibitions
  • Personality change
  • Difficulties with language

Dementia with Lewy Bodies

  • Cognitive decline
  • Similar symptoms to those of Parkinson's disease
  • Visual hallucinations

Creutzfeld-Jacob Disease

  • Odd lapses of memory and mood swings
  • Lack of co-ordination
  • Inclination to withdraw from social activities
  • Attention difficulties (very rapid progression usually)

The presence of one or more of these symptoms does not necessarily mean that a person has dementia. In fact, in the case of older people, the symptoms of depression are very similar to those observed in the early stages of dementia and it is not uncommon for the two to be mixed up. Sometimes, the symptoms are linked to other disorders such as thyroid gland dysfunction, lack of vitamin B12, disorders of the metabolic system, alcohol or drug abuse, infections, surgical operations, stress and intolerance of medication. In such cases, the symptoms may be reversible.

A differential diagnosis is clearly essential in order to rule out other causes for the symptoms experienced and correctly diagnose dementia. In case of concern, the family doctor/general practitioner should be consulted. He or she will carry out a few tests and if his/her suspicions are confirmed refer the person concerned to the relevant specialists for further tests.

Should the person be informed of their diagnosis?

Nowadays more and more people with Alzheimer's disease are being informed of their diagnosis. Some people might not want to be informed of the diagnosis. However, it is generally considered that everyone should have the right to be informed and be given the opportunity to decide whether they would rather know or waive this right. 

Sometimes, a diagnosis is made as a result of concerns expressed by relatives. The person with dementia might not be unaware or does not agree that they have any difficulties. 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 dementia 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. However, it is important to be sensitive to people's needs and wishes with regard to whether and if so how the disclosure of a diagnosis is made. 



Last Updated: Tuesday 18 June 2019