In this chapter, the assessment of dementia is addressed with the use of three questions:

1. Why? What is the purpose of the assessment?
   
2. What exactly are you assessing?
   
3. How do you go about gathering the information you need in order to make a diagnosis?

Before commencing an assessment with a person with possible dementia, it is important to consider the question of why you are doing it. It is worth stating the obvious here; the reason we assess an individual is in the hope that it will be helpful to that person in some way. This may be directly helpful, that is, clarifying the diagnosis to a person with concerns about memory. Or benefits of an assessment may be more indirect; it can be valuable to professionals or family members to know about the diagnosis in order to better understand the condition or make the best plans for care.

In the past decade, society has moved away from the belief that a diagnosis of dementia is unimportant, to one where making a diagnosis is viewed unquestioningly as a good thing. This complete about turn has led to considerable pressure to increase diagnosis rates as though this is an end in itself. It is not.

We should also be mindful that like any health care intervention, dementia assessment has the potential to do harm. Proper consideration should also be given to informed consent. In the case of an individual lacking the mental capacity to consent, the assessment must be in that person’s best interests.

A health assessment may have many different components (see Box 3.1). We may be interested in finding out if the person has a clinical syndrome of dementia. If so, we may want more detail, for example, how severe is it, or what is the likely disease process that is causing the dementia? From a practical point of view, it may be valuable to understand the pattern of cognitive losses and preserved skills, to aid understanding and care planning.

If we are to help a person live well with dementia, we may be more interested in the sources of support, who the carers are and how the carers/family may be feeling. Is there any risk arising from the dementia? If there are important decisions to be made, does the person have the capacity to make these decisions?

The exact nature of the assessment will be determined by its purpose. If the aim is to make a diagnosis of dementia and also to clarify the underlying brain disease, the assessment is essentially a three-piece jigsaw puzzle consisting of a clinical history, cognitive testing and imaging. Of these, the history is by far the most important, with cognitive testing and imaging providing useful supportive information (Box 10.2).

A good description of change in mental skills is where assessment starts (see Box 10.3). The extent to which the person can contribute to the assessment process will depend on the severity or type of dementia. Most people with mild or moderate dementia will be able to give some subjective description of how they are.

Contrary to conventional teaching, most people with mild dementia are very aware of change in mental skills. It is also extremely important to gather this description of change from at least one other person who knows them well. This can be an uncomfortable situation, but it is usually best to hold the interview together rather than to talk secretively. Quite commonly, an informant will be more concerned about mental skills than the patient. Sometimes a person will seek help alone, saying that they don’t want to worry their family, and in these cases dementia is less likely to be present.