Alzheimer's disease affects 400 000 people in the United Kingdom and as such is the commonest cause of dementia. Although predominantly a disease of old age, it is not confined to the elderly population; about 18 000 of those affected are below retirement age, and some have symptoms as early as their fourth decade.
The term Alzheimer's disease refers to the clinico-pathological entity of the histological changes of neurofibrillary tangles and senile plaques in a patient with dementia. A definite diagnosis therefore relies on confirmation at postmortem examination or by cerebral biopsy. Apart from histology there are, as yet, no specific tests for the disease; this means the diagnosis usually remains a clinical one. Furthermore, the key clinical feature of dementia can be due to many different causes; it is a clinical presentation of grave importance.
Clinical approach to the patient with possible Alzheimer's disease
The first point to establish is whether the patient is cognitively impaired. In most instances this impairment will be synonymous with dementia, although on first presentation the patient may have a relatively circumscribed cognitive impairment; this is typically a memory deficit. As the disease progresses, cognitive impairment becomes generalised--that is, the patient fulfils the criteria of dementia (box 1). Several criteria and definitions of dementia have been developed; all include the central feature of multiple domains of cognitive impairment (for example, dysphasia, memory impairment, visuospatial impairment) sufficient to interfere with social and work function. These definitions specifically exclude patients with disturbances of arousal. To assess the extent of cognitive impairment it is essential that a member of the family (commonly the spouse) or a friend is interviewed since patients with dementia may be unaware of their deficit (they may have an anosognosia). It is important to inquire about difficulties at work and any tendency to mislay items, forget appointments and names, fail to recognise people, or get lost when alone. Changes in family roles are useful clues--for example, a person who normally deals with the family finances may recently have given up because of failing memory. A number of brief cognitive assessment schedules (for example, the mini mental state examination and the abbreviated mental test score) are available, but these cannot be used to provide precise numerical cut offs for the diagnosis of dementia. They are, however, useful as rapid beside tests and usually take no more than 10 minutes to complete.
The next point to establish is whether the cognitive impairment might relate to depression or anxiety. Again, clues will be available in the history both from the patient and from the accompanying family member. In general, patients with cognitive impairment due to Alzheimer's disease underestimate the severity of …