Dementia is a syndrome in which there is deterioration in memory, thinking, behaviour and the ability to perform everyday activities. Alzheimer’s disease is the most common type of dementia.
1. Cognitive impairment:
Cognitive decline is manifested as amnesia, aphasia, agnosia and apraxia (the 4As).
Characteristically, recent memories are lost before remote memories. With disease progression, even remote memories are lost.
Language problems are found in many patients at presentation, although the language deficits in AD are not as severe as those of the fronto-temporal degenerations.
Word-finding difficulties (nominal dysphasia) are the earliest phenomena observed. Although harder to
assess, receptive aphasia or comprehension of speech, is almost certainly affected. In the final stages of the disorder, speech is grossly deteriorated with decreased fluency, preservation, echolalia and abnormal non-speech utterances.
Patients with AD may have difficulty in recognizing as well as naming objects.
One particular agnosia encountered in AD is the loss of recognition of one’s own face (Autoprosopagnosia). This distressing symptom is the underlying cause of perhaps the only clinical sign in AD – “The Mirror Sign”.
Patients exhibiting this will interpret the face in the mirror as some other individual and respond by talking to it or by apparent fearfulness.
Loss of the ability to execute skilled tasks that are not due to motor impairment.
It is seen in moderate stages of AD. Typically, difficulties with dressing or tasks in the kitchen are noticed first ( but these are inevitably preceded by loss of ability for more difficult tasks).
2. Other cognitive impairment:
There appear to be no cognitive functions that are truly preserved in AD. Difficulties with calculation, attention, cognitive planning & visuospatial difficulties ( may result in wandering and becoming lost) also occur.
3. Functional impairment:
In Alzheimer’s disease functional abilities decline alongside cognitive abilities. The abilities to function in ordinary life (activities of daily living (ADLs)) are lost, starting with the most subtle and easily avoided and progressing to the most basic and essential.
The ability to use the telephone properly or to handle finances are lost early.
Self-care ADLs including dressing and personal hygiene and are also lost gradually.
Untidiness in clothing progresses to difficulties in dressing.
Personal hygiene becomes poor as dentures are not cleaned and baths taken less often, before finally assistance is required with all self-care tasks.
4. Neuropsychiatric symptoms:
The relationship between AD and depression is complex:
1. Depression is a risk factor for AD.
2. Depression can be confused with dementia (pseudodementia).
3. Depression occurs as part of dementia.
4. Cognitive impairments are found in depression.
A major depressive episode is found in approximately 10 per cent of patients & minor depressive episode in 25 percent.
Elation, disinhibition and hypomania all occur in AD but are relatively infrequent, elevated mood being found in only 3.5 per cent of patients.
The underlying cause of mood change in AD is not known. However, loss of serotonergic and noradrenergic markers accompanies cholinergic loss.
A majority of AD patients are reported to suffer from some form of psychotic symptom with delusions being more common than hallucinations.
Delusions are frequently paranoid and the most common delusion is one of theft.
Visual hallucinations are reported more commonly than auditory and other modalities are rare.
Psychosis can occur at any stage of the disease, although most studies find the maximal rate of psychosis in those with at least moderate dementia.
Family members describe the loss of personality as ‘living bereavement’ – the body remains, but the person once known has gone.
Personality changes include loss of awareness and abnormal response to the environment. Individuals may become more anxious or fearful. There is a flattening of affect and a withdrawal from challenging situations.
Catastrophic reactions occur when the patient is confronted and he/she cannot avoid such challenging situation.
Less commonly, personality changes may be of disinhibition with inappropriate sexual behaviours or inappropriate affect.
Aggressiveness is often accompanied by psychosis, but it may be part of a more general personality change.
(d) Other behavioural manifestations:
Behaviours exhibited in AD include wandering, changes in eating habit, altered sleep or circadian rhythms and incontinence.
Wandering may be a manifestation of topographical confusion, a need for the toilet or it may reflect hunger, boredom or anxiety.
Sleep is frequently disturbed, with many patients exhibiting altered sleep–wake cycles and others experiencing increased confusion towards evening.
- New Oxford Textbook of Psychiatry(2nd edition).