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Dementia
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About 5% of the general population over 65 years suffer from severe cognitive impairment with a further 5% showing mild changes, which may progress with time. Dementia refers to a global impairment of mental function which follows a chronic and progressive course. The symptoms and signs have usually been present for at least 6 months. The impairment of mental function is commonly associated with a deterioration in emotional control, social behaviour, motivation and the ability to perform activities of daily living (ADLs). These "non-cognitive" features of dementia, which are often the most upsetting aspects for family carers and friends, tend now to be referred to as Behavioural and Psychological Symptoms in Dementia (BPSD). Dementia is related to progressive cerebral degeneration, which may be caused by a variety of pathological processes, such as Alzheimer's disease, vascular dementia and dementia with Lewy bodies. Post mortem changes found in the brains of people with dementia suggest the following diagnoses (approximate figures):
50% |
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15% |
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15% |
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Mixed vascular/Alzheimer's disease |
15% |
5% |
Alzheimer's disease
Alzheimer's disease is characterised by a gradual insidious onset and progressive course, often beginning with memory failure before other cognitive functions (e.g. language, praxis) become affected. Non-cognitive features (depression, psychosis, wandering, aggression, incontinence) are common. Physical examination is often normal, as are routine blood investigations.
Computerized tomography (CT) scans may be normal or show generalised atrophy and dilatation of ventricles. CT scans also play a role in excluding other possible causes of confusion (e.g. space-occupying lesions, haemorrhages). Angled CT scans afford better views of the medial temporal lobes, which can show marked atrophy. However, this is not specific for Alzheimer's disease. Hippocampal atrophy is also seen with magnetic resonance imaging (MRI) scanning. Single photon emission computerized tomography (SPECT) provides information on how the brain is functioning, usually by tracing blood flow using radio-labelled technetium. In Alzheimer's disease SPECT scanning can show a generalized decrease in blood flow, or biparietal and bitemporal hypoperfusion. However, the diagnosis must always be made on the basis of the overall clinical presentation rather than solely on the appearance of scans.
Dementia with Lewy bodies
Dementia with Lewy bodies is characterised by the triad of fluctuating cognitive impairment, recurrent visual hallucinations and spontaneous parkinsonism, though not all occur in every patient. As with Alzheimer's disease, onset is insidious and may begin with cognitive problems, parkinsonism, or both. Cognitive impairment initially affects attentional and visuospatial function, with memory initially relatively spared. As with Alzheimer's disease, non-cognitive features are common. Parkinsonism consists mainly of bradykinesia rather than tremor and, once again, routine blood investigations are normal. CT scan may be normal or show generalised atrophy and dilatation of ventricles, with less temporal lobe atrophy than in AD. Blood flow SPECT can show similar changes to those seen in Alzheimer's disease, though DLB is more likely to be associated with occipital hypoperfusion than Alzheimer's disease, a finding which may relate to the hallucinations and visuospatial disturbance. Parkinsonism in DLB is associated with nigrostriatal degeneration, similar to that seen in Parkinson's disease. It is possible to image nigrostriatal degeneration using SPECT scanning with a ligand for the dopamine transporter (FP-CIT or "DaTSCAN" imaging) which can be helpful in assisting with the diagnosis of Parkinson's disease. In the future it is hoped such imaging methods may be helpful in diagnosing DLB as well.
Vascular dementia
In contrast, vascular dementia usually has an abrupt onset, often in association with a recognised stroke, and is associated with a fluctuating course, a stepwise decline and often reasonable insight at least in the early stages of illness. An exception to this course is subcortical vascular dementia, which may cause some 20% of all vascular dementia, when sudden onset and a stepwise course may not be seen. Patients will often have risk factors for vascular disease, for example high or low blood pressure, ischaemic heart disease or peripheral vascular disease, but also diabetes mellitus and hypercholesterolaemia. Physical examination is likely to reveal focal neurology and a CT scan would be expected to show evidence of cerebrovascular disease.
Other dementias
Other causes include rarer degenerative processes, e.g. Fronto-temporal dementia, Huntington's disease, in addition to alcoholic dementia, tumours, haematoma, etc. In some cases no discernible pathology is found.
A useful source for information on all matters relating to dementia is the Alzheimer's Society website: www.alzheimers.org.uk
Clinical assessment and management
By careful history taking (usually from patient and informant) and examination of both physical (particularly neurological) and mental state, it is possible to predict the likely underlying pathology in most patients with dementia. No specific diagnostic tests are yet available, but clinical diagnosis may be usefully supported by structural brain imaging methods such as CT or MRI scanning and functional imaging techniques such as SPECT (Single Photon Emission Computer Tomography) scanning. It is important to develop methods of establishing the aetiology of dementia during lifetime:
- To assist in predicting course of illness and determining prognosis.
- To inform management decisions; for example specific treatments are becoming available for Alzheimer's disease (cholinesterase inhibitors) and vascular dementia and it is necessary to know which patients should receive which treatment.
Patients with dementia usually present either because of failure to cope or with disturbed behaviour occasionally with both. They often lack insight into their illness or, in the early stages, deny it. People with dementia require:
- An assessment of the cause and severity of the dementia (cognitive impairment and behavioural abnormalities);
- An assessment of deficits in function and the need for care (dependency);
- An assessment of the person's social situation;
- Provision of treatment and care appropriate to the identified needs;
- Support for carers - both practical and emotional;
- Review of the above points - is the treatment and care appropriate and beneficial?
About 50% of cases of dementia have concurrent physical health problems. The burden of care produced by a physically sick patient with dementia is greater than that of a fit one; therefore, diseases should be sought and treated where appropriate. Dementia may also be complicated by:
- Emotional lability
- Depression
- Psychotic features (i.e. delusions and hallucinations)
- Behavioural disturbances (i.e., wandering, aggression, incontinence)
These may be helped by pharmacotherapy, counselling and explanation and support to relatives. Such patients may respond either to antidepressants for lability and depression, or antipsychotic agents for psychotic features and some behavioural disturbances. Patients with dementia are often sensitive to side effects of psychotropic drugs and so it is important to begin therapy with very low doses of medication and monitor carefully for side-effects, particularly extrapyramidal problems. In 2004, the two drugs risperidone and olanzapine were recommended not to be used for the control of agitation and disturbed behaviour in dementia because of the risk of stroke. The use of antipsychotic medication to control agitation and other difficult behaviours in moderate to severe dementia remains common but controversial.
Memory Clinics
The assessment of forgetfulness is often undertaken by memory clinics. These exist in a variety of forms (some being very clinically focused and others having a research basis). The aim is to provide thorough assessment (clinical history, with mental state, neuropsychological and physical examinations and appropriate investigations e.g. blood tests and neuroimaging) in order to arrive at an accurate diagnosis. Some clinics then initiate and monitor the use of medication (e.g. the cholinesterase inhibitors for Alzheimer's disease). Increasingly, memory clinics are seeing people with milder symptoms, many of whom will be anxious about the possibility of dementia. Some such patients will have other conditions, such as depression (i.e."pseudodementia") or other physical illnesses.
The diagnosis of "mild cognitive impairment" (MCI) is now sometimes made in people who present with forgetfulness but who do not satisfy the criteria for even a mild dementia (because, for instance, their everyday activities are not impaired). A proportion of people given the diagnosis of MCI will progress to develop dementia on followed-up. Identifying MCI may, therefore, open up the possibility of early treatment. But MCI is not uncontroversial, because some people given this label will show no such progression of symptoms and might be more properly regarded as "normal".
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