Vascular dementia is the second most common cause of dementia, accounting for about 20 per cent of all cases by itself and up to another 20 per cent in combination with Alzheimer’s disease. Alzheimer’s disease alone accounts for about 50 per cent.
It usually affects people between the ages of 60 and 75 and is slightly more common in men than women. Vascular dementia is a term for dementia associated with problems in the circulation of blood to the brain (cerebrovascular disease). It encompasses a wide range of diseases or disorders, the principal feature of which is loss of intellectual abilities. Unlike with most forms of Alzheimer’s disease, the cause of vascular dementia is known.
If blood vessels in the brain burst (cerebral haemorrhage), if arteries blocked by plaque formation or clots (thrombosis or embolism), or if there is insufficient blood flow to parts of the brain (ischaemia) brain tissue will die. This is often called a stroke.
It is thought that about a fifth of people who have strokes will develop problems involving their mental abilities including dementia. The risk factors for vascular dementia are those associated with all forms of stroke, the most significant of which is high blood pressure (hypertension).
Brain tissue may also die due to disease in the blood vessels. Following is an overview of types of vascular dementia, causes, diagnosis and progression. However, it is important to note that unlike with most Alzheimer’s cases, vascular dementia can be very difficult to distinguish from other forms of dementia and many researchers still do not agree on the various “types” of vascular dementia.
Research over the next five to ten years may significantly alter our understanding of vascular dementia. Causes of Vascular Dementia Vascular dementia can be caused in several different ways. Most commonly there is blockage of small blood vessels (arteries) deep within the brain. When any part of the body is deprived of blood, which carries oxygen and nutrients, it dies - this is called an infarct. When brain tissue dies it is also called a stroke. Blockages may be caused by build up of plaque on the inside of the arterial wall or by clots which have broken off, jamming a smaller tributary upstream. Clots can also result from abnormal heart rhythms, or other heart pathology, or can form on the inside of the major cartoid arteries that run up the side of the neck and supply the brain.
Rarer causes of vascular dementia are associated with auto-immune inflammatory diseases of the arteries such as Systemic Lupus Erythermotsis (SLE or Lupus) and Temporal Arteritis. Both of these can be treated with cortisone type drugs or other drugs to suppress the immune system. Finally, blood vessels may burst or haemorrhage. This is a dramatic event, often preceded or accompanied by severe headache, and leading to hospital admission. Defects are often severe. The patient’s history allows ready diagnosis of this type of vascular dementia. Some Risk Factors for Stroke
Among the different types of vascular dementia that have been identified, multi-infarct dementia (MID) is probably the most common. MID is caused by a number of small strokes, called ministrokes. These strokes may be silent in that no one may be aware they have occurred, but they can be seen on various brain scans. Sometimes the brain is damaged but not dead as a result of inadequate blood flow. This is called ischemia. If ischemia is severe, it causes an infarct. Some people also incorrectly use MID as a term for all types of vascular dementia. The strokes cause damage to the cortex of the brain - the area associated with learning, memory and language.
A person with MID is likely to have better insight into their condition in the early stages than people with Alzheimer’s disease and parts of their personality may remain relatively intact for longer. Transient ischemic attacks (TIAs) may be the precursors of vascular dementia. The symptoms of a TIA often are very slight. They may include mild weakness in an arm or leg, slurred speech and dizziness. The symptoms generally do not last for more than a few days, that is why they are called transient.
Often people with MID have trouble remembering things (especially recent events), find it difficult to communicate or follow a conversation, or appear generally confused. In addition, a person with MID may experience symptoms such as hallucinations (seeing or hearing things that are not real), delusions (firmly held false beliefs), or depression which may be treated with medication. People with MID can also experience emotional swings with laughter and tears occurring for no apparent reason, epileptic fits or partial or total paralysis of a limb. Because a stroke can occur anywhere in the brain, the symptoms that result can be quite varied.
Binswanger’s disease is a subcortical vascular dementia which was once considered rare but is now being reassessed, and may be relatively common. As with other vascular dementias, it is associated with stroke-related changes. It is the ‘white matter’ deep within the brain that is affected. It is caused by high blood pressure, thickening of the arteries and inadequate blood flow.
Symptoms often include slowness and lethargy, difficulty walking, emotional ups and downs and lack of bladder control early in the course of the disease, with gradually progressive dementia developing later. Most people with Binswanger’s disease have or have had high blood pressure.
Diagnosis of Vascular Dementia
People who show signs of dementia or who have a history of strokes should have a complete physical exam. The doctor will ask the patient and family about the person’s diet, medications, sleep patterns, personal habits, any history of high blood pressure, diabetes, abnormal heart rhythms and past strokes, other medical problems and recent stressful events in the person’s life that might account for the symptoms.
The doctor will look for signs of a stroke by checking for weakness or numbness in the arms or legs and difficulty with speech. Laboratory tests which may be done include a blood pressure reading, an electroencephalogram (EEG), and blood tests.
Brain imaging tests which the doctor may order include a computerised tomography (CT) scan or a magnetic resonance imaging (MRI) test. Both these tests take pictures of sections of the brain which are then displayed on a computer screen to allow the doctor to see inside the brain. They are painless and do not require surgery.
Additionally, the doctor may send the patient to a psychologist to test reasoning, learning ability, memory and attention span.
Using all these techniques, a probable diagnosis of vascular dementia can usually be made. However, as is the case with Alzheimer’s, a diagnosis of definite vascular dementia can only be made by examining the brain, usually at autopsy. Sometimes vascular dementia is difficult to distinguish from Alzheimer’s disease. It is possible for a person to have both vascular dementia and Alzheimer’s disease, making it hard to diagnose either.
Progression of Vascular Dementia
MID usually progresses gradually in a step-wise fashion in which the person’s abilities will deteriorate after a stroke and then stabilise until the next stroke. If further strokes do not occur, the abilities of people with vascular dementia may not continue to decline or, in some cases may improve. However, these improvements may not last. Sometimes the steps are so small that the decline appears gradual.
On average, people with vascular dementia decline more rapidly than people with Alzheimer’s disease, often dying from a heart attack or major stroke. Other vascular dementias, especially the ischaemic types, may decline in a smooth, gradual manner.
Prevention and treatment of Vascular Dementia
Because vascular dementia is caused by strokes, the risk factors for vascular dementia are the same as those associated with stroke-- high blood pressure, diabetes, high cholesterol and heart disease. To a large extent, these risk factors are controllable, unlike the only solidly established risk factors for Alzheimer’s disease, age, family history and Down syndrome and Apolipoprotein E status.
While no treatment can reverse damage that has already been done, treatment to prevent additional strokes is very important. To prevent additional strokes, medicines to control high blood pressure, high cholesterol, heart disease and diabetes can be prescribed. A healthy diet, exercise and avoidance of smoking and excessive alcohol also lessen the risk of further strokes.
Sometimes aspirin or other drugs are prescribed to prevent clots from forming in the small blood vessels. Drugs can also be prescribed to relieve restlessness or depression or to help the person with vascular dementia sleep better. In some cases, surgery known as carotid endarterectomy may be recommended to remove blockage in the carotid artery, the main blood vessel to the brain.
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