Vascular dementia

Information provided by the Alzheimers Society

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Vascular dementia is the second most common type of dementia (after Alzheimer's disease), affecting around 150,000 people in the UK. The word dementia describes a set of symptoms that can include memory loss and difficulties with thinking, problem-solving or language. In vascular dementia, these symptoms occur when the brain is damaged because of problems with the supply of blood to the brain. This factsheet outlines the causes, types and symptoms of vascular dementia. It looks at how it is diagnosed and the factors that can put someone at risk of developing it. It also describes the treatment and support that are available.

Causes

Vascular dementia is caused by reduced blood supply to the brain due to diseased blood vessels.

To be healthy and function properly, brain cells need a constant supply of blood to bring oxygen and nutrients. Blood is delivered to the brain through a network of vessels called the vascular system. If the vascular system within the brain becomes damaged - so that the blood vessels leak or become blocked - then blood cannot reach the brain cells and they will eventually die.

This death of brain cells can cause problems with memory, thinking or reasoning. Together these three elements are known as cognition. When these cognitive problems are bad enough to have a significant impact on daily life, this is known as vascular dementia.

Types of vascular dementia

There are several different types of vascular dementia. They differ in the cause of the damage and the part of the brain that is affected. The different types of vascular dementia have some symptoms in common and some symptoms that differ. Their symptoms tend to progress in different ways.

Stroke-related dementia

A stroke happens when the blood supply to a part of the brain is suddenly cut off. In most strokes, a blood vessel in the brain becomes narrowed and is blocked by a clot. The clot may have formed in the brain, or it may have formed in the heart (if someone has heart disease) and been carried to the brain. Strokes vary in how severe they are, depending on where the blocked vessel is and whether the interruption to the blood supply is permanent or temporary.

Post-stroke dementia

A major stroke occurs when the blood flow in a large vessel in the brain is suddenly and permanently cut off. Most often this happens when the vessel is blocked by a clot. Much less often it is because the vessel bursts and bleeds into the brain. This sudden interruption in the blood supply starves the brain of oxygen and leads to the death of a large volume of brain tissue.

Not everyone who has a stroke will develop vascular dementia, but about 20 per cent of people who have a stroke do develop this post-stroke dementia within the following six months. A person who has a stroke is then at increased risk of having further strokes. If this happens, the risk of developing dementia is higher.

Single-infarct and multi-infarct dementia

These types of vascular dementia are caused by one or more smaller strokes. These happen when a large or medium-sized blood vessel is blocked by a clot. The stroke may be so small that the person doesn't notice any symptoms. Alternatively, the symptoms may only be temporary - lasting perhaps a few minutes - because the blockage clears itself. (If symptoms last for less than 24 hours this is known as a 'mini-stroke' or transient ischaemic attack (TIA). A TIA may mistakenly be dismissed as a 'funny turn'.)

If the blood supply is interrupted for more than a few minutes, the stroke will lead to the death of a small area of tissue in the brain. This area is known as an infarct. Sometimes just one infarct forms in an important part of the brain and this causes dementia (known as single-infarct dementia). Much more often, a series of small strokes over a period of weeks or months lead to a number of infarcts spread around the brain. Dementia in this case (known as multi-infarct dementia) is caused by the total damage from all the infarcts together.

Subcortical dementia

Subcortical vascular dementia is caused by diseases of the very small blood vessels that lie deep in the brain. These small vessels develop thick walls and become stiff and twisted, meaning that blood flow through them is reduced.

Small vessel disease often damages the bundles of nerve fibres that carry signals around the brain, known as white matter. It can also cause small infarcts near the base of the brain.

Small vessel disease develops much deeper in the brain than the damage caused by many strokes. This means many of the symptoms of subcortical vascular dementia are different from those of stroke-related dementia.

Subcortical dementia is thought to be the most common type of vascular dementia.

Mixed dementia (vascular dementia and Alzheimer's disease)

At least 10 per cent of people with dementia are diagnosed with mixed dementia. This generally means that both Alzheimer's disease and vascular disease are thought to have caused the dementia. The symptoms of mixed dementia may be similar to those of either Alzheimer's disease or vascular dementia, or they may be a combination of the two.

Symptoms

How vascular dementia affects people varies depending on the different underlying causes and more generally from person to person. Symptoms may develop suddenly, for example after a stroke, or more gradually, such as with small vessel disease.

Some symptoms may be similar to those of other types of dementia. Memory loss is common in the early stages of Alzheimer's, but is not usually the main early symptom of vascular dementia.

The most common cognitive symptoms in the early stages of vascular dementia are:

problems with planning or organising, making decisions or solving problems

•difficulties following a series of steps (eg cooking a meal)

•slower speed of thought

•problems concentrating, including short periods of sudden confusion.

A person in the early stages of vascular dementia may also have difficulties with:

memory - problems recalling recent events (often mild)

•language - eg speech may become less fluent

•visuospatial skills - problems perceiving objects in three dimensions.

As well as these cognitive symptoms, it is common for someone with early vascular dementia to experience mood changes, such as apathy, depression or anxiety. Depression is common, partly because people with vascular dementia may be aware of the difficulties the condition is causing. A person with vascular dementia may also become generally more emotional. They may be prone to rapid mood swings and being unusually tearful or happy.

Other symptoms that someone with vascular dementia may experience vary between the different types. Post-stroke dementia will often be accompanied by the obvious physical symptoms of the stroke. Depending on which part of the brain is affected, someone might have paralysis or weakness of a limb. Or if a different part of the brain is damaged they may have problems with vision or speech. With rehabilitation, symptoms may get a little better or stabilise for a time, especially in the first six months after the stroke.

Symptoms of subcortical vascular dementia vary less. Early loss of bladder control is common. The person may also have mild weakness on one side of their body, or become less steady walking and more prone to falls. Other symptoms of subcortical vascular dementia may include clumsiness, lack of facial expression and problems pronouncing words.

Progression and later stages

Vascular dementia will generally get worse, although the speed and pattern of this decline vary. Stroke-related dementia often progresses in a 'stepped' way, with long periods when symptoms are stable and periods when symptoms rapidly get worse. This is because each additional stroke causes further damage to the brain. Subcortical vascular dementia may occasionally follow this stepped progression, but more often symptoms get worse gradually, as the area of affected white matter slowly expands.

Over time a person with vascular dementia is likely to develop more severe confusion or disorientation, and further problems with reasoning and communication. Memory loss, for example for recent events or names, will also become worse. The person is likely to need more support with day-to-day activities such as cooking or cleaning.

As vascular dementia progresses, many people also develop behaviours that seem unusual or out of character. The most common include irritability, agitation, aggressive behaviour and a disturbed sleep pattern. Someone may also act in socially inappropriate ways.

Occasionally a person with vascular dementia will strongly believe things that are not true (delusions) or - less often - see things that are not really there (hallucinations). These behaviours can be distressing and a challenge for all involved.

In the later stages of vascular dementia someone may become much less aware of what is happening around them. They may have difficulties walking or eating without help, and become increasingly frail. Eventually, the person will need help with all their daily activities.

How long someone will live with vascular dementia varies greatly from person to person. On average it will be about five years after the symptoms started. The person is most likely to die from a stroke or heart attack.

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