Types of vascular dementia
There are several different types of vascular dementia. The most common is subcortical vascular dementia, and other types can be caused by a stroke or smaller kinds of stroke.
This section covers four different types of vascular dementia. We look at the causes, symptoms, and how they progress:
Subcortical vascular dementia
Subcortical vascular dementia is thought to be the most common type of vascular dementia.
It is caused by diseases of the very small blood vessels that lie deep in the brain (known as ‘small vessel disease’). Over time, these blood vessels can develop thick walls and become stiff and twisted, so blood cannot travel through them easily. The parts of the brain supplied by these blood vessels become starved of oxygen and nutrients. Eventually they stop working altogether and the affected brain cells are lost.
Vascular dementia caused by small vessel disease happens slowly and gradually over time. Most of the damage happens in a part of the brain called the ‘subcortex’. This is very important for connecting all the different parts of the brain together so that information can be processed quickly. It is also important for expressing and controlling emotions. A person with subcortical vascular dementia may find these abilities are particularly affected
The symptoms of subcortical vascular dementia tend to be more consistent than other types of vascular dementia. Early loss of bladder control is common, which causes incontinence.
A person may also have difficulties with movement, such as being weaker on one side of their body, or becoming less steady and more likely to fall when walking. Other symptoms may include clumsiness, lack of facial expression and problems pronouncing words.
Vascular dementia can also be caused by a stroke. This is when the blood supply to a part of the brain is suddenly cut off.
With 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, if someone has heart disease, it may have formed in the heart and been carried to the brain. Sometimes, it is because the vessel bursts and bleeds into the brain, but this is much less common.
Some strokes are more severe than others. It depends on where the blocked vessel is and how long the blood supply is interrupted (this can be permanent or temporary).
Many people who have problems with their thinking during the weeks and months after a stroke do not develop dementia. Some of these people may improve over time. However, about one in five people go on to develop vascular dementia within six months. For these people, their condition will get worse over time.
Someone who has already had a stroke is also at greater risk of having another one. This is because the health problems that led to their original stroke (such as high blood pressure or heart problems) can cause another clot to happen. The more strokes that someone has, the more of their brain function they will lose overall. This means that they are more likely to develop dementia.
The symptoms of post-stroke vascular dementia can depend on which part of the brain has been damaged. For example, damage to the parts of the brain that control language or how we deal with emotions causes problems in these areas. A stroke may also cause physical difficulties such as paralysis, weakness of a limb, speech problems or trouble swallowing.
With rehabilitation, symptoms may get a little better or stabilise for a time, especially in the first few weeks and months after the stroke.
Multi-infarct dementia is caused by a series of smaller strokes. This may also include transient ischaemic attacks (TIA). A TIA is similar to a stroke but the symptoms last only a short time and tend to get better by themselves.
Some people may not realise that they have had smaller strokes or a TIA. Even if these symptoms get better quickly, it is still worth contacting the person’s GP to tell them what has happened as it could mean that their treatment needs to be changed.
Sometimes a blocked blood vessel is cleared after a few minutes, either by itself or with medical treatment. This means that the symptoms of the stroke (such as weakness down one side of the body, or slurred speech) may only be temporary. They may get better quickly once the blood vessel is unblocked.
If the blood supply is interrupted for more than a few minutes or hours, the stroke may lead to permanent brain damage. The areas of the brain affected by these strokes are known as ‘infarcts’. If a person has several smaller strokes over time, multiple infarcts will build up in their brain. They may eventually develop dementia if the combined damage of all these infarcts is enough to cause problems with memory, thinking or reasoning.
At least one in every ten people with dementia is diagnosed with mixed dementia.
This is when their dementia is caused by more than one condition. Most often it is a combination of Alzheimer’s disease and vascular dementia.
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