Dementia Types

Dementia Types

There are many types of dementia caused by different brain diseases. Dementia is the umbrella term for a number of neurological conditions, of which the major symptom includes a global decline in brain function. We now know dementia is a disease symptom, and not a normal part of aging. There are over 100 diseases that may cause dementia. The most common causes of dementia are:

• Alzheimer’s disease
• Vascular dementia
• Lewy body disease
• Fronto-temporal dementia (including Pick’s disease)

The boundaries between the different types are not necessarily distinct. Alzheimer’s disease and vascular dementia are responsible for up to 90% of cases of dementia.

Vascular Dementia

Vascular dementia is the second most common cause of dementia after Alzheimer’s disease. It is the broad term for dementia associated with problems of circulation of blood to the brain. There are a number of different types of Vascular dementia. Two of the most common are Multi-infarct dementia and Binswanger’s disease.

Multi-infarct dementia

This is probably the most common form of Vascular dementia. Multi-infarct dementia is caused by a number of small strokes, called mini-strokes or Transient Ischaemic Attacks (TIA). The strokes cause damage to the cortex of the brain, the area associated with learning, memory and language. A person with Multiinfarct dementia is likely to have better insight in the early stages than people with Alzheimer’s disease, and parts of their personality may remain relatively intact for longer. Symptoms may include severe depression, mood swings and epilepsy.

Binswanger’s disease (also known as Subcortical vascular dementia)

This was thought to be rare, but is now being reassessed, and may in fact 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. Most people with Binswanger’s disease have, or have had, high blood pressure. One single large stroke can sometimes cause Vascular dementia depending on the size and location of the stroke. Risk factors that make strokes more likely to lead to Vascular dementia include:

• Untreated high blood pressure (hypertension)
• Atrial fibrillation
• Other irregular heart rhythms which raise the risk of clots and atherosclerosis (fatty deposits in blood vessels) which causes damage to the arteries of the brain.

Who gets vascular dementia?

Anyone can be affected by Vascular dementia, but several factors increase the risk. These include:

• High blood pressure
• Smoking
• Diabetes
• High cholesterol
• History of mild warning strokes
• Evidence of disease in arteries elsewhere
• Heart rhythm abnormalities

Vascular dementia is slightly more common in men than women.

Is there treatment available?

While no treatment can reverse damage that has already been done, treatment to prevent additional strokes is very important. To prevent 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 dementia to 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. Recent research suggests that cholinesterase inhibitor medications such as Donepezil (Aricept) and Galantamine (Reminyl), which are helpful for some people with Alzheimer’s disease, may also be of some benefit to some people with Vascular dementia. However, the evidence is not yet as clear or compelling as that for the use of these medications with Alzheimer’s disease. Support is available for the person with Vascular dementia, their families and carers. This support can make a positive difference to managing the condition. Alzheimer’s Australia provides support, information, education and counselling for people affected by dementia. Up-to-date information about drug treatments is also available from Alzheimer’s Australia.

Lewy body disease

Lewy body disease is a common form of dementia, sharing many similarities with Alzheimer’s disease. Lewy body disease is caused by the degeneration and death of nerve cells in the brain. The name comes from the presence of abnormal spherical structures, called Lewy bodies, which develop inside nerve cells. It is thought that these may contribute to the death of the brain cells. They are named after the doctor who first wrote about them. It is sometimes referred to as Diffuse Lewy body disease.

What is the cause?

At present there is no known cause of Lewy body disease, and no known risk factors have been identified. There is no evidence that it is an inherited disease.

How is lewy body disease diagnosed?

This type of dementia is diagnosed by taking a careful history of the pattern of symptoms, and by excluding other possible causes such as Vascular dementia and Alzheimer’s disease. A brain scan may reveal brain degeneration, but the Lewy bodies can only be identified by examination of brain tissue after death. Lewy body disease is similar to Alzheimer’s disease in many ways, and in the past it has sometimes been difficult to distinguish the two. It has only recently been accepted as a disease in its own right. It can occur by itself or together with Alzheimer’s disease and/or Vascular dementia. It may be hard to distinguish Lewy body disease from Parkinson’s disease, and some people with Parkinson’s disease develop a dementia which is similar to that seen in Lewy body disease.

What are the symptoms?

The symptoms of dementia with Lewy body disease include:

• Difficulty with concentration and attention
• Extreme confusion
• Difficulties judging distances, often resulting in falls.

There are also three cardinal symptoms, two of which must be present in order to make the diagnosis:

• Visual hallucinations
• Parkinsonism (tremors and stiffness similar to that seen in Parkinson’s disease)
• Fluctuation in mental state so that the person may be lucid and clear at one time and confused, disoriented and bewildered at other times. Typically this fluctuation occurs over a period of hours or even minutes and is not due to any underlying acute physical illness.

Some people who have Lewy body disease may also experience delusions and/or depression.

Temporal Lobes:

The right and left temporal lobes are involved in the organisation of sensory input such as what you hear or see. Damage may lead to difficulty placing words or pictures into categories. There is considerable difference in FTLD symptoms depending on which parts of the frontal and temporal lobes are affected. The three main subtypes or variants are:

• Fronto Temporal Dementia (FTD) is the most common subtype or Frontal Variant. It is mainly a disorder of behaviour. People with FTD may be disinhibited or apathetic
• Progressive non-Fluent Aphasia (PA), which was formerly known as Primary Progressive Aphasia (PPA). People with PA may lose the ability to speak or may begin to speak gibberish
• Semantic Dementia (SD) (Progressive Fluent Aphasia) is also known as the Temporal Variant. People with SD may lose the meaning of words and also may become preoccupied with a single activity Although people with FTLD may be assessed as one of the three subtypes above, the disease will progress and people with FTLD are likely to develop signs and symptoms that are a mixture of two or three subtypes.

FTLD causes progressive and irreversible decline in a person’s abilities over a number of years.