Quels sont les différents types de démence ?

SelonAlzheimer's Society, there are around 520,000 people in the UK with dementia - a set of symptoms that may include memory loss and difficulties with thinking, problem-solving or language.

The majority - 66% - have Alzheimer's. While 20% have vascular dementia, 15% have Lewy body dementia, and under five% have a condition called frontotemporal dementia.

In addition, there are some rarer forms of the disease including types related to alcohol and HIV, where the brain can be affected.

What's the difference?

All types of dementia are caused by some sort of damage to brain cells, which may result in memory loss, confusion, and difficulty with language and communication. The specific symptoms that someone with dementia experiences will depend on the parts of the brain that are damaged and the specific condition that is causing it.

Maladie d'Alzheimer

Alzheimer can be identified by the build-up of certain proteins in the brain which form plaques or 'tangles'. These disturb the communication between the nerves, which results in the cells dying and the loss of brain tissue.

At the same time, people with Alzheimer's are short of some chemicals in the brain which help transmit messages. The disease is progressive so symptoms worsen over time.

Démence vasculaire

Vascular dementia occurs when the blood supply to the brain is reduced. In many cases, the patient suffers multiple small les AVC, each of which may affect such a small part of the brain that it doesn't cause recognisable symptoms on its own.

A single major stroke can have the same effect. Without oxygen and nutrients from the blood, brain cells can't function properly and will die. When this happens, problems with cognition can occur.

Lewy body dementia

Lewy body dementia (LBD) is caused by tiny deposits of protein laid down in the brain. 'Lewy bodies' are named after the German doctor who first identified them. No one knows exactly what causes these proteins but they are linked to low levels of important chemicals in the brain which carry messages between nerve cells.

Lewy bodies are also involved in the development of la maladie de Parkinson. A brain scan can show the tiny deposits but it may take more detailed scans to interpret these correctly. Lewy bodies at the base of the brain are closely linked to movement, whereas deposits on the outer edges of the brain affect cognitive function (memory and perception).

LBD usually affects people over the age of 65. Although only 4% of people with dementia are diagnosed with LBD, it's estimated that it's often incorrectly diagnosed as Alzheimer's or vascular dementia and that 10-15% of people may actually suffer from it.

LBD has some of the symptoms of Alzheimer's and of Parkinson's. But other signs are unique. These can include a wide variation in mental ability over a day or even hours, problems with movement (a shuffling walk for instance), and hallucinations or delusions. This means that someone with LBD can have changes in their mental ability and with movement at the same time.

People with Parkinson's are at increased risk of developing dementia (Parkinson's disease dementia) as their condition progresses, especially if they have developed Parkinson's late on in life or have had it for many years.

Démence frontotemporale

Frontotemporal dementia (FTD) tends to affect younger people aged 45-65. It occurs when brain cells at the front or the temporal region of the brain die. The symptoms are changes in personality, behaviour and communication. This type of dementia can affect people younger than 45, or older than 65, but compared to people with Alzheimer's, it is the most common type of dementia in younger people.

How is dementia diagnosed?

Hannah Churchill, research communications officer fromAlzheimer's Society explains: "There is no single test for dementia. Most people will undergo a series of investigations, often initially with their GP where their general health will be taken into account too."

Initially, this may include a discussion about symptoms, such as memory loss or confusion, and the GP can do blood tests and a simple memory test. The next stage can be a referral to a memory clinic where further memory tests can be done.

If this is not conclusive, what next? Churchill advises: "A brain scan, such as an IRM ou CT scan can be done."

These investigations can show a history of small strokes, the presence of Lewy bodies, the tangles of proteins associated with Alzheimer's, or vascular deterioration in the small blood vessels. The diagnosis is made by a neurologist or a similar specialist.

Prochaines étapes

Churchill says: "There is no cure currently for any type of dementia and most are progressive but at different rates. When symptoms are mild or moderate, no treatment tends to be offered, other than suggestions on lifestyle which may slow down the progress." A group of drugs called the acetylcholinesterase inhibitors, which work by increasing levels of the chemical acetylcholine in the brain, are licensed for the treatment of Alzheimer's (including mild or moderate disease). They may improve certains of the symptoms affecting thinking and memory in about half of people with Alzheimer's disease.

Drugs can tackle the symptoms when they are more severe, such as agitation, hallucinations or low mood, but they don't halt the progression of the disease. However, Churchill reveals that a drug called trazodone, which is currently used for depression, has shown promise in recent research for treating the disease. But far more studies are needed first, as such results have only been seen in mice so far.

Lifestyle changes may slow down the progress of dementia as well as preventing it. Alzheimer's Society suggests that stopping smoking, taking regular exercise, eating a healthy diet and reducing your alcohol intake are definitely worth trying. Keeping your mind stimulated by reading, writing or learning a new skill could also potentially lower your risks of developing dementia in the future.