Parkinson's disease dementia

What is Parkinson’s disease dementia?

Parkinson’s disease is a brain disease that affects around 145,000 people in the UK.

At first it mainly causes problems with movement. However, after a few years some people also start to have problems with thinking, memory and perception.

These symptoms are mild at first and for many people they do not get much worse. However, around a third of people with Parkinson’s eventually develop dementia. 

The disease that causes Parkinson’s is very similar to the one that causes dementia with Lewy bodies (DLB).

In fact, many scientists consider these two conditions to be the same disease but with different starting places in the brain.

In Parkinson’s dementia the movement symptoms are the first to show followed later by dementia, whereas for DLB it’s typically the other way around.

Symptoms of Parkinson’s dementia

Symptoms vary and can change quickly from hour to hour. However, most people have symptoms very similar to those of dementia with Lewy bodies. These include:

• problems with staying focused
• difficulties with making decisions
• memory loss and forgetfulness
• problems with the way the person sees things around them.

As well as problems with memory and thinking, Parkinson’s dementia also often causes:

• problems staying fully awake
• very disturbed sleep
• visual hallucinations - seeing things which are not really there
• delusions – thinking things that aren’t true
• changes in appetite
• mood symptoms, such as depression, anxiety, or apathy.

Treatments for Parkinson’s dementia

During the first few years of having Parkinson’s, problems with movement can normally be treated with medicines that replace a natural chemical in the brain called dopamine.

However, as the disease progresses, these medicines tend to become less effective. They can also make symptoms of dementia worse too – particularly hallucinations and delusions.

Doctors treating Parkinson’s try to balance the benefits that dopamine-boosting medicines can have on a person’s movement symptoms against the risk that they could cause a worsening of dementia symptoms.

Most often this means that they can only prescribe these medicines in smaller doses. Having dementia can therefore make living with Parkinson’s much more challenging.

It is very important that someone with Parkinson’s dementia should never be treated with medicines that are used to treat hallucinations and delusions in other people, known as antipsychotics.

For someone with Parkinson’s dementia, antipsychotics can cause a rapid worsening of their symptoms and can also be very dangerous. 

Some of the medicines used to help with memory and thinking in Alzheimer's disease can be helpful for someone with Parkinson’s dementia – particularly they are having hallucinations or delusions. 

Other types of treatments that don’t involve medicines, such as physiotherapy or speech therapy, may also help people to manage their symptoms.