Information

Sir Terry Pratchett and his rare Alzheimer's diagnosis

Posterior cortical atrophy diagnosis

In 2007, Sir Terry Pratchett publicly announced that he had a rare form of young-onset Alzheimer’s disease, called posterior cortical atrophy. 

The beloved author was well known for his humorous and thought-provoking fantasy novels. He announced his diagnosis with the condition at the age of only 59.

For many people, this will have been the first time they heard of posterior cortical atrophy (PCA for short). Here, we’ll discuss what is known about the condition.

Who gets PCA?

PCA often starts much earlier than more common types of dementia with diagnosis typically happening in a person’s mid-50s or early 60s.

We don’t have exact numbers but there are about 42,000 people in the UK with a form of dementia diagnosed before the age of 65. This is known as young-onset dementia. Only a small proportion of these are likely to have PCA though because it’s a rare type of dementia. 

Sir Terry Pratchett had a type of dementia that affects vision, not memory

Posterior cortical atrophy is usually caused by Alzheimer’s disease, which for most people causes problems with memory and thinking. However, with PCA the disease starts in an unusual place at the back of the brain, causing very different early symptoms.  

The back of the brain is where we make sense of what we see with our eyes. It enables us to clearly make out people or objects and then understand where they are in relation each other. Without it, we would just see visual noise, without meaning or usefulness. 

This is why PCA causes people to become more visually impaired over time, to the point where after several years or more with the condition they become functionally blind. 

An example of how vision is affected

The brain sees the contrast around the edge of the plate pictured below and concludes that it’s a separate object from the table underneath it. This allows a person to ‘see’ the plate. 

When the back of the brain gets damaged by disease, it gets harder to see shapes and work out what they are and where they are. It’s why the first signs of PCA are usually having difficulty seeing objects and judging distances, as well as finding it harder to read. 

Challenges that come with PCA vision loss 

A person with PCA may have problems reading because the shapes of the letters and words appear jumbled or don’t seem to mean anything.​

Some types of thinking are also affected that aren’t obviously visual in nature but still rely on this part of the brain. These include problems with spelling and arithmetic. This is because these skills rely on being able to create images in our mind.

Although PCA is rare, the visual problems it causes can also happen with more common types of dementia. 

Thanks to many wonderful volunteers with PCA who take part in research studies, we have learned a great deal about helping people with dementia who are having problems seeing things clearly. This includes using better contrast and bolder colours in living spaces and avoiding confusing patterns wherever possible. 

A progressive condition

As with other forms of dementia, there is no cure for posterior cortical atrophy.

As the disease progresses, most people will develop other symptoms that are more typical of Alzheimer’s disease, such as problems with memory and thinking. They may also experience unusual symptoms, such balance problems, dizziness, or consistently leaning to one side.

Treatments for Alzheimer’s disease may help to improve some of the symptoms of PCA, but their effects are modest and they do not slow down the progression of disease in the brain.

Just as with all types of dementia, people with PCA die earlier than they should do. The conditions causes them to become frail and lose weight and it makes other health problems so much more difficult to treat and care for. This makes it harder to recover fully from injuries and infections.

You can also call our Dementia Support Line on 0333 150 3456 to speak with our advisers, or discuss your experiences of dementia within our online support forum.