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Terry Pratchett and his rare Alzheimer's diagnosis

Following the BBC2 docu-drama about Terry Pratchett, read more about posterior cortical atrophy (PCA), the rare form of Alzheimer's disease he had.

In 2007, aged 59, Sir Terry Pratchett publicly announced that he had a rare form of early onset Alzheimer’s, called posterior cortical atrophy.

A docudrama on BBC2 followed the literary career of the beloved author, who was well known for his humorous and thought provoking fantasy novels. 

Here, Alzheimer’s Society Research Communications Officer Tim Shakespeare discusses what we know about posterior cortical atrophy.

Terry Pratchett and dementia

Before I joined Alzheimer’s Society, I carried out research into posterior cortical atrophy - the rare form of Alzheimer’s that Terry Pratchett was diagnosed with.

In this post I describe what it is, how it affects people, and what research is taking place. Just to warn you, the post discusses the end stages of Alzheimer’s disease which some may find upsetting.

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


For many people, the first time they heard of posterior cortical atrophy (PCA for short) will have been when Terry Pratchett announced his diagnosis with the condition

Posterior cortical atrophy literally means ‚Äėback of the brain shrinkage‚Äô. The back of the brain is where we interpret visual signals from the eyes and posterior cortical atrophy affects the ability of the brain to process these signals.

Symptoms of PCA can include difficulty reading, recognising objects and judging distances. Problems with spelling and calculation are common, as these skills rely on similar areas at the back of the brain.

Memory and language skills are usually less affected in the early stages of the condition, but as the disease spreads to more parts of the brain, people may develop more typical symptoms of Alzheimer’s disease such as memory loss and confusion.

Vision and perception can be affected by other types of dementia too, but in posterior cortical atrophy these are the first and most severe symptoms.

People tend to develop posterior cortical atrophy at a relatively young age, in their 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 that started before the age of 65, and of this group only a small proportion are likely to have posterior cortical atrophy.

Raising questions

From a scientific point of view, there’s an interesting question that could be answered with research into posterior cortical atrophy. People with posterior cortical atrophy have the hallmarks of Alzheimer’s disease in their brain (clumps of toxic proteins called amyloid and tau) but these clumps are found in back of the brain. In Alzheimer’s disease these toxic proteins are found in the memory centres, which is why memory loss is one of the main symptoms associated with this condition.


The reasons behind why Alzheimer’s disease can affect different parts of the brain in different people are not understood. There must be some genetic, lifestyle and/or environmental factors that cause the visual areas to be vulnerable or the memory centres to be protected in some people. Finding out what these are could give us important insights into Alzheimer’s disease.

It’s also important to improve our understanding of the symptoms that people with posterior cortical atrophy experience so that we can support them better.

Some of these symptoms might seem quite unusual, for example some individuals have a disordered sense of balance and they might experience dizziness or lean to one side. Alzheimer’s Society has given research funding to Professor Sebastian Crutch at UCL to investigate these balance problems. We hope the project will improve understanding, detection and management of these more unusual symptoms.

A progressive condition

As with other forms of dementia, there is no cure for posterior cortical atrophy, and how quickly the symptoms progress depends on the individual person.

Treatments that work for Alzheimer‚Äôs disease may help relieve symptoms for some people with posterior cortical atrophy, but over time the disease progresses to affect more aspects of thinking and more aspects of everyday life. Terry Pratchett grappled with the issues around the later stages of Alzheimer‚Äôs and discussed them in the years following his diagnosis.

The period when someone with dementia is approaching the end of their life is difficult and emotional. People with dementia have the right to dignity and a ‚Äėgood death‚Äô and people may wish to discuss these issues in different ways and at different stages. For those who wish to find out more, there is information about end of life care on our website.

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My sister has PCA and is now in the latter stages of the disease. The development of her disease was completely different from Alzheimer's. This caused her and us much distress in trying to help her deal with her disease. When she needed full time care, we were unable to find a care home which understood her condition and she and we were frustrated by the lack of awareness. She is now in a dedicated working age dementia home. I only wish we could have found it earlier. I am so glad that there is now funded research into this condition. If we can help in any way, please contact me.

On line there is a report by a Dr Mary Newport of Tampa , Florida. To the effect that Altzimers is a kind of diabetes of the brain whereby the brain cannot absorb glucose, but that taking pure Coconut oil enables the brain to digest the glucose via a substance called tryglissarines (may have misspelt that) and that there is a Professor Ceiran Clark at Oxford
University working along the same lines, has anyone heard of this and is there any sort of trial going on,

Hi Peter, thanks for your comment. We have a page on our website about coconut oil here which will give you some more information about this:…

My wife has been struggling with PCA for some years, although she was only diagnosed in 2015 at the age of 60, following a MRI scan showed her Right Parietal Lobe had all but gone. Prior to that her diagnoses was Mild Cognitive Impairment but as she said "there was nothing 'mild' about it for her"! Valdeana had dealt with visual and memory issues since the turn of the millennium, being diagnosed with a Holmes Adie Pupil in 2000, and if I read through the literature I can see minor incidents as far back as the mid 90's. Although we have been plagued by it's consequences for our careers, finances and health, I do feel that it's slow progression has allowed her brain to adapt, considering the total loss of the Right Parietal Lobe and 70% of her left Hippocampus I remain astonished by how she manages with the disabilities Alzheimer's inflicts. Today Valdeana is at daycare, to allow me to work part-time and time to deal with those things I can't deal with when being her carer. Many people who have family at the same Daycare do not, initially realise Valdeana is a suffer. What I would say is that Valdeana is still herself, just with a lot to deal with in her disabilities. She remains my fiery little Red-Head with a mind of her own. And for that, I'll always love her.

that is so sad and so tender. Thanks for sharing your thoughts. Your redhead sounds like a real cracker!

With PCA Valdeana is disabled but we still have Valdeana with us.

My mom, 76, was diagnosed with PCA. Can someone please give me an idea of what to expect? Will she forget who I am, will she need full time care, will she die???

Julie: I am so sorry about your mother. This is a very challenging diagnosis. My husband died one year ago at age 64 of PCA. I live in the US. I kept notes over the course of his progression (18 months) that you might find helpful in adjusting. It was entirely trial and error (many minor adjustments were a big help), but perhaps my solutions might help you with your mother. I was able to manage very him well at home until his death.

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