Symptoms of PCA explained

The common symptoms of posterior cortical atrophy, are to do with complex visual tasks. So people might notice difficulty reading, for example, finding their place when they’re reading, and when they’re moving from one line to another. They might find that words jump around the page, a bit like dyslexia. Other common symptoms that people describe, difficulty driving. So for example judging distances, the spacial perception of where they are relative to other things that can lead to small scrapes, or hitting the curb. That sort of thing, when people are driving. Other aspects controlled by the back of the brain can also be affected, like people’s spelling and their calculation, quite early on in the condition.

I’d like to think I know it as much about PCA as most people, but I wouldn’t be so bold as to say I know what the experience is like. I know what people have told me about it. I know, for example, people with PCA and their carers often describe their experience that visual world as being like looking through a cracked mirror, in the sense that everything is very fragmented. Things don’t cohere neatly together. They often perceive parts of the whole, but not the whole picture. And because it’s fragmented in that way, everything is very effortful for them.

Even identifying a face, even of a relative might be an arduous task where they’re piecing together different bits, and trying to put it together, and sort of weighing up the idea of different possibilities as to who it might be. Whereas for you and I our vision is so effortless. We have no idea quite how many complex calculations our brain is constantly performing every time we open our eyes, and take in the information about the world around us. And I think it’s also very stressful for people so tasks like crossing the road, are very scary for people with PCA.

If you can’t trust your vision, you look one way, you think you’ve tried to look for everything that might be relevant to you– cars coming towards you, cyclists, pedestrians. But actually you step out and suddenly there’s something there which you hadn’t seen at all. I think it must be extremely scary, and people lose a lot of confidence, I think, in their ability to move around. Sometimes people experience, what we call positive behaviours, so things that they see which shouldn’t be there, so washes of colour. And some people have reported odd experiences, like perceiving the reverse colours. I remember one lady, she was spreading out red bed sheets at home, and then looked at her hands and they were green.

So she had these sort of positive colour after images. So that’s one example of an odd symptom. Some people have difficulty perceiving large text as compared to small text. So several patients, have for example, noticed a difficulty reading, assumed it was something to do with their eyes, gone off to the library to get so-called easy to read books, and actually found those harder. I think the most striking example was a patient in one of Nick Fox’s clinics who had noticed on his way to work that he wasn’t able to read the headlines of his own newspaper. But then looked further down the carriage and saw someone else with the same newspaper, and was able to read their headlines.

Because by being further away the visual angle was reduced, and so it appeared to the brain, to the visual cortex to be smaller. And so those sorts of things are the kind of symptoms– and also even simple things like missing something that’s right in front of you, are all things which can be misperceived, or misinterpreted, as people just not paying attention, or perhaps being lazy, or careless in some way. And certainly driving instances, clipping wing mirrors which people attribute to being a bad driver, rather than because there’s something going on with your visual brain.