Before the best selling author Terry Pratchett announced he had been diagnosed with a rare form of Alheimer's, few people would ever have heard of Posterior Cortical Atrophy (PCA). First described by Frank Benson in 1988, and sometimes referred to as Benson's syndrome, PCA can be thought of as a visual variant of Alzheimer's due to the degeneration of the visual center of brain tissue at the back of the brain.
When Pratchett was told of his condition, he described the diagnosis as, "an embuggerance." With something approaching optimistic irony, Pratchett observed that if you're going to get Alzheimer's, it's at least the best form to have. With PCA, the person is left both fluent and coherent, yet memory and visual acuity is gradually lost.
For Terry Pratchett, the early signs involved an awareness that both his typing skills and his spelling were getting worse. At first, he was told that these were probably signs of an aging brain, but after an MRI scan and a battery of tests, the diagnosis was eventually confirmed.
The symptoms of PCA occur after the age of 50. Symptoms typically involved blurred vision, problems in following lines of text when reading and problems with depth perception. As the disease progresses, previously familiar places and faces are forgotten. The disease is not easy to diagnose and no specific test exists to identify its prescence. If the disease is suspected, a battery of psychological tests, neurological tests and brain imaging techniques are required before a diagnosis can be reached.
Comparatively little is known about PCA but like Alzheimer's disease, the brains of affected individuals show deposits of plaques and tangles. The disease progresses over several years and is characterised by visual agnosia (inability to recognize and identify objects or people) and apraxia (problems in executing movements despite having the physical ability to do so).
Typical daily tasks can present real problems. Dressing, for example, imitating movements, using keys, pens, or a razor are often ruled out. As the disease progresses, levels of visual agnosia progress to a point where the person is effectively blind. Eventually, language, reasoning and memory all become affected. There is no treatment for PCA. The course of the disease is between 8-12 years, from the onset of symptoms to death.
Terry Pratchett recognizes his celebrity status has given a much needed boost to public awareness of Alzheimer's disease. As he says, golden swords are best for slaying dragons, so his $1 million donation to Alzheimer's research will be welcomed.
In the absence of hard facts we are left with speculation as to the causes of certain diseases. Pratchett lays the blame on the old mercury amalgam fillings in his teeth, which he has now had removed. Although there is no scientific proof to support this view, Pratchett says some of his fans are pretty high up in the medical profession. He says he's been told that anything that reacts with mercury in your teeth is bound to have some effect. By his own admission he's trying things because he has the money. Pratchett is too young to be prescribed Aricept, so he's paying for his own.
Diagnosed in 2007, Pratchett gave an interview to the Times Online in May 2008. His condition was now affecting him in many more obvious ways. "I can spell 'transubstantiation' and in the next bit I can't spell 'colour' because it's as if bits of the network are switching on and off," he said.
"The future is going to happen whether I'm scared of it or not so I do my best not to be. Around about five o'clock in the morning things might be different but you just have to face it."
In a more optimistic moment Pratchett stated that researcher appeared to be on the right track and that in five years time the situation could be looking, "hopeful".