A large international study has revealed how posterior cortical atrophy, which includes various visuospatial symptoms, can manifest itself four years before the first memory deficits.
For some patients suffering from Alzheimer’s the early signs of the disease are not memory loss, but rather poor eyesight due to a little-known variant of the pathology: theposterior cortical atrophy (PCA) . These very unusual symptoms can make difficult to diagnose correct, which for thousands of people could arrive years late. Until now, little was known about posterior cortical atrophy, but a large, first-of-its-kind international study led by researchers at the University of California, San Francisco and published in Lancet Neurology has thoroughly investigated this different form of Alzheimer’s. Also participating in the work were the University of Trento, the Vita e Salute University of San Raffaele in Milan with Professor of Neurology Federica Agosta and the University of Milan with Professor Daniela Galimberti of the Department of Biomedical, Surgical and Dental.
PCA can affect 10% of Alzheimer’s patients
Scientists studied data from 1,092 PCA patients from 16 different countries around the world and found that, on average, the syndrome begins to affect patients at the age of 59 years, about 5-6 years earlier than most patients affected by the most common form of Alzheimer’s. In the work it was seen that approximately 94% of patients with PCA had Alzheimer’s disease while the remaining 6% were affected by conditions such as Lewy bodies and frontotemporal dementia.
It was not possible to establish the number of people affected by posterior cortical atrophy, but researchers estimate that they may raccount for up to 10% of all Alzheimer’s cases. The authors of the work hope that greater awareness of the syndrome will help doctors diagnose it earlier and encourage researchers to include patients affected by posterior cortical atrophy in Alzheimer’s clinical trials. One thing we discovered from our study – underlines Gil D. Rabinovici, one of the authors of the work and director of the Alzheimer’s Disease Research Center at the University of California – is that when the disease is diagnosed, patients have been suffering from it for many years and so there is much work to be done to raise awareness of the syndrome.
60% of patients are women
The study, which began in 2021, found that PCA is diagnosed on average only four years after the onset of visual symptoms, when signs of memory loss also begin to appear. The progression of the disease is variable: some patients experience memory decline as early as one or two years after the onset of visual symptoms. Research also found that PCA patients had accumulations of plaques of amyloid protein and tau protein like those observed in the most common form of Alzheimer’s, but in a different area of the brain, namely in the back, in the areas responsible for processing visual information. For unclear reasons, a particularly high number of female patients: approximately 60%.
The most common first symptoms concern the difficulty reading and driving. Motorists suffering from PCA have difficulty judging distances. Others have trouble reading at night or distinguish stationary objects and moving objects or they cannot perceive more than one object at a time. Some patients experience hallucinations. Other symptoms may include difficulty doing math calculations or spelling, and many people with posterior cortical atrophy experience anxiety, probably because they know something is wrong. These patients report that they do not see objects in one area of the visual field, that they do not recognize multiple objects at the same time and often do not perceive the distances between one object and another, all situations that have nothing to do with ocular function. Paolo Nucci, Full Professor of Ophthalmology at the University of Milan and department colleague of one of the authors of the study, Daniela Galimberti. In the early stages of posterior cortical atrophy, most people do not have markedly impaired memory, but memory may be impaired in later stages.
The path to diagnosis
Since the first symptoms are visual, patients initially go to a general practitioner, then to an optician-optometrist, subsequently to an ophthalmologist and only finally to a neurologist. Diagnosis is now possible with tests for cognitive abilities or instrumental examinations such as brain magnetic resonance imaging (MRI) or computerized tomography (CT). The first medical check-up for a non-specific visual symptom rightly takes place with an ophthalmologist – underlines Paolo Nucci, who is also President of the Italian Society of Pediatric Ophthalmology and Strabismus – who certifies that the eye, from a functional point of view, has normal capabilities and there are no problems of image doubling or alterations of the visual field which can justify misperceptions, that is, situations in which visual perception is altered. Generally, most ophthalmologists, during the visit, immediately understands whether the visual disperceptions are of a peripheral nature, therefore ocular, or if the disperceptions are of a central nature, therefore of a neurological area. It’s good that there is close collaboration between the ophthalmologist and the neurologist. Be careful of too much alarmism: some of these symptoms may be linked to vascular lesions in the posterior area of the brain.
How to relieve symptoms
Like Alzheimer’s There is no definitive cure for posterior cortical atrophy but vision impairment services can help these patients. To make it easier to see, you can read books with larger print, use more powerful and better lighting in your home and highlight irregular surfaces, such as stairs, with fluorescent adhesive tape. Some patients may benefit from treatments aimed at improving Alzheimer’s symptoms such as cholinesterase inhibitors or NMDA receptor antagonists. However, early identification of PCA could have important implications for the treatment of Alzheimer’s disease, said Renaud La Joie, a neurologist and first author of the study. Consequently, these patients could also be candidates for anti-amyloid therapies currently used only in the United States or for anti-tau therapies, currently in an experimental phase.
The case of Terry Pratchett
Posterior cortical atrophy was first described in medical literature in just five patients in 1988, but for a long time the syndrome was not well understood and experts around the world did not use the same diagnostic parameters. Only in 2017 did scientists agree on a single description of the condition, with a publication in the journal Alzheimer’s & Dementia. The little knowledge about the disease is due to British writer Terry Pratchett, author of the Dissworld series, died in 2015who in 2007 announced that he had been diagnosed with the rare form of Alzheimer’s linked to posterior cortical atrophy.
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February 7, 2024 (modified February 7, 2024 | 09:47)
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