New symptoms such as failing to identify more than one object at a time and a “space perception deficit” could be the first signs of Alzheimer’s disease, a new study has found.
Posterior cortical atrophy (PCA), is a diagnosis for those who struggle with judging distances, distinguishing between moving and stationary objects and completing tasks like writing and it overwhelmingly predicts Alzheimer’s.
In the latest study from researchers at the University of California, San Francisco, some 94 per cent patients with PCA had Alzheimer’s pathology . Most patients with PCA have normal cognition early on, but by the time of their first diagnostic visit, an average 3.8 years after symptom onset, mild or moderate dementia was apparent with deficits identified in memory, executive function, behavior, and speech and language , according to the researchers’ findings.
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According to the team of international researchers, these new PCA symptoms, relating to sight and space detection, are visible signs of Alzheimer’s.
These symptoms occur in up to 10 per cent of cases, as concluded for a study that included data from more than 1,000 patients at 36 sites in 16 countries, as per the Lancet Neurology .
At the time of diagnosis, 61 per cent of participants demonstrated “constructional dyspraxia,” which looked like patients being unable to copy or construct basic diagrams or figures.
Another 49 per cent had a “space perception deficit,” meaning they struggled to identify the location of something they saw; and 48 per cent had “simultanagnosia,” an inability to visually perceive more than one object at a time.
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On top of this, 47 per cent found it hard to process basic math and 43 per cent struggled to read. Marianne Chapleau, PhD, of the UCSF Department of Neurology said: “We need more awareness of PCA so that it can be flagged by clinicians. Most patients see their optometrist when they start experiencing visual symptoms and may be referred to an ophthalmologist who may also fail to recognize PCA.
“We need better tools in clinical settings to identify these patients early on and get them treatment. The average age of symptom onset of PCA is 59, several years younger than the typical memory symptoms of Alzheimer’s. This is another reason why patients with PCA are less likely to be diagnosed.''
Renaud La Joie, PhD, also of the UCSF Department of Neurology and the Memory and Aging Center said identifying PCA early may have important implications for Alzheimer’s treatment, said co-first author.
In the study, levels of amyloid and tau, identified in cerebrospinal fluid and imaging, as well as autopsy data, matched those found in typical Alzheimer’s cases. As a result, patients with PCA may be candidates for anti-amyloid therapies, like lecanemab (Leqembi), approved by the U.S Food and Drug Administration in January 2023, and anti-tau therapies, currently in clinical trials, both of which are believed to be more effective in the earliest phases of the disease, he said.
“Patients with PCA have more tau pathology in the posterior parts of the brain, involved in the processing of visuospatial information, compared to those with other presentations of Alzheimer’s. This might make them better suited to anti-tau therapies,” he said.
La Joie added that patients have mostly been excluded from trials, since they are “usually aimed at patients with amnestic Alzheimer’s with low scores on memory tests. La Joie said: “However, at UCSF we are considering treatments for patients with PCA and other non-amnestic variants.”
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Gil Rabinovici, MD, director of the UCSF Alzheimer’s Disease Research Center said: “Better understanding of PCA is “crucial for advancing both patient care and for understanding the processes that drive Alzheimer’s disease. t’s critical that doctors learn to recognize the syndrome so patients can receive the correct diagnosis, counseling and care.
“From a scientific point of view, we really need to understand why Alzheimer’s is specifically targeting visual rather than memory areas of the brain. Our study found that 60 per cent of patients with PCA were women — better understanding of why they appear to be more susceptible is one important area of future research.”
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