Posterior cortical atrophy or APC, which includes a huge variety of visuospatial symptoms, appears to be one of the warning signs of Alzheimer’s disease. This was revealed by a study by an international group of researchers, led by UC San Francisco, published in The Lancet Neurology. The results showed that symptoms occur in up to 10% of Alzheimer’s disease cases. The scientists, who used data from more than 1,000 patients at 36 sites in 16 countries for the study, found that posterior cortical atrophy overwhelmingly predicts Alzheimer’s.
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Research
Approximately 94% of APC patients had Alzheimer’s disease, while the remaining 6% had conditions such as Lewy body disease and frontotemporal lobar degeneration. In contrast, other studies have shown that 70% of patients with memory loss had pathology typical of Alzheimer’s disease.
“Unlike memory problems, patients with APC have difficulty defining distances, distinguishing between moving and stationary objects, and completing tasks such as writing and retrieving a dropped object, despite a normal eye exam,” he said. explained Marianne Chapleaufrom the Ucsf Department of Neurology, the Memory and Aging Center and the Weill Institute for Neurosciences and co-author of the study.
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Most APC patients initially have normal cognition, but by the time of the first diagnostic visit, an average of 3.8 years after the onset of symptoms, mild to moderate dementia with identified deficits in memory has been found. , executive function, behavior and language.
Constructive dyspraxia
At the time of diagnosis, 61% had constructional dyspraxia, which is the inability to copy or construct basic diagrams or figures; 49% had a spatial perception deficit, which translates into difficulty identifying the position of what is seen; and 48% had simultanagnosia, which is the inability to visually perceive more than one object at a time. Furthermore, 47% encountered difficulties in carrying out basic mathematical calculations and 43% in reading.
“We need greater awareness of APC so that it can be easily reported by patients and recognized by doctors,” said Chapleau. “Most patients turn to an optometrist when they begin to experience visual symptoms and are often referred to see an ophthalmologist, who may not even recognize APC. We need better tools in the clinical setting to identify these patients early and treat them.
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The average age
The average age of onset of APC symptoms is 59 years, several years younger than that of Alzheimer’s. This is another reason why APC patients are less likely to be diagnosed.”
“Early identification of APC could have important implications for the treatment of Alzheimer’s,” he said Renaud LaJoie, also from the Ucsf Department of Neurology and the Memory and Aging Center and first author of the study. In the research, levels of amyloid and tau, identified in cerebrospinal fluid and imaging, as well as in autopsy data, matched those found in typical cases of Alzheimer’s. Consequently, patients with Apc may be candidates for anti-amyloid therapies, such as lecanemab, approved by the US Food and Drug Administration in January 2023, and anti-tau therapies, currently in clinical trials, both considered more effective in early stages of the disease.
“Patients with APC have a greater extent of 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 disease – noted La Joie – this could make them more suitable for anti-tau therapies. tau. Apc patients have mostly been excluded from trials, as these are usually aimed at amnestic Alzheimer’s patients with low memory test scores. However, at Ucsf we are evaluating treatments for patients with Apc and other non-amnestic variants “.
“A better understanding of APC is crucial to advancing both patient care and understanding of the processes that drive Alzheimer’s disease,” he noted. Gil Rabinovici, director of the UCSF Alzheimer’s Disease Research Center and senior author of the study – it is critical that doctors learn to recognize the syndrome so that patients can receive the correct diagnosis, advice and care. From a scientific point of view, we need to understand why Alzheimer’s specifically affects visual brain areas rather than memory areas. The study – he concluded – found that 60% of patients with APC were women: better understanding why they seem to be more susceptible is an important area of future research”.