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Eye Problem That May Indicate Alzheimer’s Needs Better Diagnosis, Say Researchers

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In a study published in Lancet Neurology, a team led by UC San Francisco has unveiled crucial insights relating to posterior cortical atrophy (PCA), a condition that often signals the onset of Alzheimer's disease. This study, remarkable for its scale and international collaboration, collected data from over 1,000 patients across 36 sites in 16 countries, shedding light on a lesser-known aspect of Alzheimer's that primarily affects visual processing.

A commonly misdiagnosed symptom

PCA is a condition that produces visuospatial symptoms, rather than the typical memory issues associated with Alzheimer's, and is found in up to 10% of Alzheimer’s cases. In the new study, a striking 94% of PCA patients showed Alzheimer’s pathology, with the remainder having pathology indicating Lewy body disease and frontotemporal lobar degeneration. There’s only a 70% prevalence of Alzheimer's pathology in patients presenting with memory loss.

PCA's impact on patients is profound yet often misdiagnosed. Affected individuals struggle with spatial judgment, identifying movement and executing everyday tasks such as retrieving dropped items. Surprisingly, these difficulties occur despite normal eye exams. General cognition is unaffected early in PCA, but mild dementia symptoms often emerge by the time that patients are diagnosed – on average, this is nearly four years after symptoms first emerge. The average age of PCA onset is 59. This is several years younger than linked memory symptoms, which further complicates diagnosis. 

Co-first author Dr. Marianne Chapleau, from UCSF's Department of Neurology, said that better diagnostic tools for PCA are needed. “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,” she said. “We need better tools in clinical settings to identify these patients early on and get them treatment.”

Better diagnosis, better treatment

Dr. Renaud La Joie, Chapleau’s colleague at UCSF and co-first author, said that early PCA detection could improve Alzheimer's treatment. The study found that PCA patients exhibit amyloid and tau levels akin to those in typical Alzheimer's cases, suggesting that they might benefit from emerging anti-amyloid and anti-tau therapies, which are thought to have superior effectiveness when given early in the disease’s course.

This research not only opens new avenues for patient care but also poses crucial questions for the scientific community. Senior author Gil Rabinovici, MD, director of the UCSF Alzheimer’s Disease Research Center, pointed out the necessity to understand why Alzheimer's targets visual rather than memory areas in the brain, noting the higher prevalence of PCA in women as a key area for future research.

Reference: Bejanin A, Villain N. Posterior cortical atrophy: new insights into treatments and biomarkers for Alzheimer’s disease. The Lancet Neurology. 2024;23(2):127-128. doi:10.1016/S1474-4422(23)00501-X

This article is a rework of a press release issued by the University of California San Francisco. Material has been edited for length and content.