Strange visual disturbances occur early in about 10% of Alzheimer’s cases, and when this happens it almost always signals the impending arrival of the disease, a new study finds.
The condition is called posterior cortical atrophy (PCA). It involves a sudden difficulty in performing vision-related tasks — for example writing, judging whether an object is moving or stationary, or easily picking up a dropped item. Everyday tasks like these become difficult despite the fact that a person’s eye exam comes out fine.
“We need more awareness of PCA, so that it can be flagged by clinicians,” said study co-lead author Marianne Chapleau, of the University of California, San Francisco’s department of neurology.
“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 in a UCSF news release. “We need better tools in clinical settings to identify these patients early on and get them treatment.”
To determine just how predictive of dementia PCA might be, Chapleau’s team analyzed data on over 1,000 patients at 36 sites in 16 countries. PCA tended to emerge at a fairly young age — 59, on average.
Patients with PCA often failed to accurately copy simple diagrams, had trouble gauging an object’s location or had difficulty visually perceiving more than one object at a time, the research showed. Math and reading skills also began to falter.
In 94% of cases, people experiencing PCA went on to develop Alzheimer’s disease, the UCSF team found. The remaining 6% developed other dementias such as Lewy body disease or frontotemporal lobar degeneration.
The researchers pointed out that’s far more predictive of dementia than a condition such as memory loss: Only 70% of people with failing memories go on to develop dementia, they said.
Many people may show no cognitive issues when first stricken with PCA, but the study found that by about four years later, mild or moderate deficits in memory, executive function, behavior, and speech and language became apparent.
The findings were published Jan. 22 in The Lancet Neurology journal.
Renaud La Joie, also from UCSF’s department of neurology and the university’s Memory and Aging Center, is first author of the study. He believes that because PCA typically emerges years before actual dementia, it could point to patients who might be helped by newly approved Alzheimer’s medications.
Some of those medications target tau, a protein that builds up in the brains of people with Alzheimer’s disease.
“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 explained.
“It’s critical that doctors learn to recognize the syndrome so patients can receive the correct diagnosis, counseling and care,” added senior study author Dr. Gil Rabinovici, who directs the UCSF Alzheimer’s Disease Research Center.
“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,” he added. “Our study found that 60% of patients with PCA were women — [getting a] better understanding of why they appear to be more susceptible is one important area of future research.”
Find out more about Alzheimer’s disease at the Alzheimer’s Association.
SOURCE: University of California, San Francisco, news release, Jan. 22, 2024
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