Alzheimer’s researchers have discovered that some people may be experiencing a lesser-known early warning sign of the syndrome that affects vision, as they called for greater awareness of the symptoms.
Those with the condition may begin to have vision problems, such as difficulty judging distances, distinguishing between moving and stationary objects, as well as writing.
As too few providers currently know how to look for it, these cases can remain undiagnosed for years.
Research led by the University of California San Francisco, the first-ever large-scale international study on the condition known as posterior cortical atrophy (PCA), examined the medical files of over 1,000 PCA patients across 16 different countries.
The average age that symptoms typically begin to appear is 59 years old, the study published this week in Lancet Neurology found, six years before the average age at which Alzheimer’s disease is diagnosed.
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People can experience the symptoms with no other memory problems, leading some to assume that the issues are not neurological, and the study’s authors have urged for better clinical tools to be introduced to identify the condition earlier.
The visual-spatial symptoms of PCA begin to emerge about five or six years earlier than those with a more common form of Alzheimer’s.
Though it has not been firmly established how many people have the condition, researchers estimate that it may represent up to 10 percent of Alzheimer’s cases.
PCA is a specific subtype of Alzheimer’s, and the symptoms, which also include difficulty doing maths, using everyday objects, and recognizing faces, won’t be experienced by all Alzheimer’s patients.
As the disease progresses, memory problems may also become more apparent.
Worsening vision is common as we get older, and many adults around in their 50s and 60s are likely to put problems with their vision down to their advancing age, and opt for glasses rather than a medical assessment.
On average it takes just under four years for people experiencing the atypical visual symptoms to finally get a diagnosis.
Dr Marianne Chapleau, a co-author of the paper and researcher at the UCSF Department of Neurology, the Memory and Aging Center, 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.”
Researchers measured levels of tau and amyloid proteins, two hallmarks of Alzheimer’s disease.
Amyloid beta builds up in the brain, forming plaque deposits scientists believe cause inflammation in the body and drive disrupted communication between brain cells.
Meanwhile, Tau typically helps to stabilize the internal structure of nerve cells in the brain.
However, with Alzheimer’s cases, abnormal chemical changes result in tau detaching from nerve cells and reattaching to other tau proteins, creating threads that become tangled.
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People with PCA were found to have similar levels of tau and amyloid plaques in their brains as those with the Alzheimer’s in its more common form.
Senior author Dr Gil Rabinovici, director of the UCSF Alzheimer’s Disease Research Center, said building a greater understanding of PCA is “crucial for advancing both patient care and for understanding the processes that drive Alzheimer’s disease.”
“It’s critical that doctors learn to recognize the syndrome so patients can receive the correct diagnosis, counseling and care,” he added.
“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 percent of patients with PCA were women—better understanding of why they appear to be more susceptible is one important area of future research.”
Early identification of the conditions may also have important implications for Alzheimer’s treatment, the study’s first author Renaud La Joie, Ph.D. said.
As the research found levels of amyloid and tau in PCA patients matched those found in typical Alzheimer’s cases, people with the rarer condition may be candidates for anti-amyloid therapies, like lecanemab (Leqembi), as well as anti-tau therapies, which are currently in clinical trials, both of which are thought to be more effective in the earliest phases of the disease, Le Joi 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,” he said.
“This might make them better suited to anti-tau therapies.”
He added that in the past, patients have mostly been excluded from trials, because they are “usually aimed at patients with amnestic Alzheimer’s with low scores on memory tests. However, at UCSF we are considering treatments for patients with PCA and other non-amnestic variants.”
