Alzheimer’s is typically seen as a memory-robbing disease that presents initially as forgetfulness, difficulty remembering recent events, and increased confusion.
However, some people may present with a lesser-known early warning sign of dementia in the form of vision problems such as trouble judging distances, distinguishing between moving and stationary objects, and writing.
These can go undiagnosed for years if the person only sees their eye doctor, as too few providers know to look for it.
Doctors are seeking to change that with the first-ever large-scale international study on the phenomenon known as posterior cortical atrophy (PCA) led by the University of California San Francisco. For the research, the team looked at the medical files of more than 1,000 PCA patients from 16 different countries.
The visual-spatial symptoms of PCA begin affecting patients about five or six years earlier than patients with the more common form of Alzheimer’s.
And while the firm number of people with PCA has not been established, researchers estimate that the variant may account for up to 10 percent of Alzheimer’s cases – putting the number of Americans with the condition close to 700,000.
In the first large-scale study on posterior cortical atrophy, a subtype of Alzheimer’s, researchers estimated that the little-investigated condition may account for up to 10 percent of Alzheimer’s cases
PCA is a specific subtype of Alzheimer’s disease, and not all Alzheimer’s patients will experience the symptoms, which also include difficulty with reading and math, using everyday objects, judging distances, and recognizing faces. Memory problems may become more apparent as the disease progresses.
The average age when symptoms typically manifest is 59 years old, six years before the average age at which Alzheimer’s disease is diagnosed.
The symptoms can affect people with no other memory problems, making some think the issues are not neurological. Worsening vision is a side effect of the general aging process, and many adults around in their 50s and 60s are likely to attribute their vision disturbances to their advancing age, and rather than seek out medical care, opt for glasses.
A lot of time may have elapsed until they finally see an ophthalmologist, who would, upon noticing abnormalities in a person’s vision test results, refer them to a neurologist who can identify the problem.
The average time it takes from first experiencing the atypical visual symptoms to finally receiving a diagnosis is just under four years.
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.’
In the study, researchers measured levels of two hallmarks of Alzheimer’s disease – tau and amyloid proteins. Amyloid beta accumulates in the brain, forming plaque deposits that are believed to trigger inflammation in the body and drive the disrupted communication between brain cells.
Tau, meanwhile, typically helps stabilize the internal structure of nerve cells in the brain. But in the case of Alzheimer’s, abnormal chemical changes cause tau to detach from nerve cells and reattach to other tau proteins, forming threads that eventually become tangles.
People with PCA had similar levels of tau and amyloid plaques in their brains as those with the more common form of Alzheimer’s.
While there is no known cure, the common pathologies that Alzheimer’s and PCA share mean that PCA patients may benefit from participating in a clinical trial for one of several medications in the pipeline or talking to their provider about the Food and Drug Administration-approved anti-amyloid drug lecanemab.
Better understanding of PCA is ‘crucial for advancing both patient care and for understanding the processes that drive Alzheimer’s disease,’ said senior author Dr Gil Rabinovici, director of the UCSF Alzheimer’s Disease Research Center.
He added: ‘It’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% of patients with PCA were women—better understanding of why they appear to be more susceptible is one important area of future research.’
Their research was published in the journal Lancet Neurology.