In Alzheimer’s disease, around ten percent of those affected develop noticeable visual impairments in the form of so-called posterior cortical atrophy long before the typical symptoms of the disease appear. This finding could enable a much earlier diagnosis and certain therapeutic approaches also appear to be particularly suitable for those affected.
An international research team led by Dr. In a review, Marianne Chapleau from the Memory and Aging Center at the University of California San Francisco (UCSF) assessed the connections between posterior cortical atrophy and Alzheimer’s disease based on, among other things, biomarkers, clinical symptoms and neuropathological factors. The results are published in the specialist magazine “The Lancet Neuroloy”.
Impaired visual-spatial perception
Posterior cortical atrophy is characterized by disturbances in visual-spatial perception and has already been linked to neuropathological features of Alzheimer’s disease in previous studies, the researchers explain.
With posterior cortical atrophy, those affected have difficulty estimating distances, distinguishing between moving and stationary objects, and completing tasks such as writing or locating a dropped object – despite otherwise normal vision, says Dr. Chapleau.
Connections with Alzheimer’s examined
In order to specifically assess the possible connections between posterior cortical atrophy and Alzheimer’s disease, the research team identified the research papers published to date and contacted the corresponding authors or the management of the relevant research centers.
They obtained the individual data (published and unpublished) of 1,092 people from 36 research centers in 16 countries worldwide. Inclusion criteria were a diagnosis of posterior cortical atrophy and availability of Alzheimer’s disease biomarkers.
The researchers recorded demographic, clinical and neuropathological data and evaluated CSF examinations and neuroimaging recordings.
94 percent developed Alzheimer’s
It became clear that most participants with posterior cortical atrophy initially had normal cognitive abilities, but as the disease progressed, 94 percent developed Alzheimer’s pathology and the remaining six percent developed other forms of dementia, the team reports.
According to the researchers, the amyloid and tau levels found in the cerebrospinal fluid and in imaging procedures as well as in autopsy data matched those of typical Alzheimer’s cases.
On average, 3.8 years after the onset of visual symptoms, mild or moderate dementia with deficits in the areas of memory, executive function, behavior, and language and speech developed, the experts continued.
Hope for improved treatment
Overall, it has become clear that posterior cortical atrophy can form an early form of dementia that is very specific to the underlying Alzheimer’s pathology. According to the researchers, early detection of posterior cortical atrophy could also enable significant improvements in Alzheimer’s treatment.
If necessary, anti-amyloid therapy (for example with Lecanemab, approved by the US Food and Drug Administration (FDA) in January 2023) or anti-tau therapy (currently in clinical trials) is an option for those affected, because it is assumed that that they are more effective in the earliest stages of the disease.
Additionally, those with posterior cortical atrophy show more tau pathology in the posterior parts of the brain involved in processing visuospatial information, which may make them more suitable for anti-tau therapies, according to co-first author Dr. Renaud La Joie of the Memory and Aging Center at UCSF.
Better understand posterior cortical atrophy
According to Dr. According to Chapleau, there is an urgent need for greater awareness of posterior cortical atrophy and better tools in the clinical setting to identify those affected early and treat them.
Most people probably go to an ophthalmologist’s office when they first notice visual problems and the posterior cortical atrophy may not be recognized as such, reports the expert.
Here, a better understanding of posterior cortical atrophy is crucial both for patient care and for understanding the processes underlying Alzheimer’s disease, adds Dr. Gil Rabinovici, director of the UCSF Alzheimer’s Disease Research Center.
“From a scientific perspective, we really need to understand why Alzheimer’s disease specifically attacks the visual areas of the brain and not memory,” said Dr. Rabinovici. Further studies are urgently needed here. (fp)