What is Posterior Cortical Atrophy?
Posterior cortical atrophy (PCA), also known as Benson’s syndrome, is a rare degenerative brain and neurological disorder caused due to a gradual and progressive deterioration of the cortex (the outer layer of the brain) at the back (posterior regions) of the brain. This ailment usually affects eyesight and the ability to process visual and spatial information.
What Causes PCA?
It is unclear whether posterior cortical atrophy is a distinct disorder or a possible variant of Alzheimer’s disease. In many people with PCA, the affected parts of the brain exhibit the presence of amyloid plaques and neurofibrillary tangles, which is similar to Alzheimer’s disease but in a different area of the brain. However, in some people, the brain changes are similar to other diseases like Lewy body dementia or a type of Creutzfeldt-Jakob disease. Alzheimer’s disease typically occurs at age 65 or above, while PCA occurs between 50 and 65.
According to researchers, approximately 5% of people diagnosed with Alzheimer’s have PCA. However, because PCA is not often recognized or diagnosed, the actual percentage may be as high as 15%.
Symptoms of PCA
The symptoms of PCA and its progression vary from individual to individual. The most common symptoms are related to the deterioration of the posterior cortex, the part of the brain involved in the processing of visual information. Neurological damage results in the gradual development of difficulties with visual tasks such as:
- Trouble reading a line of text
- Incorrectly judging distances
- Difficulty differentiating between stationary and moving objects
- Inability to distinguish more than one object at a time
- Difficulty identifying and using everyday objects
- Problem with spelling or mathematical calculations
Many people with posterior cortical atrophy may also experience the following behavioral symptoms:
People with PCA generally do not exhibit a considerably reduced memory in the early stages of the disease. However, it can affect the memory in later stages.
Posterior cortical atrophy is an unusual and rare disorder and, therefore, misdiagnosis is common. Since the eyesight problems are the initial symptoms, most people with PCA seek the advice of an ophthalmologist, who may perform regular eye examinations with their usual tests. Cortical brain dysfunction is not initially considered to be the cause of the symptoms.
Currently, there are no diagnostic tests to precisely diagnose PCA. For diagnosis, doctors use a combination of tests, including blood tests, neuropsychological tests, neurological examinations, and brain scans (MRI and PET scans). They also conduct ophthalmology examinations to determine whether the eyesight and vision problems are due to any other condition besides PCA. Finally, the disease is diagnosed by ruling out other possible explanations for symptoms.
The gradual emergence of visual symptoms with retention of normal eye function and memory are characteristic features that the physicians occasionally observe for diagnosis. Furthermore, the age of onset of PCA (50 to 65 years) also provides a clue about the disease. The diagnosis should rule out the chance that the symptoms are due to a stroke, tumor, or other recognizable disorder.
Treatment of PCA
No treatments are currently known to slow the progression of posterior cortical atrophy. Since it resembles Alzheimer’s disease in some people, it is suggested that the medications used for temporary treatment of Alzheimer’s symptoms may be effective in treating PCA, but it is not proven. Some patients may temporarily treat symptoms such as anxiety or depression, but the overall risks or benefits of such treatments are unidentified.
Alzheimer’s Disease and Posterior Cortical Atrophy
Discussion is ongoing in the field to determine whether posterior cortical atrophy should be regarded as a subtype of Alzheimer’s disease or a separate disorder. Brain imaging suggests that the posterior cortex in PCA patients is thinner than in healthy people of the same age, indicating a decreased brain volume in the former. Moreover, although the diseases often overlap, the brains of PCA patients show degeneration in different portions than those of patients with typical Alzheimer’s disease.
Similar to Alzheimer’s disease, the cause of PCA is still not known. There are no known genetic factors or mutations that can cause PCA. It is also unclear whether the risk factors of PCA are the same as Alzheimer’s disease.