Vision Failure Leads to Wrong Diagnosis: Posterior Cortical Atrophy, Not Depression

She began having difficulty reading memos a few months earlier. She thought perhaps her glasses needed adjustment. A trip to the optometrist led to a new pair of glasses, only slightly different than before.


The new glasses didn’t help.

She still had trouble reading memos, even those she created and wrote herself. As a result, she couldn’t correct typos and other errors. The spell checker highlighted so many words, and it was so hard for her to understand the problem, that she turned it off.

Her adult daughter urged her to go to an ophthalmologist, who had more training in vision disorders than the optometrist. The ophthalmologist ordered a CT scan of her brain. Nothing unusual was found.

Going to the office became so uncomfortable she came up with excuses to stay home. It became hard for her to read menus, even signs, so she stayed away from all her social activities as well.

 

Because her job caused her frustration and sadness, and she withdrew socially, and the ophthalmologist found no abnormality, her physician thought the problem was psychosomatic, the result of depression. She prescribed an antidepressant for her patient.

The antidepressant didn’t help.

In the next months, she had developed a number of signs.

  • Visual agnosia (the inability to recognize familiar objects)
  • Visual apraxia (the inability to perform movements that depended closely on vision, such as passing an object through a ring)
  • Simultanagnosia (while recognizing individual objects, the person cannot integrate the objects into a whole image, so doesn’t recognize or identify the image)
  • Prosopagnosia (inability to recognize faces, probably because the whole face image is not perceived due to simultanagnosia, so it can’t be compared to known images)
  • Acalculia (inability to perform arithmetic)
  • Inability to put her clothes on
  • Inability to recognize highway signs
  • Hallucinations occur in about 25%

By this time, she did have some short term memory loss, but the visual signs were much more prominent. A local neurologist who examined her said she had Alzheimer’s dementia, and prescribed Aricept, a drug for Alzheimer’s.

The Aricept didn’t help.

Her family took her to a specialist center. A PET study of her brain was done. (PET studies are similar to CTs, but provide not only information about structure, but also about function.) The PET study was consistent with the center’s clinical diagnosis, posterior cortical atrophy. (It’s also sometimes called Benson’s Syndrome.)

What is Posterior Cortical Atrophy?

Posterior Cortical Atrophy (PCA) is a brain condition in which cells in a part of the brain die and that part shrinks (atrophies). The part of the brain affected is in the back (posterior) and is responsible for visual processing.

Visual processing is tying images to memories to make sense of them. It is a process that is separate from simply registering an image. Registering an image is transferring its representation from the retina in the eye to the occipital cortex in the back of the brain. Visual processing takes place through at least two main streams from the occipital cortex, and can include over half the entire brain cortex.

An example of visual processing is putting letters together to make understandable words. Another is prosopagnosia. In this case, the patient developed a problem recognizing her daughter, except by voice. She could see parts of her daughter’s face, but could not integrate the image to match it with images in her memory. Sometimes she would ask where her daughter was, when her daughter was standing in the room with her.

What Causes PCA?

Any of the conditions that can cause dementia can cause PCA. The most common appears to be Alzheimer’s. Dementia with Lewy Bodies and Creutzfeldt Jacobs disease have also been implicated.

Treatment

There is no cure for PCA. An understanding of the condition and support for the affected person is recommended. Memory loss usually appears, and planning for that is important.