Have You Been Replaced by an Imposter?

In my last article I discussed why some people with dementia develop hallucinations and illusions. In this article I will discuss some other disturbing visual problems that can occur in dementia.

Your loved one may think you are someone else, or simply not recognize you at all

Some of the most distressing symptoms that can occur in dementia is if your loved one doesn’t recognize you or thinks that you are someone else. Although incredibly disturbing, remember that it is the dementia that causes these symptoms to occur, usually due to problems with vision or memory or both. One possibility is that your loved one’s representation of you in their memory is from long ago because of the failure of their hippocampus or cortex, and you look different now because you are older. Another possibility is that their representation of you is accurate but their image of you is distorted because of visual impairment. In either case, the image of you that they are seeing doesn’t match their representation of you stored in their memory.

Why might they think you are someone else? If their representation of you is from years earlier—before you had grey hair, for example—it may be that that the image they are seeing of you with grey hair is actually a better match for their representation of their father, and so when they see you they think you are their father. This error would be particularly likely if, because of their memory problems, they think they are young and don’t yet have a spouse or children.

Your loved one may believe that you have been replaced by an imposter

Another distressing symptom that can occur is when your loved one thinks that you have somehow been replaced with an imposter. Although bizarre, this delusion is not uncommon in dementia. Usually it is from a combination of brain problems affecting not only memory and vision but also reasoning and emotion. The dementia damages the connection between the occipital lobes and the brain’s emotional center, the amygdala. So, although the image of you is correctly perceived, the emotional connection to the image is lost and, to your loved one, it is like looking at a stranger who just happens to resemble to you. Does it seem unrealistic that you would be replaced by an imposter? You’re right—that’s why the frontal lobes, the brain’s reasoning center, must also be damaged by the dementia in order for this type of delusion to occur.

When visual symptoms are the first and most prominent problem

Lastly, some individuals with dementia have visual problems as their most prominent symptom, while their other cognitive functions, such as memory, language, and behavior, are more or less OK. If this description sounds like your loved one, you may have heard the term posterior cortical atrophy. Posterior cortical atrophy is not a disease in itself but is a useful way to describe individuals with dementia who have these types of visual problems as their most prominent symptoms. The name comes from the fact that it is the back or posterior part of the brain that is most affected.

Key Question:

Half the time my wife thinks I’m her father or her brother, and the other half she recognizes me—but doesn’t think I’m the real me! What’s going on?

• These disturbing symptoms commonly occur in dementia. The important thing to remember is that they stem from the dementia affecting many parts of the brain at once. We’ll talk about some strategies to help you cope with these problems in later articles. Also make sure that any eye problems are corrected—your loved one will have difficulty recognizing you if they cannot see you clearly.

In my next article I will begin to discuss why problematic behaviors occur in dementia.

© Andrew E. Budson, MD, 2019, all rights reserved.