Mistaken Identity: A Difficult Problem in Alzheimer's Disease

As many as one in six people with Alzheimer’s disease or other dementias may suffer from delusional misidentification syndromes. This article explores the potential causes and treatments for these unusual conditions that torment people with dementia and those who care for them.

In one of the scariest Terminator movies, a futuristic android weapon gets close to its victims by assuming the appearance and voice of someone familiar. Only those who know of this danger can remain constantly on guard to prevent a malicious imposter’s attack. In another, more heartwarming movie, the amazingly talented Robin Williams assumes a disguise so convincingly that his own family unknowingly embraces him as their beloved nanny, Mrs. Doubtfire. Yet another identity trick is embodied in films such as Jean-Claude Van Damme’s Replicant, in which multiple duplicate clones of a single individual pursue their independent goals. What do all these films have in common? The plot of each depends on a distortion of identity.  In addition, each of these confusing scenarios is identical to actual experiences that torment some people with dementia and those who care for them.

Grouped together as “Delusional Misidentification Syndromes,” these conditions are easier to name than they are to treat. As many as one in six people with Alzheimer’s disease or other dementias may suffer from these delusional syndromes.

Capgras Syndrome

Capgras syndrome, described in 1923 by the psychiatrist whose name it bears, is the false belief that a familiar person has been replaced by a duplicate imposter, usually one with evil intent. This delusion can be a feature of schizophrenia and is also seen in brain disorders including traumatic injury, cerebrovascular disease, epilepsy, and dementia.

Fregoli Syndrome

Fregoli Syndrome, named after a famous actor known for his skill in impersonation, was described in 1927. People with Fregoli syndrome mistake unfamiliar people or places for familiar ones.

Reduplicative Paramnesia

Reduplicative paramnesia was described in 1903 by a neurologist whose name is well known to students of dementia, Arnold Pick. His 67-year-old patient, suffering from dementia, believed Dr. Pick had two duplicate clinics in Prague. People with this syndrome can believe they have encountered multiple people who are different despite their identical appearances and protestations that they are not clones or duplicates.  

What Causes These Delusions?

Researchers continue to debate the cause of these disorders, but they agree that brain disease is an important factor. The right hemisphere, important in the “sense of familiarity,” is affected in some patients. Lesions of the frontal lobes, which help us monitor the accuracy of our memories, have also been implicated. A region of the brain called the perirhinal cortex, involved in familiarity, may be underactive in Capgras syndrome and overactive in Fregoli syndrome, accounting for uncertainty of familiarity in the first condition and false certainty of familiarity in the second. Other brain areas are suspected to play roles as well, such as the fusiform gyrus, involved in face identification. The bottom line in all these conditions is that affected individuals must struggle to explain to themselves the disturbing sense of familiarity or unfamiliarity that seems out of context.

Stressful and Dangerous Complications

Understanding these syndromes is more than an exercise in classification for anyone who lives with a cognitively impaired person! Capgras syndrome can induce a wife to risk her safety by fleeing in the middle of the night from a home she believes to have been invaded by an imposter husband. Homicidal attacks on family members are a rare but dangerous complication of Capgras syndrome.  Fregoli syndrome, too, can lead to danger, for example by inciting a friendly or aggressive assault on an innocent and unsuspecting bystander believed to be a known and feared person in disguise. A person with reduplicative paramnesia faces the stressful problem of deciding who, among a group of identical individuals, is not a confidence-seeking and potentially harmful imposter. Fortunately, aggression is not a very common complication.  Day-to-day management problems are usually more stressful than dangerous.

Treatment Options

Habilitation Therapy

Helping a cognitively impaired person cope with delusional misidentification can be very challenging.  As with other psychotic symptoms, it is safer to try non-medication approaches first unless the false beliefs are causing agitated or dangerous behaviors. Confronting a delusional person with the “truth” is rarely helpful and may increase their fear and distress. On the other hand, the principles of “habilitation therapy” can be applied here, often with greater success. As described by the dementia expert Beverly Moore, habilitation therapy involves entering the world of the person with dementia in order to create positive emotional experiences rather than increased suffering.  There is usually no need to prove the misguided person wrong, a victory that at best will be brief. Instead, try to appreciate how upsetting it is to experience the presence of an imposter or duplicate! Let the person know you realize how upsetting this is, and offer reassurance that you are there to help. If a suspected imposter is present, the problem is sometimes solved by having them leave briefly and return with a warm smile and friendly comment. Voice recognition may be more convincing than visual recognition, so the suspected imposter may succeed at invoking recognition by speaking even before coming into the line of sight: “Hi, honey – It’s your husband, Bob - I’m home!”

Medication

medications may be tried. The cognitive enhancers such as donepezil can occasionally help, but their effectiveness in treating behavioral symptoms is limited. Antidepressants including serotonergic agents or mirtazapine have anecdotally been reported helpful. The typical and atypical antipsychotic medications, including clozapine, have also been reported as beneficial in some cases, but again their effectiveness may be limited and this class of medications carries a warning of increased death risk among individuals with dementia and psychosis.

Misidentification syndromes can be perplexing to health care providers and frustrating to caregivers, but the worst experience must certainly be that of the person whose senses say one thing while their heart says another. Confrontation puts an already confused and frightened person in the situation that a bewildered Margaret Dumont  faces in the movie Duck Soup when she questions  Chico Marx, who is impersonating Groucho Marx’s character. Chico famously responds Well, who ya gonna believe – me or your own eyes?"  

With the approach outlined here and an attitude of compassion and patience, sometimes supplemented with medication, a difficult and potentially antagonistic situation can sometimes be transformed into a cooperative and positive interaction.