Identified in 1923 by the French psychiatrist Joseph Capgras, this syndrome is characterized by the erroneous certainty that a person important to the patient has been replaced by an imposter.
Substitution mainly affects “people to whom the patient is linked by an intense emotional feeling”, confirm for True Medical Dr. Casseron, neurologist. Most often, this is the spouse or a family member.
In rarer cases, this belief extends to pets, items of high sentimental value, or even voices. The patient is then convinced that he is hearing an imposter.
A break between face recognition and emotion
For a long time, Capgras syndrome was considered a purely psychiatric manifestation, close to schizophrenic delusions.
Neuroscience then revealed a very specific organic origin: lesions in the frontal lobes and the limbic system, disrupting memory and the perception of reality.
“There is an area dedicated to face recognition called the fusiform gyrus, in the right hemisphere. In Capgras syndrome, there is a bundle that connects this fusiform gyrus to the amygdala, the emotional processing area, and this area becomes damaged.” explains the neurologist.
The mechanism is similar to a computer bug in the brain.
“It’s a bit as if there was a disconnect between the software that allows you to recognize someone and the software that allows you to verify that it’s a person you know and like. Normally, when you see a loved one, you open a sort of “file” stored in your memory. Patients with Capgras syndrome open a new file each time: they see the physical resemblance, but no longer have the emotional recognition”.
Various neurological and psychiatric causes
The syndrome rarely manifests itself in isolation. It is almost systematically grafted onto pre-existing pathologies. “It is a syndrome that we encounter relatively infrequently in neurology, but which is part of a broader pathology.confirms Dr. Casseron.
“It is mainly seen in neurodegenerative diseases, such as diffuse Lewy body disease or Alzheimer’s disease, but it can also be described after head trauma or certain strokes.
In addition to these neurological disorders, delusions of lookalikes sometimes occur in the context of schizophrenia, epilepsy or pituitary tumors.
This disorder should not be confused with prosopagnosia (the pure and simple inability to identify a face) nor with Frégoli syndrome. “In Frégoli syndrome, it is not the idea that a loved one has been replaced by a double, but that a known person changes their face and disguises themselves to persecute you“, underlines the neurologist.
A fluctuating and trying daily life for those around you
One of the most destabilizing aspects of Capgras syndrome is its unstable nature. The conviction of imposture is not always continuous. “There is a fluctuating side: the person can sometimes behave normally with their partner, then the next day no longer recognize them and want to run away, thinking that it is a disguise.notes Dr. Casseron.
This unpredictability makes the situation complex for the family and caregivers, who are often helpless when faced with a loved one who rejects them while recognizing their physical traits. Under the influence of anxiety and the conviction of being faced with a threatening stranger, some patients can also develop violent behavior.
Offering material evidence, such as wedding photos or shared memories, generally proves ineffective: the patient concedes that the photo represents their “real” spouse, but persists in saying that the person in front of them is a double.
What treatment for Capgras syndrome?
There is no specific treatment to cure Capgras syndrome. Management relies entirely on treatment of the underlying disease.
If neuroleptics are sometimes prescribed to calm aggression or delusional conviction, their effectiveness remains limited and their side effects are significant. “We cannot really treat the syndrome itself. When you give neuroleptics, you risk dumbing down patients. We sometimes use molecules like clozapine or quetiapine, but these treatments are not absolutely effective.“, concludes Dr Wilfrid Casseron.
Faced with this therapeutic impasse, the role of the medical profession consists above all of supporting caregivers. Explaining the neurological nature of the disorder, making them understand that these rejections are not intentional and teaching them to defuse anxiety attacks constitute today the only levers to soften the daily lives of families.