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The authors’ observations
A patient such as Ms. D who lives in a minimally supportive environment and has paranoid delusions could fabricate an explanation for what she perceives as family members’ incongruent behavior. She could create a reality in which these relatives are impostors.
Although this behavior is not unusual, Ms. D’s extreme reaction toward her siblings suggests Capgras syndrome, a rare misidentification disorder (Box). The syndrome is often missed in clinical practice, and its prevalence has not been quantified.
Capgras syndrome is seen most often in patients with paranoid schizophrenia—the highest functioning and most preserved schizophrenia patients. This association may indicate that both neurologic dysfunction and psychological background are necessary to produce the syndrome.
The belief that family members are impostors could point to a conspiracy theory or paranoid delusion. Ms. D’s suspicion and distrust toward her older brother indicate a paranoid state, and her other delusions—such as her belief that others are stalking her—suggest that her Capgras symptoms are another manifestation of paranoia.
Capgras syndrome—named for Jean Marie Joseph Capgras, a French psychiatrist who first described the disorder—is characterized by paranoid delusions that close friends or relatives are impostors or “doubles” for the family member/friend or are somehow feigning their identity.
Depersonalization and derealization symptoms are common, as is inability to endorse the verity of another’s identity. Misidentifications—defined as misperceptions with delusional intensity—can also involve people who do not prompt negative or ambivalent feelings or even inanimate objects.
Capgras syndrome may be neurologically and structurally similar to prosopagnosia—which describes inability to recognize familiar faces—but may also be a variation of a paranoid delusion in which the patient seeks to explain affective experiences. The disorder’s coexistence with paranoid delusions also suggests an association with schizophrenia.
For Ms. D, structural brain deficits probably interacted with her psychosocial milieu to create Capgras delusions, though we did not perform confirmatory brain imaging or functional neurologic testing. Whereas right cortical lesions might impair recognition while preserving familiarity, Capgras syndrome preserves recognition but deadens the emotion that makes faces seem familiar. When focal lesions are found to cause Capgras delusion, however, the right hemisphere—specifically the frontal cortex—usually is affected.2,3
Table
Proposed causes of Capgras syndrome
Physiologic |
Frontal lobe damage may distort visual stimuli monitoring, thus impairing facial recognition.4 |
Disruption of neuronal connections within the right temporal lobe scrambles memories needed for facial recognition.5 |
Neurologic |
Disconnection between brain hemispheres lead to cognitive but not affective recognition.6 |
Bifrontal pathology or other organic cause blurs “judgment of individuality or uniqueness,” as in prosopagnosia.3 |
Dorsal pathway impairment alters affective response to faces.7 |
Dissociation in the amygdala may distort affective response to faces.8 |
Psychological* |
In depression, misidentification develops secondary to rationalizing feelings of guilt and inferiority.9 |
“Two-armed recognition”—one automatic and almost instantaneous, the other attentive and mnemonic—begins to falter.10 |
Suspicion, preoccupation with details leads to “agnosia through too great attention.”11 |
Avoidance of unconscious desires leads to recognition problems.12 |
Patient “projects and splits” family member into two persons; directs love toward real person and hate toward imagined impostor.13 |
In schizophrenia, world is viewed through primitive mechanisms, such as doubles and dualism.14 |
*Dependent on psychiatric comorbidity |
The authors’ observations
When interviewing a patient with paranoid delusions, get as much detail as possible about his or her close relationships. Try to interview one or two family members or friends. The information can help determine whether Capgras symptoms underlie paranoia.
Brain imaging might uncover pertinent abnormalities, but the cost could outweigh any benefit. No evidence supports use of CT to diagnose Capgras syndrome. Some evidence supports use of brain MRI, but more research is needed.
No specific treatment exists for Capgras delusions apart from using antipsychotics to treat the psychosis based on clinical suspicion and constellation of symptoms.
Studies have shown no difference in response to atypical antipsychotics between patients with schizophrenia and comcomitant Capgras symptoms and those with schizophrenia alone. In clinical practice, we have found that treating Capgras symptoms does improve schizophrenia’s course.
Adjunctive psychotherapy has not been studied in Capgras syndrome, and directed, insight-guided therapy might not resolve deeply rooted delusions for some patients. With Ms. D, however, “talk therapy” helped us build rapport and gave us insight into her strained familial relationships. Establishing a therapeutic alliance with the patient and encouraging healthy relationships with his or her family and friends can mitigate the effects of Capgras paranoia.