What is the treatment for Capgras syndrome (third man syndrome)?

Treatment of Capgras Syndrome

Antipsychotic medication, particularly pimozide or risperidone, is the first-line treatment for Capgras syndrome, with risperidone recommended at a starting dose of 0.25mg/day (maximum 2mg/day) for most effective symptom management. 1, 2

Understanding Capgras Syndrome

Capgras syndrome is a delusional misidentification disorder characterized by the false belief that a person, usually someone close to the patient, has been replaced by an identical-looking impostor. It can occur in several forms:

• Classic Capgras: Belief that a loved one has been replaced by an impostor
• Reverse Capgras: Belief that oneself has been replaced by an impostor 3
• Zoocentric Capgras: Belief that a pet has been replaced by another identical animal 4

Etiology and Associated Conditions

Capgras syndrome is most commonly associated with:

• Neurodegenerative diseases (81% of cases), especially Lewy body disease 5
• Psychiatric disorders like schizophrenia and schizoaffective disorder
• Cerebrovascular events
• Substance abuse (particularly methamphetamine)

Age of onset differs significantly between neurodegenerative (average 72 years) and non-neurodegenerative causes (average 51 years) 5.

Neuroanatomical Basis

Recent research indicates Capgras syndrome results from disruptions in specific brain connectivity patterns:

• Lesions functionally connected to the left retrosplenial cortex (involved in familiarity perception)
• Lesions functionally connected to the right frontal cortex (involved in belief evaluation/expectation violation) 6

This explains how a single lesion can cause this complex syndrome without requiring multiple pathologies.

Diagnostic Approach

When evaluating a patient with suspected Capgras syndrome:

1. Obtain thorough collateral information from caregivers, as patients may minimize or deny their delusions 1
2. Assess for coexisting symptoms:
   • Visual hallucinations (present in 100% of Lewy body disease cases with Capgras) 5
   • Other cognitive impairments
   • Paranoid ideation
3. Consider neuroimaging:
   • CT cerebral is recommended as the initial study when intracranial pathology is suspected 1
   • Look for factors associated with abnormal findings: low Glasgow Coma Scale, lateralizing signs, elevated systolic blood pressure, low body temperature

Treatment Algorithm

First-Line Pharmacological Management:

1. Atypical Antipsychotics:

   • Risperidone: Start at 0.25mg/day, effective dose approximately 1mg/day, maximum 2mg/day 1
   • Olanzapine: Start at 2.5mg/day, maximum 10mg/day 1

2. Typical Antipsychotics:

   • Pimozide: Shown to be effective in case reports when other antipsychotics fail, dosing up to 8mg/day 2
   • Haloperidol: Start at 0.5-1mg orally at night, maximum 5mg/day 1

Non-Pharmacological Interventions:

• Establish predictable routines and explain procedures in simple language
• Use visual reminders and reduce environmental stimulation
• Employ repetition, reassurance, and redirection techniques
• Provide caregiver education about the condition
• Address any reversible causes of agitation before initiating treatment 1

Monitoring and Follow-up

• Regular medical evaluation at least every 6 months
• Monitor for improvement in delusions and other symptoms
• Watch for medication side effects:
  • Extrapyramidal symptoms (elderly patients are more susceptible)
  • Hyperprolactinemia
  • Weight gain
  • Somnolence
  • Cardiovascular effects (hypotension, bradycardia)
  • Falls

Special Considerations

• In Lewy body disease-associated Capgras, treatment should address both the delusions and visual hallucinations
• For younger patients with non-neurodegenerative causes, addressing underlying psychiatric conditions or substance use is crucial
• Implement fall prevention strategies, especially in elderly patients
• Develop individualized safety plans including personal supports and environmental modifications 1