Differential Diagnosis of Primary and Secondary Capgras Delusions

Abstract

Review of the recent literature on Capgras syndrome reveals primary and secondary subtypes of the disorder having distinctly different neurodiagnostic findings, clinical presentations, and response to psychotropic medications. Primary cases tended to have negative neurodiagnostic work-ups, positive psychiatric histories (usually of paranoid schizophrenia), and gradual onset before age 40. Paranoia and violence were common in these primary cases, but neuroleptic response was good. In contrast, the secondary Capgras cases had positive neurodiagnostic findings (usually indicating right frontotemporal dysfunction), negative psychiatric histories, and sudden onset after age 40. There was a relative absence of paranoia and violence and more variable response to neuroleptics in the secondary cases. Two cases epitomizing the primary and secondary types are described, and a neuropsychological model for the disorder is presented.