The delusional misidentification syndromes in patients with and without evidence of organic cerebral disorder: a structured review of case reports.

Two series, each of 50 cases of delusional misidentification reported in the literature, were analyzed in order to study the interaction between organic and functional mental processes. The details of the time course of the development of the delusional misidentification and related mental symptoms, the phenomenology, and evidence of cognitive impairment and/or cerebral damage were recorded. The first series of cases included delusional misidentification either of place, and/or of persons; the second series was limited to cases, published since 1977, with delusional misidentification of person, who had had an electroencephalogram (EEG) and/or computerised tomographic (CT) brain scan. Paranoid delusions, preceding the onset of the delusional misidentifications, were more common in cases without evidence of organic cerebral disorder. In the second series there was good evidence of an inverse relationship between the presence of paranoid delusions preceding the delusional misidentification, and the intensity of organic cerebral disorder; (1) no evidence clinically or on investigation, (2) evident only on investigation, or (3) evident clinically. In the first series delusional misidentification of place was more common in cases with evidence of organic brain disorder, whereas delusional misidentification of person was more common with functional mental disorder. Nevertheless the delusional misidentification was equally likely to involve objects of personal significance whether or not there was evidence of organic cerebral disorder. Paramnesic misidentifications were associated with both memory impairment and disorientation for time.