misidentification syndrome

   Also known as delusional misidentification syndrome. Both terms are used as an umbrella term for a diverse group of conditions in which the affected individual consistently misidentifies a person, object, place, or event. The symptoms and syndromes included in the misiden-tification syndrome tend to vary somewhat in different classifications. Four subtypes are commonly distinguished, i.e. the * phantom boarder syndrome (which involves the imagined or hallucinated presence of one or more persons in the home of the affected individual); *mirrored self-misidentification (i.e. the inability to recognize oneself in a reflecting surface); misidentification of other persons (as in prosopagnosia, *intermetamorphosis syndrome, * Capgras' syndrome, *Frégoli's phenomenon, and the * syndrome of subjective doubles); and the *TV sign (in which the affected individual imagines the events on television as occurring in external, three-dimensional space). Other syndromes included under the heading misidentification syndrome are the * magazine sign (in which people or objects in magazines are treated as if they were present in the affected individual's home), the * picture sign (in which persons depicted in portraits are treated as present in the individual's home), the syndrome of subjective doubles (in which the affected individual believes that he or she has a *doppelgänger or * double living a separate life), clonal pluralization of the self (in which the affected individual believes that multiple copies of himself or herself exist, which are identical both physically and psychologically), reduplicative paramnesia (involving the conviction that a familiar person, place, or object has been duplicated), and the syndrome ofdelusional companions (i.e. the belief that toys or other objects are sentient beings). Misidentification syndromes are traditionally associated with psychiatric disorders such as *psychotic and affective disorders, but also with organic brain conditions such as viral encephalitis, Alzheimer's disease, and other types of dementia. Although they may occur in the absence of any demonstrable pathology ofthe brain, it has long been suspected that disorders belonging to the misidentifica-tion syndrome must have discrete neuroanatom-ical correlates, tentatively located in the right hemisphere. Evidence emerging from neuroimag-ing studies indicates that various discrete brain regions do indeed play a key role in their mediation. These candidate regions include the right fusiform gyrus (believed to play a major role in the identification of faces), the parahippocampal place area (believed to play a similar role in the identification of places), and the anterior middle and inferior temporal gyri (associated with long-term memory and mechanisms for the retrieval of memorized information). In some classifications, conditions characterized by misidentifica-tion as well as reduplication are referred to as delusional reduplication syndromes. It is open to debate whether these two groups of conditions are worthy of the predicate 'syndrome'. They are more like umbrella terms for a group of separate symptom clusters which have as their common denominator the fact that they lie on a continuum of anomalies of familiarity. It is equally open to debate whether these separate syndromes are primarily illusory or delusional in nature. In psychiatric classifications they tend to be relegated to the group of monothematic delusions. And yet in some instances, hallucinatory or at least illusory perception would seem to play a role. As early as 1866, the German psychiatrist Karl Ludwig Kahlbaum (1828-1899) described various misidentification syndromes, which he designated as Sinnesdelirien (i.e. * delirium of the senses) and which he relegated to the class of * illusions. Conversely, the German psychiatrist and neurologist Arnold Pick (1851-1924), whose concept of reduplicative paramnesia signalled a growing interest in cases of misidentification around the fin de siècle, regarded them as disorders ofmemory.

   References

   Burns, A. (1997). Misidentifications. International Psychogeriatrics, 8, 393-397.

   Feinberg, T.E., Deluca, J., Giacino, J.T., Roane, D.M., Solms, M. (2005). Right-hemisphere pathology and the self: Delusional misidentification and reduplication. In: The lost self. Pathologies ofthe brain and identity. Edited by Feinberg, T.E., Keenan, J.P. Oxford: Oxford University Press.

   Förstl, H., Almeida, O.P., Owen, A.M., Burns, A., Howard, R. (1991). Psychiatric, neurological and medical aspects of misidentification syndromes: A review of 260 cases. Psychological Medicine, 21, 905-910.

   Hudson, A.J., Grace, G.M. (2000). Misidentification syndromes related to face specific area in the fusiform gyrus. Journal of Neurology, Neurosurgery and Psychiatry, 69, 645-648.

   Pick, A. (1903). Clinical studies. Brain, 26, 242-267.