Anatomical and psychological mechanism of reduplicative misidentification syndromes

Reduplicative misidentifications syndromes (RMS) are rare memory disorders characterized by the subjective conviction that a place, person or event is duplicated. Even if RMS often follow a right frontal lesion, several studies have stressed the importance of bilateral hemispheric pathology. Moreover, from a psychological perspective, there is uncertainty if this symptom should be considered just as a kind of confabulation or if it should be associated with personal psychosocial and behavioral aspects. We report a patient who developed normal pressure hydrocephalus and RMS one year after a post-traumatic right frontal lesion. At the first neuropsychological evaluation, we found mild impairment of all functions, associated with the presence of reduplicative paramnesia. After the ventricle-peritoneal shunt intervention, we observed a progressive improvement of all functions but the frontal ones. The memory deficit became less specific and the RMS disappeared. We therefore postulate that a focal right frontal lesion is not sufficient to cause RMS per se. Our clinical report suggests that paramnesic events held on reasonable ground, not being just a kind of confabulation.