Misidentification—reduplication and the right hemisphere

Misidentification syndromes, such as Capgras syndrome (CS) and reduplication syndrome (RS), have been associated with right hemisphere dysfunction. We report a 77-year-old woman who misidentified her mirror-image as another person identical to herself. Examination revealed a left homonymous hemianopsia. Magnetic resonance imaging (MRI) showed right temporoparietal atrophy. Published cases of CS (n = 26) and RS (n = 96) were reviewed in which brain dysfunction was implicated. In CS, there was a trend toward greater occurrence of right-versus left-sided abnormality (x² = 3.6. p = 0.06); in RS, there was a significantly greater occurrence of right-sided cases (x² = 23.4, p = 0.0000). This suggests that CS and RS are associated with right hemisphere dysfunction. Furthermore, cortical stimulation studies have shown that right temporal lobe stimulation may elicit experiences of familiarity-unfamiliarity. We conclude that the right hemisphere, and particularly, the right temporal lobe, may be dominant for a sense of familiarity with environmental stimuli.