Reduplicative paramnesia after a right frontal lesion.

Objective: To report a case of reduplicative paramnesia after a focal lesion localized in the right frontal subcortical region.

Background: It is suggested that a right frontal subcortical lesion alone may be sufficient to cause cognitive disturbance that can develop into reduplicative paramnesia. Clinical data have been scarce.

Method: We describe the clinical, neuropsychological, and neuroradiologic findings of a 69-year-old man with reduplicative paramnesia after a right frontal subcortical lesion.

Results: Observation and neuropsychological study showed visuospatial impairment, visual-dominant memory disturbance, anosognosia for cognitive disturbance, and mild frontal dysfunction with paranoid personality. Diffusion-weighted magnetic resonance imaging study showed a lesion localized in the right inferior posterior frontal subcortical area, and we could define 5 neural pathways involved with the lesion. We supposed that 4 of these were potentially related to reduplicative paramnesia: the medial inferior component of the superior longitudinal fasciculus and the fronto-occipital fasciculus, which are related to visuospatial processing; the anterior thalamic radiation, which is concerned with memory processes; and the uncinate fasciculus, which may be related to abnormal feelings of hyperfamiliarity.

Conclusions: A localized lesion in the right inferior posterior frontal subcortical area can cause cognitive dysfunction that may develop into reduplicative paramnesia. Paranoid personality and the change of the patient's hospital room might have triggered the reduplicative delusion in this case.