To the Editor: Reduplicative paramnesia (RP) is characterized by a subjective certainty that a place has been duplicated;1 it is considered a type of delusional misidentification having a clear parallel with Capgras’ delusion, which involves reduplication of people.2 Reduplicative paramnesia most often occurs in patients with neurodegenerative disorders, stroke, head trauma, or psychiatric disorders.3–5 We describe four patients with RP and try to explain how RP helps us analyze the underlying causes of this delusional syndrome, related to implicit and explicit memory circuits.
In 1905, Pick6 described a hospitalized woman in Prague who was convinced of another identical hospital existing in the neighboring city, with identical rooms and doctors. Pick named the disorder RP because he saw the disorder as a reduplication of memory, and, since this first case, even if several patients have been reported, RP is considered an infrequent disorder that allows neurologists to explore the fascinating mechanism of memory circuits.
The description of these four cases gave us the opportunity to underline the heterogeneity of this disorder with regard to possible causes and type of manifestations.
Patient #1 had a temporal lobe lesion (meningioma); was never confused; and she could analyze her symptoms. Her neuropsychological examination and her daily autonomy did not reveal any memory damage.
Patient #2, with a frontotemporal stroke, was temporarily confused; he reduplicated his room in the hospital and was unaware of his disorder.
Patient #3 had been treated for depression for many years and manifested signs of RP some months before symptoms related to late-onset psychosis. He reduplicated his home, was not confused, and was initially aware of his unusual situation.
Patient #4 had chronic frontotemporal dysfunction from dementia. She reduplicated her home, initially sometimes and with partial awareness, then more constantly when the degenerative process was worsening.
Why does a patient reduplicate only temporarily their unfamiliar room in the hospital and others reduplicate a familiar place (their home)? Is there the same mechanism at work for these different cases? A confusional state is not always associated with RP, but, when patients with RP are confused, they reduplicate any place, even if is not a familiar place. As for other reduplicative syndromes, a theoretical dysfunction of implicit/emotional memory circuits is considered to be the underlying cause of RP, and many authors have underlined the importance of frontal or temporal lobe damage.7 Not all of these patients had abnormal functioning of episodic memory (see Patient #1), and this suggests that only an implicit memory disorder is necessary to RP manifestations.8,9
Recent tractography evidence confirms that visually specialized cortical areas are connected by two parallel pathways: 1) the ventrolateral parieto-frontal U-shaped fibers; and 2) the direct occipito-temporal pathway or inferior longitudinal fasciculus (ILF), connecting pre-striate cortex to medial temporal structures (the hippocampus, parahippocampal gyrus, and amygdala). It is possible that the direct occipito-temporal pathway relates to emotional visual memory.10 Furthermore, the superior longitudinal fasciculus (SLF; connecting the visual parietal lobe and frontal cortex) and the inferior fronto-occipital fasciculus (IFOF; connecting areas in the occipital lobe and ventral frontal lobe) are likely to relate to functions such as visual working memory and visual attention. “Hodological” disorders relates higher function and dysfunction to connections between different locations, and RP can be considered a type of hodological disorder for a disconnection of visual and affective or memory regions.11–13
Furthermore, implicit storage of information does not require attention,12 so a confused patient can encode implicit information about a place, but when he sees that place again, with his fluctuating mental state, he does not recollect that place (SLF or IFOF dysfunction?); it is an old place, unconsciously, and a new place, consciously, so there are two identical places. Patients with no confusional state associated, as Patient #1, who present with temporary visuolimbic damage or, maybe, occipito-temporal fasciculus, can show symptoms of reduplication, but they are able to stigmatize their symptoms and try to find a logical explanation.
In conclusion, RP can occur transiently or chronically in relation to different causes; specific visual memory circuits (maybe including ILF or SLF and IFOF) can be damaged, producing different forms of reduplication related to familiar or unfamiliar places; amnesic syndrome is not necessary to produce RP (see Table 1).
TABLE 1.Findings in Patients With Reduplicative Paramnesia
| Add to My POL
|TAB Neuropsychological Test Results||Patient #1||Patient #2||Patient #3||Patient #4|
|General mental status||MMSE||29/30||26/30||28/30||24/30|
|Digit span||Digit Span forward||5||—||5||5|
|Visuospatial attention||Corsi Blocks test||5||—||4||4|
|Attention||Trail-Making A – B||—||—||93 – 435||A: 301|
|Verbal fluency (FAS)||—||—||7||21|
|Memory||RAVLT immediate recall||—||—||20/75||28/75|
|RAVLT delayed recall||2/15||2/15|
|RAVLT multiple recognition||13/15||15/15|
|Rey Figure recall||—||—||8/36|
|Rey Figure Copy||—||—||31/36||—|
|BNT 20 figures||18/20||—||20/20||17/20|
In the future, it would be very interesting to study those cases with Diffusion Tensor Imaging (DTI) to demonstrate whether damage exists to specific tracts carrying reciprocal connections between the occipital lobe, the hippocampus, the amygdala, and the frontal lobe.