Objective: Measuring experimentally-induced presence hallucinations in patients with Parkinson’s disease phantom boarder phenomena.

Background: Phantom boarder syndrome (PB) is described as the sensation that someone uninvited, or stranger, enters or lives in the patient’s home despite evidence to the contrary. It is mostly reported by patients with advanced neurodegenerative disorders such as Alzheimer’s disease, dementia with Lewy body or Parkinson’s disease (PD) dementia (Aarsland et al., 2001). Presence hallucination (PH) is the sensation that someone is nearby, behind or next to the patient (when nobody is actually there). Because PB and PH share several clinical aspects and because recent work had induced experimentally-controlled PH with a robotic system in PD patients (Bernasconi et al., 2021), we investigated if PD patients with PB (PD-PB) would show elevated sensitivity for robot-induced PH (riPH).

Method: We studied the sensitivity of 4 PD-PB patients in a sensorimotor stimulation paradigm, during which patients moved, with the hand, a robotic device placed in front of them. A second robot placed behind them reproduced their movements, delivering tactile feedback on their back with varying temporal delays (0-500ms, by step of 100ms). This task created riPH in PD patients (2). The sensitivity of the PD-PB patients to sensorimotor conflicts was compared with that of 2 other groups of PD patients (patients with PH but no PB: PD-PH; patients without PB nor PH: PD-nH). All patients were screened for dementia, and the phenomenology of PB and PH was assessed by a semi-structured clinical interview.

Results: The results showed that the intensity of riPH increased with increasing delay of asynchrony between the movement and the tactile feedback for all 3 groups (delay dependency). Importantly, post-hoc analysis revealed that both PD-PB and PD-PH had a higher delay sensitivity compared to PD-nH. There was no difference between PD-PB and PD-PH. None of the patients suffered from dementia, nor delusional misidentification.

Conclusion: We report data in PD patients with PB and found that they are more vulnerable to the experimental induction of PH than PD-nH and similarly vulnerable compared to PD-PH. These behavioral data suggest that PB and PH share important underlying brain mechanisms of perceptual nature involving sensorimotor signals and their integration.

References: 1. Aarsland D, Ballard C, Larsen JP, McKeith I. A comparative study of psychiatric symptoms in dementia with Lewy bodies and Parkinson’s disease with and without dementia. Int J Geriatr Psychiatry. 2001;16(5):528–36.
2. Bernasconi F, Blondiaux E, Potheegadoo J, Stripeikyte G, Pagonabarraga J, Bejr-Kasem H, et al. Robot-induced hallucinations in Parkinson’s disease depend on altered sensorimotor processing in fronto-temporal network. Sci Transl Med. 2021 Apr 28;13(591).

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MDS Abstracts - https://www.mdsabstracts.org/abstract/phantom-boarder-syndrome-associated-with-experimentally-induced-presence-hallucinations-in-parkinsons-disease/