1AP-HP, Groupe HospitalierHenri-Mondor, Service deneurologie, Cre´teil, France.
J Neurol Neurosurg Psychiatry. 2011 Nov;82(11):1219-24. doi: 10.1136/jnnp.2010.234799. Epub 2011 May 7.
A feeling of presence (FP), that is, the vivid sensation that somebody (distinct from oneself) is present nearby, is commonly reported by patients with Parkinson's disease (PD), but its phenomenology has not been described precisely. The objective of this study was to provide a detailed description of FP in PD and to discuss its possible mechanisms.
The authors studied 52 non-demented PD patients reporting FP in the preceding month (38 consecutive outpatients and 14 inpatients). FP characteristics were recorded with a structured questionnaire. The outpatients with FP were compared with 78 consecutive outpatients without FP.
About half the patients said they recognised the 'identity' of the presence. More than 75% of patients said the FP were not distressing, were short-lasting, were felt beside and/or behind the patient, and occurred while indoors; most patients checked for a real presence, but their insight was generally preserved. In 31% of cases, the patients had an unformed visual hallucination simultaneously with the FP. A higher daily levodopa-equivalent dose and the presence of visual illusions or hallucinations were independently associated with FP.
Although FP is not a sensory perception, projection of the sensation into the extrapersonal space, along with the frequent co-occurrence of elementary visual hallucinations and the strong association with visual hallucinations or illusions, supports its hallucinatory nature. FP may be viewed as a 'social' hallucination, involving an area or network specifically activated when a living being is present, independently of any perceptual clue.
存在感（FP）是指患者生动地感觉到有人（与自身不同）在附近存在，这在帕金森病（PD）患者中很常见，但FP 的现象学尚未得到准确描述。本研究旨在详细描述 PD 患者的 FP，并讨论其可能的机制。
作者研究了 52 名在过去一个月内报告存在 FP 的非痴呆 PD 患者（38 名连续门诊患者和 14 名住院患者）。使用结构化问卷记录 FP 特征。将存在 FP 的门诊患者与 78 名连续无 FP 的门诊患者进行比较。
约一半的患者表示他们识别出了存在的“身份”。超过 75%的患者表示 FP 并不令人痛苦，持续时间短，感觉在患者旁边和/或后面，发生在室内；大多数患者会检查是否真的存在，但他们的洞察力通常保持完好。在 31%的情况下，患者同时存在 FP 和未成形的视觉幻觉。较高的每日左旋多巴等效剂量和存在视觉错觉或幻觉与 FP 独立相关。
尽管 FP 不是一种感觉知觉，但将感觉投射到外在空间，加上经常同时出现的基本视觉幻觉，以及与视觉幻觉或错觉的强烈关联，支持其幻觉性质。FP 可以被视为一种“社交”幻觉，涉及到当有生物存在时特别激活的一个区域或网络，而与任何感知线索无关。
