Although visual hallucinations are one of the core clinical features differentiating dementia with Lewy bodies from other dementias, clinicians rarely witness patients as they experience them ( McKeith et al., 1996, 2005).
It is difficult to determine whether false perceptions arise independently of real visual scenes or as a result of their distortion.ĭementia with Lewy bodies is arguably the most common cause of visual hallucinations in the elderly. However, it is inevitable that when patients are awake and have their eyes open, they see things. According to this definition, a visual hallucination is experienced when one sees something where nothing actually exists. ‘A perception without an object’ is the classic definition of a hallucination and has been in use since the end of the 19th century ( Ey, 1973). Arousal and attentional deficits mediated by abnormal cholinergic mechanisms and visuoperceptual dysfunctions are likely to contribute to the development of visual hallucinations and pareidolias in dementia with Lewy bodies.Īcetylcholine, dementia with Lewy bodies, visual hallucinations, visual illusions Introduction A sub-analysis of patients with dementia with Lewy bodies who were or were not treated with donepzil demonstrated that the numbers of pareidolias were correlated with visuoperceptual abilities in the former and with indices of hallucinations and delusional misidentifications in the latter. Pareidolias were observed in patients with dementia with Lewy bodies who had visual hallucinations as well as those who did not have visual hallucinations, suggesting that pareidolias do not reflect visual hallucinations themselves but may reflect susceptibility to visual hallucinations. Full-length figures and faces of people and animals accounted for >80% of the contents of pareidolias. A receiver operating characteristic analysis demonstrated that the number of pareidolias differentiated dementia with Lewy bodies from Alzheimer’s disease with a sensitivity of 100% and a specificity of 88%. Patients with dementia with Lewy bodies produced a much greater number of pareidolic illusions compared with those with Alzheimer’s disease or controls.
Thirty-four patients with dementia with Lewy bodies, 34 patients with Alzheimer’s disease and 26 healthy controls were given the Pareidolia test. In this study, we explored the clinical utility of a newly developed instrument for evoking pareidolic illusions, the Pareidolia test, in patients with dementia with Lewy bodies-one of the most common causes of visual hallucinations in the elderly.
Pareidolias, which are complex visual illusions involving ambiguous forms that are perceived as meaningful objects, are analogous to visual hallucinations and have the potential to be a surrogate indicator of visual hallucinations. Therefore, instruments to detect visual hallucinations directly from patients are needed. Patients rarely experience visual hallucinations while being observed by clinicians.
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