Utility of the pareidolia test in mild cognitive impairment with Lewy bodies and Alzheimer's disease

Differentiating Prodromal Dementia with Lewy Bodies from Prodromal Alzheimer's Disease: A Pragmatic Review for Clinicians

This pragmatic review synthesises the current understanding of prodromal dementia with Lewy bodies (pDLB) and prodromal Alzheimer's disease (pAD), including clinical presentations, neuropsychological profiles, neuropsychiatric symptoms, biomarkers, and indications for disease management. The core clinical features of dementia with Lewy bodies (DLB)-parkinsonism, complex visual hallucinations, cognitive fluctuations, and REM sleep behaviour disorder are common prodromal symptoms. Supportive clinical features of pDLB include severe neuroleptic sensitivity, as well as autonomic and neuropsychiatric symptoms. The neuropsychological profile in mild cognitive impairment attributable to Lewy body pathology (MCI-LB) tends to include impairment in visuospatial skills and executive functioning, distinguishing it from MCI due to AD, which typically presents with impairment in memory. pDLB may present with cognitive impairment, psychiatric symptoms, and/or recurrent episodes of delirium, indicating that it is not necessarily synonymous with MCI-LB. Imaging, fluid and other biomarkers may play a crucial role in differentiating pDLB from pAD. The current MCI-LB criteria recognise low dopamine transporter uptake using positron emission tomography or single photon emission computed tomography (SPECT), loss of REM atonia on polysomnography, and sympathetic cardiac denervation using meta-iodobenzylguanidine SPECT as indicative biomarkers with slowing of dominant frequency on EEG among others as supportive biomarkers. This review also highlights the emergence of fluid and skin-based biomarkers. There is little research evidence for the treatment of pDLB, but pharmacological and non-pharmacological treatments for DLB may be discussed with patients. Non-pharmacological interventions such as diet, exercise, and cognitive stimulation may provide benefit, while evaluation and management of contributing factors like medications and sleep disturbances are vital. There is a need to expand research across diverse patient populations to address existing disparities in clinical trial participation. In conclusion, an early and accurate diagnosis of pDLB or pAD presents an opportunity for tailored interventions, improved healthcare outcomes, and enhanced quality of life for patients and care partners.

Pareidolias are a function of visuoperceptual impairment

Pareidolias, or the misperception of ambiguous stimuli as meaningful objects, are complex visual illusions thought to be phenomenologically similar to Visual Hallucination (VH). VH are a major predictor of dementia in Parkinson's Disease (PD) and are included as a core clinical feature in Dementia with Lewy Bodies (DLB). A newly developed Noise Pareidolia Test (NPT) was proposed as a possible surrogate marker for VH in DLB patients as increased pareidolic responses correlated with informant-corroborated accounts of VH. This association could, however, be mediated by visuoperceptual impairment. To understand the drivers of performance on the NPT, we contrasted performances in patient groups that varied both in terms of visuoperceptual ability and rates of VH. N = 43 patients were studied of whom n = 13 had DLB or PD with Dementia (PDD); n = 13 had PD; n = 12 had typical, memory-onset Alzheimer's Disease (tAD); and n = 5 had Posterior Cortical Atrophy (PCA) due to Alzheimer's disease. All patient groups reported pareidolias. Within the Lewy body disorders (PD, DLB, PDD), there was no significant difference in pareidolic response rates between hallucinating and non-hallucinating patients. Visuoperceptual deficits and pareidolic responses were most frequent in the PCA group-none of whom reported VH. Regression analyses in the entire patient cohort indicated that pareidolias were strongly predicted by visuoperceptual impairment but not by the presence of VH. These findings suggest that pareidolias reflect the underlying visuoperceptual impairment of Lewy body disorders, rather than being a direct marker for VH.