Noise Pareidolia Test in Parkinson's Disease and Atypical Parkinsonian Syndromes: A Retrospective Study

Abstract

Introduction: Pareidolias, or visual misperceptions, are a non-motor symptom of Parkinson's disease (PD) with unclear pathophysiology. The noise pareidolia test (NPT) is a tool for screening pareidolias. The usefulness of the NPT in differentiating PD from atypical parkinsonian syndromes (APS) is also unknown.

Methods: We retrospectively investigated 74 patients with PD and 18 patients with APS who took the NPT. Correlations between the number of pareidolic responses, gray matter volume, and cerebral blood flow were also examined in the patients with PD.

Results: The median number of pareidolic responses in patients with PD and patients with APS was 0 (interquartile range (IQR): 0-3) and 0 (IQR: 0-1), respectively, and tended to be higher in patients with PD than in those with APS (p = 0.077). It was significantly higher in patients with PD who had hallucinations (2; IQR: 0-9) (p = 0.016). The area under the receiver operating characteristic curve for the number of pareidolic responses in the NPT was 0.62 when used to differentiate PD and APS, and the optimal cutoff number of pareidolic responses was 2/3. Sensitivity and specificity were 25.7% and 100%, respectively. In the PD group, the number of pareidolic responses was correlated with age (r = 0.27; p = 0.021) and the Frontal Assessment Battery (FAB) score (r = -0.34; p = 0.0099). Magnetic resonance imaging showed no significant correlation between the number of pareidolic responses and the volume of focal gray matter. On cerebral hypoperfusion mapping, the left parietal lobe had a significant correlation with the number of pareidolic responses (r = 0.35; p = 0.027).

Conclusion: The number of pareidolic responses in NPT was suggested to be useful as a red flag to rule out APS in differentiating PD from APS. In PD without dementia, the number of pareidolic responses was associated with reduced blood flow in the left parietal lobe.

Keywords: atypical parkinsonian syndrome; noise pareidolia test; pareidolia; parkinson’s disease; visual hallucination; visual misperception.

Figure 1. Number of pareidolic responses on the noise pareidolia test in patients with PD and APS

The number of pareidolic responses tended to be higher (p = 0.077) and had a larger variance in PD than in APS. PD: Parkinson’s disease; APS: atypical parkinsonian syndrome

Figure 2. Correlation of age and FAB score with pareidolia in patients with PD

The pareidolic responses correlated with (a) age (r = 0.27; p = 0.021) and (b) FAB score (r = −0.34; p = 0.0099). FAB: Frontal Assessment Battery; PD: Parkinson’s disease

Figure 3. Correlation between pareidolia and left parietal lobe cerebral blood flow in patients with PD

a: Brain surface image on vbSEE; the left parietal lobe is highlighted according to Talairach’s classification; b: The scatter plots show the extent of decrease in cerebral blood flow in the left parietal lobe and the number of pareidolic responses. PD: Parkinson’s disease; vbSEE: voxel-based stereotactic extraction estimation; L: left