Objective: We used a digitizing tablet during PCT as a potential tool for assessing early cognitive deficits in PD yet without major cognitive impairment.  We also aimed to uncover neural correlates of identified parameter(s) using whole brain MRI.

Background: Impaired copy of intersecting pentagons from MMSE (Pentagon Copy Test, PCT) has been shown to predict dementia in PD.

Method: We enrolled 27 PD patients without major cognitive impairment (median age 67.0, median disease duration 4.0.) and 25 age-matched healthy controls (HC) (median age 67.1). During parametrisation of drawing, we focused on the commonly used features and compared both groups using the Mann-Whitney U test. We further focused on parameters with significant correlation with cognitive domains’ z-scores. Selected parameters were used as covariates in the whole brain voxel-wise analysis using 3T MRI and voxel-based morphometry.

Results: PD patients differed from HC only in attention domain (p<0.0001). Regarding the drawing parameters, groups differed in Shannon entropy (horizontal in-air, p=0.003) which quantifies uncertainty of movement above a paper when performing a transition between two strokes (higher in PD than in HC). In PD we found a significant correlation between attention z-scores and median of Shannon entropy (horizontal in-air; R=-0.55, p=0.006, and vertical in-air; R=-0.56, p=0.004). MRI results revealed an association between median of Shannon entropy (horizontal in-air) and gray matter volume in the right superior parietal lobe (SPL) (p<0.05,FWE threshold p<0.001).

Conclusion: Using a digitizing tablet during PCT we identified a novel entropy-based parameter that differed between HC and PD groups and correlated with attention in PD. The parameter is associated with the right SPL gray matter variability.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/shannon-entropy-a-novel-tool-for-assessing-pentagon-drawing-in-parkinsons-disease/