Distortion errors characterise visuo-constructive performance in Huntington's disease

Objective: Visuospatial deficits have been extensively studied in Huntington's disease (HD), particularly in relation to visuomotor integration, with less emphasis on visuo-constructive abilities. Quantitative analyses have demonstrated that individuals with HD perform worse than healthy controls (HC) but similarly to people with Alzheimer's disease (AD). The aim of the present study was to conduct a qualitative investigation of visuo-constructive abilities in both HD and AD. By employing both simple and complex tasks, we hypothesized that a qualitative analysis of performance would reveal a distinct pattern of errors specific to HD. Methods: Participants for this study were identified retrospectively. The sample included 41 individuals with HD, 25 with AD, and 35 HC. All participants underwent a neuropsychological battery, which included the Constructional Apraxia Test (CAT) and the Rey-Osterrieth Complex Figure (ROCF) test. Results: Our results showed no significant quantitative difference in visuo-constructive performance between the two patient groups. However, distinct qualitative patterns of drawing errors emerged. Simplifications were more frequent in the AD group, while distortions were distinctive errors in the HD group. These qualitative error patterns were consistent across both the CAT and ROCF. Conclusion: Our study emphasises the value of qualitative analysis in interpreting visuo-constructive performance, shifting the focus from "how much" a participant achieves to "how" they perform a neuropsychological task. This qualitative approach is useful to capture the complexity and variability of individual performance, providing deeper insight into the cognitive processes affected by different neurological conditions.