Interlocking pentagons task and visuospatial deficit in parkinsonian syndrome: a quantitative approach

Visuo-spatial impairment is a common feature in parkinsonian disorders and differentiating idiopathic Parkinson's disease (PD) from atypical parkinsonian syndromes (APS), i.e. progressive supranuclear palsy (PSP), multiple system atrophy (MSA), and corticobasal degeneration (CBD), remains a major clinical challenge. The Qualitative Scoring Pentagon Test (QSPT), derived from the MMSE pentagon-copying item, provides quantitative visuo-constructive assessment but has not been systematically evaluated as a differential marker in parkinsonism. Aim of the study was to assess the discriminative value of the QSPT total score and sub-items across parkinsonian syndromes, and to examine associations with neuropsychological tests, motor severity, and MRI morphometric indices.

Patients with PD and APS were enrolled and underwent clinical and neuropsychological evaluations including MMSE, Frontal Assessment Battery (FAB), Trail Making Test (TMT-A), and MDS-Unified Parkinson's Disease Rating Scale-Section III (MDS-UPDRS-III). A group of healthy controls (HC) were also enrolled performing MMSE. Pentagon drawings were scored quantitatively (QSPT). When available, MRI morphometric features were collected. Statistical analysis were performed to assess associations between QSPT, cognitive and clinical features, and to evaluate differences between patients and HC and across patients' groups.

One-hundred and forty patients (PD=91, PSP=23, MSA=17, CBD=9) and 92 HC were enrolled. QSPT differed significantly considering HC performances (12.7 ± 0.5) versus patients groups, and across groups (p<0.001), with PD scoring the highest (11.5 ± 2.1) and CBD the lowest score (7.7 ± 4.4). PD differed from PSP (p<0.001), CBD (p<0.001) and MSA (p=0.040). Rotation and number-of-angles sub-items were the most discriminating features. QSPT significantly correlated with MMSE, FAB, TMT-A, and MRPI (all p<0.01). Multivariate models demonstrated that QSPT was independently associated with APS (OR=0.620, 95%CI 0.469-0.820, p<0.001). A QSPT score ≤ 8 points discriminated PD from APS with an AUC of 0.764 and a specificity of 92.3%, and ≤ 11 points discriminated synucleinopathies from tauopathies with a higher AUC (0.804).

This study demonstrates that quantitative scoring of the MMSE pentagon-copying item could differentiate PD from APS. The presence of association between QSPT and MRI brainstem morphometry could also reflect a structural association, specifically identifying tauopathies. QSPT could be a simple and supportive clinical tool, embedded within the MMSE that could differentiates patients from HC and PD from APS.