Objective: To investigate the relationship between impairments of the cardinal motor impairments and color discrimination deficits in Parkinson’s disease (PD).

Background: Previous studies have shown that impaired color discrimination functions reflect cognitive deficits in PD, in particular executive and visuospatial deficits. Such cognitive deficits may also contribute to postural instability gait difficulties (PIGD) motor features in PD.

Methods: PD patients, n=55 (F14; 67.2±7.3 (54-86) years old; 7.4±5.3 (0.5-20) years motor disease duration) tested color discrimination using the Farnsworth-Munsell 100 Hue Test (FMT). MDS-UPDRS motor and gait assessment was performed in the dopaminergic “off” state. Subscores for the cardinal motor symptoms (tremor, rigidity, PIGD and distal bradykinesia) were calculated. 8.5-meter walking time and timed up and go test (TUG) were also assessed.

Results: The mean FMT total error score was 101.2±88.8 (range 4-428). There was a significant inverse correlation between performance on the FMT and MOCA cognitive scores (R=-0.39, P=0.003). There was also a significant correlation between the FMT and total MDS-UPDRS motor scores (R=0.31, P=0.02). Stepwise regression analysis using the FMT as the outcome parameter and the four rank-normalized MDS-UPDRS motor sub-scores showed a significant model with PIGD features (F=5.73, P=0.02) as the only significant motor parameter in the model. Multiple regression analysis using the rank-normalized PIGD scores as the outcome parameter and FMT, age and duration of motor disease as regressors yielded a significant total model (F=4.17, P=0.01) with significant effects for FMT scores (F=5.14, P=0.028), duration (F=4.34, P=0.05) but not age (F=1.54, ns). There were also significant correlations between performance on the FMT and the rank-normalized timed gait (R=0.37, P=0.0065) and TUG tests (R=0.47, P=0.0003). Multiple regression analysis using the rank-normalized TUG as outcome parameter showed significant predictor effects for FMT (F=14.35, P=0.0004), age (F=5.43, P=0.023) but not for duration of disease (F=1.82, ns; total model F=8.04, P=0.0002).

Conclusions: Impaired color discrimination selectively associates with PIGD motor features in PD. Findings may reflect a shared pathophysiology between impaired color discrimination, cognitive impairment and axial motor symptoms in PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/impaired-color-discrimination-selectively-associates-with-postural-instability-and-gait-difficulties-in-parkinsons-disease/