Clock-Drawing Tasks as Predictive Measurements for Disease Classification Among Patients With Parkinson's Disease and Essential Tremor.

Background Nonmotor cognitive symptoms are widely being recognized in both Parkinson's Disease (PD) and Essential Tremor (ET), the two most common movement disorders. Clock-drawing (CD) test seems to be impaired early in the process of cognitive (executive) decline in PD. However, the optimal measures for detecting cognitive changes in ET patients have not been established. Examining whether the CD test is a quick test could identify frontal and visuospatial deficits in patients with Parkinson's disease (PD) and essential tremor (ET). Methods Visuospatial performance was assessed in 58 consecutive patients with ET and 75 with PD and 22 healthy controls (HC) who visited two neurological clinics of Athens in Greece. The CD and copy (CC) items of the PD-Cognitive Rating Scale were used as a test of visuospatial function. Results Both CD and CC scores were lower for ET compared to PD patients and HC (p=<0.001 for both comparisons). A binomial logistic regression showed that both CD and CC items predict if participants had ET or PD with high sensitivity 94.7% and specificity 87.9% and an area under the curve (AUC) 0.980 (95% confidence interval, 0.962-0.997). The model explained 86.1% (Nagelkerke R2) of the variance in the disease variable (ET/PD) and correctly classified 91.7% of the cases. Conclusion Patients with ET have more visuospatial deficits compared to PD and HC. CD task may be an easy, useful tool to track cognitive changes in nondemented patients with ET in clinical practice.