Correlation between motor and cognitive functions in the progressive course of Parkinson's disease

Abstract

Aim: Correlations between motor function and frontal-executive function in Par-kinson's disease (PD) have been examined previously, but correlations with other cognitive domains remain unknown. We examined the correlation between motor dysfunction and cognitive impairment with regard to their precise domains. Methods: Motor and cognitive functions were assessed in 61 patients. To assess motor function, the Unified Parkinson's Disease Rating Scale (UPDRS) was administered. The UPDRS score was assessed as general motor function with a sum of Parts II and III, and as subscores of individual motor symptoms (rigidity, tremor, akinesia and postural instability). To assess cognitive function, the Mon-treal Cognitive Assessment (MoCA) and the Frontal Assessment Battery (FAB) were administered. MoCA was assessed by a total score and subscores of six cognitive subdomains: visuospatial, executive, attention/concentration/working memory, language, memory and orientation. The correlation coefficients of both MoCA and FAB with patient background and motor symptoms were compared using Spearman's correlation coefficient. Results: General motor function and the subscore of postural instability showed significant negative correlations with MoCA, FAB, and the subdomains of visuo-spatial, executive and orientation skills. Tremor and rigidity showed no significant correlation with any cognitive assessment. Akinesia showed significant negative correlation with MoCA, and the subdomains of visuospatial and orientation skills. Conclusions: In patients with PD, specific motor and cognitive functions correlate, with particular regard to postural instability and visuospatial skills. The correla-tions suggest functional links between a number of cerebral cortices and subcorti-cal structures, and a common pathophysiology for motor and cognitive impairments in PD.