The Pattern of Cognitive Impairment Associated with the Motor Subtype in Parkinson's Disease

ABSTRACT

BACKGROUND: Previous studies have found over-representation of a postural instability and gait difficulty(PIGD) motor subtype in Parkinsons disease with dementia(PD-D). METHODS: One hundred twenty patients with Parkinson's disease(PD) were included in this study. All patients were evaluated by the Unified Parkinson's Disease Rating Scale(UPDRS) and neuropsychological tests. On the basis of the criteria for dementia(DSM-IV) and the results of the neuropsychological assessments, the patients were divided into the following three groups (1) non-demented(PD-ND), (2) mild cognitive impairment(PD-MCI), and (3) dementia (PD-D). In addition, patients were also grouped into the following two phenotypes based on the UPDRS components (1) tremor and (2) postural instability gait difficulty(PIGD)-predominant. We also analyzed the clinical characteristics and subtypes of the disease. In addition, the relationship between the cognitive impairments and the parkinsonian motor handicaps was evaluated. RESULTS: There was a significant relationship between cognitive impairment and the motor subtypes. The PIGD group had a higher prevalence of PD-D than the other group. In addition, there were significant correlations between the general cognitive functions and motor handicaps, especially those with axial symptoms. Multiple logistic regression analysis showed that the motor subtype was independently associated with the cognitive decline in PD. CONCLUSION: These findings support that cognitive decline in patients with PD is associated with a specific motor subtype. This association might be explained by the involvement of non-dopaminergic pathways. These results have implications for the clinical management of PD with regard to the motor symptoms and cognition.