Neuropsychological Characteristics of Mild Cognitive Impairment in Parkinson Disease and Subcortical Vascular Mild Cognitive Impairment

ABSTRACT

BACKGROUND: Patients with Parkinson's disease and mild cognitive impairment (PD-MCI) and patients with subcortical vascular mild cognitive impairment (svMCI) are known to have cognitive dysfunction. The aim of this study was to determine the cognitive characteristics that can be used to differentiate these two conditions. METHODS: Twenty-two PD-MCI and 22 svMCI patients seen in our neurodegenerative disease clinic, and 22 normal controls were recruited. These three groups were matched in terms of age, gender, and education level. Mild cognitive impairment was diagnosed according to the criteria of Petersen. svMCI should meet the criteria modified from those of Erkinjuntti. RESULTS: Analysis of covariance revealed that frontal executive dysfunction was prominent in both the PD-MCI and svMCI groups after adjusting for depression. The scores in word fluency and the Stroop test were lower in the svMCI group than in the PD-MCI group. Both groups exhibited decreased performance in verbal and visuospatial memory tests. The score in the verbal recognition test was lower in the PD-MCI group than in the svMCI group, which exhibited comparatively reduced visuospatial memory. The depression level was higher in the PD-MCI group than in the svMCI group, as assessed using the Geriatric Depression Scale. CONCLUSIONS: The impairment in frontal executive function was more severe in the svMCI group than in the PD-MCI group, which displayed severe impairment in verbal memory function. These differences in cognitive function may help to differentiate PD-MCI from svMCI, and to further the understanding of their pathophysiologies. PD-MCI patients also exhibited severe depressive mood, which raises the possibility of cognitive improvement through therapy.