Mild cognitive impairment in Parkinson’s disease: the Parkinson’s disease cognitive study (PACOS)

There is controversy regarding the definition and characteristics of mild cognitive impairment in Parkinson's disease. The Movement Disorder Society commissioned a Task Force to critically evaluate the literature and determine the frequency and characteristics of Parkinson's disease-mild cognitive impairment and its association with dementia. A comprehensive PubMed literature review was conducted using systematic inclusion and exclusion criteria. A mean of 26.7% (range, 18.9%-38.2%) of nondemented patients with Parkinson's disease have mild cognitive impairment. The frequency of Parkinson's disease-mild cognitive impairment increases with age, disease duration, and disease severity. Impairments occur in a range of cognitive domains, but single domain impairment is more common than multiple domain impairment, and within single domain impairment, nonamnestic is more common than amnestic impairment. A high proportion of patients with Parkinson's disease-mild cognitive impairment progress to dementia in a relatively short period of time. The primary conclusions of the Task Force are that: (1) Parkinson's disease-mild cognitive impairment is common, (2) there is significant heterogeneity within Parkinson's disease-mild cognitive impairment in the number and types of cognitive domain impairments, (3) Parkinson's disease-mild cognitive impairment appears to place patients at risk of progressing to dementia, and (4) formal diagnostic criteria for Parkinson's disease-mild cognitive impairment are needed. Copyright © 2011 Movement Disorder Society.

This study aimed at investigating the clinical usefulness of the Mental Deterioration Battery (MDB) in the neuropsychological diagnosis and characterization of the dementia syndrome. In this paper, we report: (a) normative data for various test scores derived from the analysis of performance of 340 normal subjects living in urban areas; (b) an evaluation of the reliability of the single tests and of the battery as a whole in differentiating normal subjects from patients affected by cognitive deterioration derived from the analysis of performance of 130 normal subjects living in rural areas and 134 patients affected by probable Alzheimer’s dementia; (c) a cluster analysis of performances of the 340 normal subjects in the standardization group to evaluate possible criteria of homogeneity according to which the various MDB scores tend to aggregate; (d) an analysis of performance profiles of 183 patients with right monohemispheric focal lesions, 159 patients with left unilateral lesions with aphasia and 131 left-lesioned nonaphasic patients to evaluate the specificity of the single tests of the battery in documenting a selective impairment of one of the two cerebral hemispheres. Results confirm the reliability of the MBD in discriminating between normal and demented patients and provide indications for use of the battery in differentiating qualitative patterns of cognitive impairment.

To describe the frequency of mild cognitive impairment (MCI) in Parkinson disease (PD) in a cohort of newly diagnosed incident PD cases and the associations with a panel of biomarkers. Between June 2009 and December 2011, 219 subjects with PD and 99 age-matched controls participated in clinical and neuropsychological assessments as part of a longitudinal observational study. Consenting individuals underwent structural MRI, lumbar puncture, and genotyping for common variants of COMT, MAPT, SNCA, BuChE, EGF, and APOE. PD-MCI was defined with reference to the new Movement Disorder Society criteria. The frequency of PD-MCI was 42.5% using level 2 criteria at 1.5 SDs below normative values. Memory impairment was the most common domain affected, with 15.1% impaired at 1.5 SDs. Depression scores were significantly higher in those with PD-MCI than the cognitively normal PD group. A significant correlation was found between visual Pattern Recognition Memory and cerebrospinal β-amyloid 1-42 levels (β standardized coefficient = 0.350; p = 0.008) after controlling for age and education in a linear regression model, with lower β-amyloid 1-42 and 1-40 levels observed in those with PD-MCI. Voxel-based morphometry did not reveal any areas of significant gray matter loss in participants with PD-MCI compared with controls, and no specific genotype was associated with PD-MCI at the 1.5-SD threshold. In a large cohort of newly diagnosed PD participants, PD-MCI is common and significantly correlates with lower cerebrospinal β-amyloid 1-42 and 1-40 levels. Future longitudinal studies should enable us to determine those measures predictive of cognitive decline.