Morphometric magnetic resonance imaging cortico-subcortical features in Parkinson's disease with mild cognitive impairment

Background and purpose Parkinson's disease (PD) patients with cognitive impairment undergo progressive atrophy of several cortical and subcortical areas. The aim was to study the magnetic resonance imaging (MRI) morphometric features of PD patients with mild cognitive impairment (MCI). Methods Patients from the Parkinson's Disease Cognitive Impairment Study (PACOS) cohort with an available structural volumetric brain MRI and morphometric measurements of the midbrain and pons areas, middle cerebellar peduncle, superior cerebellar peduncle width and midbrain anteroposterior diameter (A-Pdiam) were included. MCI was diagnosed according to the Movement Disorder Society level II criteria. Additionally, cortical thickness analysis was performed and correlated with morphometric brainstem measurements. Results Morphometric measurements were available for 168 subjects, of whom 67 (39.9%) were diagnosed with PD-MCI. The mean age (+/- standard deviation) of the sample was 64.2 +/- 9.8. Amongst patients, 84 (50%) were men with a disease duration of 5.2 +/- 5.4 years and a Unified Parkinson's Disease Rating Scale-Motor Examination score of 32.1 +/- 12.9. In the univariate and multivariate analysis, after adjusting for age, sex, years of schooling and disease duration, MCI was associated with midbrain area (odds ratio 0.98; 95% confidence interval 0.96-0.99; p = 0.048) and A-Pdiam (odds ratio 0.63; 95% confidence interval 0.46-0.86; p = 0.005). Furthermore, 121 PD patients underwent cortical thickness analysis, which showed the presence of cortical thinning in lateral orbitofrontal regions of patients with PD-MCI. No correlation was found between cortical thickness and brainstem morphometric measurements. Conclusions A mild midbrain atrophy and the presence of frontal cortical thickness reduction might be considered a structural MRI feature of PD patients with MCI.