Objective: The aim of the study was to investigate differences in the progression of cognitive decline and cortical thinning evolution in Parkinson’s disease (PD) patients compared to healthy controls (HC).

Background: Although PD is a degenerative illness, changes over time in cognition are mild. Longitudinal studies have reported impairment in speed of processing, memory and verbal fluency. Cortical changes related to cognitive decline have been poorly investigated.

Methods: Forty-four PD patients and 22 HC underwent neuropsychological and magnetic resonance imaging assessment (scan interval μ=45.7 months). Repeated measures ANOVA were performed from adjusted z-scores. Patients were classified as having mild cognitive impairment (MCI) according to recent diagnostic criteria. FreeSurfer software was used for cortical thickness analyzes and results were corrected for multiple comparisons using pre-cached cluster-wise Monte Carlo simulation with 10,000 iterations. Reported cortical regions reached corrected significance level of p < 0.05.

Results: There were significant interactions group per time in Trail Making Test Part A (F=4.533; p=.037), Symbol Digit Modalities Test (F=8.313; p=.005), delayed recognition from Rey’s Auditory-Verbal Learning Test (F=5.158; p=.027) and Stroop Color (F=5.928; p=.018). Over 4 years, 20 (45.5%) patients had PD-MCI from which 11 (39.9%) were cognitively preserved at baseline and 2 (4.5%) PD-MCI patients converted to PD dementia. Comparison of whole brain cortical thickness maps showed that both groups had progressive significant cortical thinning in several regions of the posterior cortex. Significant cortical thinning in PD patients was found, specifically in left isthmus posterior cingulate and right inferior parietal. ln controls, changes over time were seen in the left lingual gyrus and insula, right caudal middle frontal and lateral occipital regions. However, no significant interaction group per time effects was seen between controls and patients. 

Conclusions: PD patients had significant decline of memory and processing speed and an increased rate of MCIs over time. According the cortical thickness measures, in our 4-year study there are evidences of progressive atrophy, but this atrophy was similar for patients and controls.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/cognitive-changes-and-cortical-thinning-evolution-of-parkinsons-disease-patients-4-year-follow-up/