Objective: To identify baseline structural brain differences between individuals with Parkinson’s disease (PD) who go on to develop mild cognitive impairment (PD-MCI) and those who remained cognitively stable (PD-NC stable) using voxel-based morphometry (VBM).

Background: PD has traditionally been characterized by motor symptoms. However, most people with PD will also experience cognitive deficits, which can be more disabling than motor symptoms [1]. The ability to detect changes in brain structure prior to observable changes in cognition may allow for the early identification of patients with PD who have the highest likelihood of developing PD-MCI which confers risk for dementia [2].

Method: Data was obtained from the Parkinson’s Progression Markers Initiative. The sample included newly diagnosed patients with PD who underwent a structural MRI and cognitive assessment at baseline, and a minimum of one annual cognitive follow-up. Participants were classified as PD-NC and PD-MCI at each timepoint using the Movement Disorder Society Task Force Level I criteria [3]. Participants were classified as PD-NC if they were impaired (< 1.5 SD below normative means) on fewer than two cognitive measures and as PD-MCI if they were impaired on at least two cognitive measures. Participants who remained PD-NC at all follow-ups were further classified as PD-NC stable and those who converted to PD-MCI at any follow-up as PD-MCI converters. Structural MRI analyses were conducted using the FSL-VBM pipeline. The analyses examined whether there were structural brain differences at baseline between PD-MCI converters and PD-NC stable groups. Given the small sample size, the PD-MCI converter group (n=9) was compared to two groups of PD-NC stable individuals (n=9 each) matched for age and sex. Results were considered significant at p < 0.05 after correction for multiple comparisons.

Results: The PD-MCI converter group had decreased brain volume in the right temporal occipital fusiform cortex (p < 0.05) relative to the PD-NC stable group in the first set of comparisons. No differences were observed in the second set of comparisons.

Conclusion: Changes in brain structure may proceed observable changes in cognition in individuals with PD-MCI. However, given that these changes were only observed in one comparison, more research is needed with larger number of participants to better understand if there are truly differences.

References: 1. Roheger M, Kalbe E & Liepelt-Scarfone I. Progression of cognitive decline in Parkinson’s disease. J Parkinsons Dis 2018; 8: 183-193.
2. Hoogland J, Boel JA, de Bie RMA, et al. Mild cognitive impairment as a risk factor for Parkinson’s disease dementia. Mov Disord 2017; 32: 1056-1065.
3. Litvan I, Goldman JG, Tröster AI, et al. Diagnostic criteria for mild cognitive impairment in Parkinson’s disease: Movement Disorder Society Task Force guidelines. Mov Disord 2012; 27: 349-356.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/an-investigation-of-early-changes-in-the-brain-due-to-mild-cognitive-impairment-in-parkinsons-disease/