Objective: To identify the neuroanatomical basis of early cognitive change in Parkinson’s disease (PD).

Background: 50% of PD patients develop dementia within 10 years of diagnosis[1, 2], but the neural correlates of the earliest changes associated with cognitive decline are unclear. Previous studies have shown inconsistent atrophy patterns in PD, particularly in early disease stages [3-5]. By analysing the cortical thickness from MRI scans, we investigated whether a pattern could be detected when accounting for increased risk of dementia, as predicted by established algorithms [6, 7].

Method: 109 patients recently diagnosed with PD and 37 age and gender-matched controls without eye-disease were recruited. T1 MRI scans and neuropsychological measures were collected. Risk of cognitive involvement was calculated using two different clinical algorithms – one that combined age at onset, MMSE, education, motor score, gender and depression [6]; and another that combined age, UPSIT, RBDSQ, and depression [7]. Cortical reconstructions were performed within Freesurfer-v6.0, and cortical thickness measures between patient and control groups were compared. Correlations between cortical thickness and cognitive risk were measured using GLM (General Linear Model), and results were corrected for multiple comparisons.

Results: Bonferroni post-hoc comparisons demonstrated that patient and control groups were well matched in gender, age, education, and cognitive performance. Our results showed no differences in cortical thickness between the patient and control group, but when accounting for risk of dementia, atrophy patterns were found within the PD group. Atrophy in the precuneus, a region known to be linked with visuospatial abilities [8-10] was the most significant correlation with increased cognitive risk, which was consistent between the two different risk algorithms.

Conclusion: We identified several regions of atrophy associated with a higher risk of dementia, with the precuneus being the most significant result with both cognitive risk scores. The known involvement in visuospatial ability of this brain region provides further evidence that patients with early involvement of visual processing regions are at higher risk of dementia.

References: 1. Perez, F., et al., Risk of dementia in an elderly population of Parkinson ’ s disease patients : A 15-year population-based study. 2012. 8: p. 463-469. 2. Williams-gray, C.H., et al., The CamPaIGN study of Parkinson ’ s disease : 10-year outlook in an incident population-based cohort. 2013: p. 1258-1264. 3. Song, S.K., et al., The pattern of cortical atrophy in patients with Parkinson’s disease according to cognitive status. Mov Disord, 2011. 26(2): p. 289-96. 4. Melzer, T.R., et al., Grey matter atrophy in cognitively impaired Parkinson’s disease. J Neurol Neurosurg Psychiatry, 2012. 83(2): p. 188-94. 5. Mak, E., et al., Baseline and longitudinal grey matter changes in newly diagnosed Parkinson’s disease: ICICLE-PD study. Brain : a journal of neurology, 2015. 138(Pt 10): p. 2974-2986. 6. Liu, G., et al., Prediction of cognition in Parkinson’s disease with a clinical- genetic score: a longitudinal analysis of nine cohorts. 2018. 16: p. 620-629. 7. Schrag, A., et al., Clinical variables and biomarkers in prediction of cognitive impairment in patients with newly diagnosed Parkinson’s disease: a cohort study. The Lancet. Neurology, 2017. 16(1): p. 66-75. 8. Gardini, S., et al., Visuo-Spatial Imagery Impairment in Posterior Cortical Atrophy: A Cognitive and SPECT Study %J Behavioural Neurology. 2011. 24(2). 9. Ranganath, C. and M. Ritchey, Two cortical systems for memory-guided behaviour. Nature Reviews Neuroscience, 2012. 13: p. 713. 10. Dhindsa, K., et al., Examining the role of the temporo-parietal network in memory, imagery, and viewpoint transformations. Frontiers in human neuroscience, 2014. 8: p. 709-709.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/neuroanatomical-correlates-of-early-cognitive-change-in-parkinsons-disease/