Objective: To investigate thalamic subnuclei volume and macrostructural white matter changes in Parkinson’s disease (PD) depression.

Background: Depression is a common neuropsychiatric feature of Parkinson’s Disease (PD) but an understanding of its neural correlates remains limited. The thalamus may be relevant as previous work demonstrated functional connectivity and white matter microstructural changes in PD depression. We used a novel thalamic segmentation method to investigate thalamic subnuclei volume and macrostructural white matter changes in PD depression.

Method: 76 participants with PD underwent structural and diffusion weighted imaging. We used a thalamic segmentation method, which is a Bayesian segmentation algorithm based on a histologically derived probabilistic thalamic atlas, to divides each thalamus into its 25 constituent subnuclei.
We assessed longitudinal change in subnuclei volumes and white matter macrostructure by extracting volumes and using fixel based analyses to calculate mean fibre cross sections (FC) for afferent and efferent fibres at each subnuclei, at baseline and 18-month follow-up. We used a generalised linear mixed model to evaluate the relationship between depression and both nuclei volume and mean FC for all 50 subnuclei.

Results: Depression scores were associated with significant decreases in mean FC across 43 of the 50 thalamic subnuclei. Additionally, depression scores were significantly associated with lower right pulvinar anterior (PuA) nucleus volume at follow-up but this did not survive FDR correction for multiple comparisons (β= -1.32 (SE=0.52), p=0.01, q=0.50). When co-varying for antidepressant use, the association between depression and lower right PuA volume remained significant, and in this model, antidepressant use significantly predicted higher right PuA volumes (β= 12.27 (SE=5.34), p=0.02).

Conclusion: We demonstrate that depression is associated with right PuA volume loss and widespread thalamic white matter macrostructural changes. Further, we found that antidepressants may protect against right PuA volume loss. Overall, our work has identified the right PuA as a potentially relevant neural correlate of PD depression.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/thalamic-white-matter-macrostructure-and-subnuclei-volumes-in-parkinsons-disease-depression/