Abstract
Background Previous research has shown an association between thalamus and cognition in Parkinson’s disease (PD).
Objectives To investigate the microstructural integrity of the nuclei of the thalamus and relationship with cognition.
Methods Level II Movement Disorder Society Task Force Criteria characterised patients with Parkinson’s disease as cognitively normal (PDN, n=51); with mild cognitive impairment (PD-MCI, n=16) or with dementia (PDD, n=15). Twenty-three healthy control subjects were included for comparison. A k-means clustering approach segmented the thalamus into regions representing nine major nuclei. Volume, fractional anisotropy and mean diffusivity of nuclei were compared between cognitive groups and the relationship with cognitive domain z-scores investigated using hierarchical Bayesian regression models.
Results There was an overall progressive increase in mean diffusivity as cognition deteriorated (PDN: 1.4 µm2/s (95% uncertainty interval [0.2, 2.7]), PDMCI: 2.4 µm2/s [0.8,4.0], PDD: 4.5 µm2/s [2.8, 6.3]). The largest increase was in the lateral dorsal nucleus (PDN: 0.3 µm2/s [-6.7, 7.2], PDMCI: 5.4 µm2/s [-4.7, 16.1], PDD: 14.8 µm2/s [5.0, 25.0]). Fractional anisotropy showed minimal change between cognitive groups (PDN: 0.001 [-0.005, 0,007], PDMCI: −0.005 [-0.013, 0.003], PDD: −0.005 [-0.014, 0.003]). Increase in mean diffusivity of the thalamus is associated with a global decline in cognition, the magnitude of the effect was greatest in lateral dorsal nucleus. Fractional anisotropy only showed evidence of a relationship with cognitive domain scores in the lateral dorsal nucleus.
Conclusions The relationship between lateral dorsal nucleus integrity and cognitive changes is likely due to its primary connectivity with frontal and temporal regions.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
↵i Yale School of Medicine, Yale University, Connecticut, United States of America
Funding Source: This work was supported by a PhD scholarship awarded by The Canterbury Medical Research Foundation Rey Newton Scholarship to Nadia Borlase. The data from this project is part of an ongoing longitudinal study conducted by the New Zealand Brain Research Institute. The longitudinal project is supported by the Canterbury Medical Research Foundation and the New Zealand Neurological Foundation.