Objective: To evaluate microstructural characteristics in the cerebello-thalamo-cortical circuit (CTC) of Parkinson’s Disease (PD) patients with different tremor phenotypes.

Background: Tremor is one of the cardinal symptoms of PD. However, microstructural differences at the CTC level between tremor phenotypes have not been explored.

Method: Diffusion Magnetic Resonance Images (dMRI) were performed in 33 PD patients. Brain hemispheres were classified based on contralateral tremor presence, into 4 groups: no tremor (NT, 19), rest tremor (RT, 14), re-emergent tremor (RET, 12) and constant tremor (CT, 11). A total of 10 hemispheres were excluded from the analysis based on the eligibility criteria or the impact of movement on data quality. Voxelwise statistical analysis of the fractional anisotropy (FA), axial diffusivity (AD), mean diffusivity (MD), and radial diffusivity (RD) data was carried out. The CTC was defined using the superior cerebellar and cerebral peduncle structures to define the cerebello-thalamic section, and the posterior limb of the internal capsule and superior corona radiata for the thalamo-cortical section. The percentage of voxels with statistically significant changes (p-value ≤ 0.05) in CTC structures was calculated.

Results: Decreased FA, increased MD and RD were found over 23.21% of voxels in the posterior limb of the internal capsule and superior corona radiata when CT was compared to NT and RT. Also decreased FA and increased RD were observed over 51.20% of voxels in the superior cerebellar peduncle. Increased AD, MD and RD were found over 37.65% of voxels in the superior corona radiata when RET was compared to NT and RT. No statistically significant differences were found in comparisons between NT and RT hemispheres, or between RET and CT, for any diffusion parameter.

Conclusion: Our results suggest that hemispheres contralateral to the RET and CT tremorous hemibody have greater demyelination compared to RT and NT hemispheres. While RET show alterations only in the thalamo-cortical section of the CTC, CT hemispheres show alterations in all segments of the CTC, suggesting that the greater the extent of structural alteration within the circuit, the less impact of movement in mitigating the tremor.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/cerebello-thalamo-cortical-tract-microstructural-changes-in-parkinsons-disease-patients-with-tremor/