Objective: Voxel-based analysis was applied to MRI parameters of iron content (transverse relaxation rate, R2*), microstructural integrity including mean diffusivity (MD) and fractional anisotropy (FA) as well as gray and white matter volume of patients with Richardson’s syndrome (PSP-RS), progressive supranuclear palsy-parkinsonism (PSP-P), Parkinson variant of multiple system atrophy (MSA-P) and Parkinson’s disease(PD) to detect disease specific patterns in the brainstem and cerebellum that may be helpful for the differential diagnosis.

Background: Manually driven ROI analyses revealed distinct MRI signal changes within the infratentorial region of patients with PD, PSP-RS, PSP-P and MSA-P but are limited by rater dependent apriori knowledge of both brain anatomy and focal degenerative patterns.

Methods: 15 PSP-RS, 13 PSP-P, 17 MSA-P and 20 PD patients were compared with 25 age-matched healthy controls (HC). Statistical parametric mapping using the spatially unbiased infratentorial template (SUIT), a high-resolution atlas template of the human cerebellum and brainstem was applied to identify focal changes of MRI parameters in an objective and observer-independent fashion.

Results: Significant volume loss in the mesencephalic tegmentum, superior cerebellar peduncle (SCP), dentate nucleus and dorsal part of the pons were evident in the total PSP cohort compared to MSA-P, PD and HC, respectively (p<0.001). Relative to the PSP-P cohort, the PSP-RS cohort showed significantly decreased FA and increased MD values in the SCP (p<0.001). Significantly increased iron content was identified only in the substantia nigra of PSP-RS patients compared to HC (p<0.001). MSA-P patients showed significant volume loss, decreased FA and increased MD measures throughout the pontocerebellar region compared to PSP, PD and HC, respectively (p<0.001). In the PSP-RS patients, FA decreases within the dentatorubrothalamic tract correlated inversely with the UPDRS subscore related to postural instability and gait disturbance (r=-0.67; p=0.012).

Conclusions: Microstructural dysintegrity of the dentatorubrothalamic tract was significantly more pronounced in PSP-RS compared to PSP-P and associated with the clinical measures of postural instability. DTI could be a useful marker to identify PSP-RS patients in the routine clinical setting.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/multimodal-voxel-based-analysis-of-the-infratentorial-brain-region-in-richardsons-syndrome-progressive-supranuclear-palsy-parkinsonism-parkinson-variant-of-multiple-system-atrophy-and-parkinsons-d/