Objective: To elucidate the association between autonomic symptoms and Parkinson’s disease (PD) subgroups stratified by k-means clustering of thalamic subnuclear volumes measured by MRI.

Background: Ascending fibers conveying motor, sensory, and limbic information project to the thalamus, which comprises approximately 30 distinct subnuclei. Thalamic subnuclei are defined by their cytoarchitecture and their afferent and efferent projections, and may be relevant to the pathophysiology of PD.

Method: Sixty-five patients with early-onset PD (EOPD; 36 men; median age 52.8 years, interquartile range [IQR] 48.2-57.2) and 89 patients with late-onset PD (LOPD; 49 men; median age 68.3 years, IQR 64.7-72.5) were recruited at Juntendo University. EOPD was defined as an age at onset of <50 years, and LOPD as ≥50 years. Autonomic dysfunction was assessed with the Scales for Outcomes in Parkinson’s Disease-Autonomic Dysfunction (SCOPA-AUT). Thalamic subnuclei volumes were calculated using FreeSurfer (https://surfer.nmr.mgh.harvard.edu/), and the mean of the right and left volumes with adjustment for whole thalamus volume was used for analysis. K-means clustering was performed. The optimal number of clusters was determined using multiple cluster-validity indices including second difference D-index. Differences between clusters were assessed using the Kruskal-Wallis test followed by Dunn’s post hoc test. Spearman correlation analysis was used to evaluate associations between SCOPA-AUT scores and thalamic subnuclei volumes.

Results: SCOPA-AUT scores were not significantly different across clusters in either the EOPD (p = 0.455) or the LOPD (p = 0.506). SCOPA-AUT scores were significantly correlated with the inferior pulvinar nucleus (PuI; rs = -0.43, p = 0.003) and the paratenial nucleus (Pt; rs = 0.40, p = 0.006) in EOPD and with the lateral pulvinar nucleus (PuL; rs = 0.36, p = 0.004).

Conclusion: These findings suggest that these subnuclei, may reflect alterations in afferent inputs associated with dysautonomia in PD and may serve as candidate imaging biomarkers. External validation is needed.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/specific-thalamic-subnuclei-volumes-associate-with-autonomic-dysfunction-in-parkinsons-disease/