**5. Conclusions**

In conclusion, T1ρ MRI may be a valuable biomarker for monitoring disease progression and evaluating future clinical trials in JOHD. This novel imaging technique allows for high-resolution, quantitative analysis of subcortical metabolic changes. T1ρ MRI abnormalities in JOHD participants were found within the caudate, putamen, globus pallidus, and thalamus, and mean T1ρ relaxation times within these regions were predictive of disease severity and motor deficits.

**Author Contributions:** Conceptualization, A.V.T., J.L.S., A.J.K., J.E.B., V.A.M. and P.C.N.; methodology, A.V.T., J.L.S., A.J.K., J.E.B. and V.A.M.; software, A.V.T. and J.L.S.; validation, A.V.T., J.L.S. and P.C.N.; formal analysis, A.V.T., J.L.S. and P.C.N.; investigation, E.A.E. and P.C.N.; resources, V.A.M. and P.C.N.; data curation, E.A.E. and P.C.N.; writing—original draft preparation, A.V.T., J.L.S. and A.J.K.; writing—review and editing, J.E.B., E.A.E., V.A.M. and P.C.N.; visualization, J.L.S.; supervision, P.C.N.; project administration, P.C.N.; funding acquisition, P.C.N. All authors have read and agreed to the published version of the manuscript.

**Funding:** This study was supported by the National Institute of Neurological Disorders and Stroke (NINDS; R01NS055903). The APC was funded by the National Institute of Neurological Disorders and Stroke (NINDS; R01NS055903).

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
