Objective: In this study, we tested the hypothesis that free water is elevated in the posterior substantia nigra of idiopathic rapid eye movement sleep behaviour disorder, which is considered a prodromal stage of synucleinopathy.

Background: Imaging markers that are sensitive to neurodegeneration in the substantia nigra are critically needed for future disease-modifying trials. Previous studies have demonstrated the utility of posterior substantia nigra free water as a marker of progression in Parkinson’s disease.

Method: We applied free-water imaging to 32 healthy controls, 34 idiopathic rapid eye movement sleep behaviour disorder patients and 38 Parkinson’s disease patients. And 18 healthy controls and 22 idiopathic rapid eye movement sleep behaviour disorder patients were followed up completing longitudinal free-water imaging. Free-water values in the substantia nigra were calculated for each individual and compared among groups. We tested the associations between posterior substantia nigra free water and uptake of striatal dopamine transporter in the idiopathic rapid eye movement sleep behaviour disorder.

Results: Free-water values in the posterior substantia nigra were significantly higher in the idiopathic rapid eye movement sleep behaviour disorder patients than in the healthy controls but significantly lower in the idiopathic rapid eye movement sleep behaviour disorder patients than in the Parkinson’s disease patients. In addition, we observed significantly negative associations between posterior substantia nigra free-water values and dopamine transporter striatal binding ratios in the idiopathic rapid eye movement sleep behaviour disorder patients. Longitudinal free-water imaging analyses were conducted with a linear mixed-effects model, and showed a significant group × time interaction in posterior substantia nigra, identifying increased mean free-water values in posterior substantia nigra of iRBD over time.

Conclusion: These results demonstrate that free water in the posterior substantia nigra is a valid imaging marker of neurodegeneration in idiopathic rapid eye movement sleep behaviour disorder, which has the potential to be used as an indicator in disease-modifying trials.

« Back to MDS Virtual Congress 2021

MDS Abstracts - https://www.mdsabstracts.org/abstract/increased-free-water-in-the-substantia-nigra-in-idiopathic-rem-sleep-behaviour-disorder/