Objective: To characterize brain microstructural integrity, iron loads, and functional connectivity in 10 idiopathic rapid eye movement sleep behavior disorder (RBD), 10 Parkinson’s disease (PD) and 10 age-matched healthy subjects..

Background: iRBD evolves into PD or another synucleinopathy ∼90% of cases. Thus, it is crucial to have sensitive imaging methods that can detect changes in different brain regions in those with iRBD as they progress towards PD.

Methods: Ten individuals with PD (67±6 years, 5F/5M, UPDRS=39), ten iRBD subjects (64±7 years, 5F/5M, UPDRS=15) and ten age-matched healthy controls (58±6 years, 4F/6M) underwent 3T MRI. Adiabatic T1ρ, T2ρ and RAFF4 measurements were collected from 30 AC-PC aligned slices covering brainstems and basal ganglia, while T1-weighted and T2-weighted images, DTI, T2* and rsfMRI were collected in a whole-brain fashion. MRI relaxation and DTI parameters were calculated from 12 regions of interest (ROIs) relevant for PD, and compared among the subject groups. Functional connectivity measures were extracted using seed analyses from 3 out of 12 ROIs (regions of primary analysis), namely the caudate, substantia nigra (SN) and midbrain.

Results: Statistically significant differences of MRI relaxation and DTI parameters among groups were observed in regions of primary analysis including SN, caudate, and midbrain. Interesting differences of MRI parameters were simultaneously observed also in other brain regions including amygdala and parahippocampal gyrus. Overall the observations were consistent with neuronal degeneration and iron accumulation in multiple brain regions, with gradual trends across controls vs iRB vs PD possibly suggesting progression of iRBD into PD. In addition, we observed significant differences between controls and PD of functional connectivity measures in the networks associated with SN and midbrain, in agreement with previous observations of disrupted nigrostriatal connectivity induced by iRBD and PD.

Conclusions: MRI modalities detected group differences in multiple subcortical brain regions of iRBD and PD subjects vs controls. Our multimodality approach may prove useful in evaluating neuronal loss, white matter changes, iron deposition and changes in functional connectivity that characterize the evolution of iRBD into PD.

Submitted for presentation at the Annual Meeting of ISMRM May 2016.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/mri-signatures-of-the-brain-of-parkinsons-disease-and-idiopathic-rem-sleep-behavioral-disorder-subjects/