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Assessing brain iron and volume of subcortical nuclei in idiopathic rapid eye movement sleep behavior disorder.

STUDY OBJECTIVES
The relationship of iron with cognitive and motor impairment in idiopathic rapid eye movement sleep behavior disorder (iRBD) remains unknown.


METHODS
Twenty-nine (29) patients and 28 healthy controls (HCs) underwent susceptibility weighted imaging and susceptibility mapping. These images were used to evaluate the nigrosome-1 (N1) sign in the substantia nigra (SN), global and regional high-iron (RII) content and volume of subcortical nuclei.


RESULTS
The number of iRBD patients with N1 loss (12) was significantly higher than HCs (2) (P=0.005). Compared with HCs, the iRBD patients had reduced volume of the right caudate nucleus (RCN) (P<0.05, FDR correction) but no significant changes in global and RII iron of the subcortical nuclei (all P>0.05, FDR correction). Multiple regression analysis revealed that: for cognitive function, the RII iron of the RCN was significantly correlated with visuospatial function and the global iron of the right dentate nucleus (RDN) was correlated with memory function; for motor function, the RII iron of the left DN (LDN) and global iron of the left CN correlated with the Alternate-Tap test (left, average), the global iron of the LDN correlated with the Alternate-Tap test (right), and the global iron of the left GP correlated with the 3-meter Timed Up and Go test (all P<0.05, FDR correction).


CONCLUSIONS
Our exploratory analysis found that iRBD patients had a higher incidence of N1 loss and reduced RCN volume after FDR correction. Cognitive and motor impairment were associated with iron deposition in several cerebral nuclei after FDR correction.