Brain Micro-structural Abnormalities In Patients With Idiopathic Rapid Eye Movement Sleep Behavior Disorder

Objective:Rapid eye movement(REM)sleep behavior disorder(RBD)is a parasomnia characterized by the loss of normal skeletal muscle atonia during REM sleep with prominent motor activity accompanying dreaming,which usually cause injures to themselves or their spouses.Idiopathic RBD(iRBD)is defined by the occurrence of RBD in the absence of any other neurological disorders.However,the specific pathogenesis of iRBD still remains unclear,considered as a possible precursor to neurodegenerative diseases,especially a-synuclein degenerative diseases,which can be used to diagnose parkinson’s disease,multiple sy stem atrophy and other neurological degenerative diseases early.In this study,we explore the abnormal alterations in the brain of patients with iRBD by using voxel based morphometry(VBM)and diffusion tensor imaging(DTI),trying to investigate the possible pathophysiological mechanisms of iRBD,as well as the relationship between iRBD and neurodegenerative diseases.Methods:A total of 15 patients with iRBD diagnosed in Guangdong General Hospital from January 2016 to July 2017 were enrolled in this study.20 gender,age and education matched healthy control subjects were recruited from the community.All patients with iRBD were stopped with nervous system drugs for at least 12 hours in order to reduce the effects of pharmacological actions of nervous system drugs for the neurological activity in patients.The mini-mental state scale(MMSE)score were used to assess the cognitive status of the subjects.We use Philips 3.0 T(Ingenia)of superconducting magnetic resonance.imaging system to scan whole brain of all subjects.VBM was used to measure the three-dimensional T1 anatomical image and the original data of diffusion tensor imaging was also analyzed by voxel based analysis method(VBA).The SPM 8 software was used to analyze the DTI and VBM parameters of the two groups.The difference was statistically significant when P<0.05.The results were displayed by using XjView software and the specific parameters include gray matter volume(GMV),white matter volume(WMV),fractional anisotropy(FA),mean diffusivity(MD).The clinical datas of the two groups were analyzed by SPSS software.Results:The MMSE score of iRBD group was lower than that of the healthy control group,and the difference was statistically significant.Compared with the healthy controls,VBM found that gray matter volume of iRBD group reduced in the left thalamus,right supramarginal gyrus,while white matter volume reduced in the left rectus gyrus,left fusiform gyrus,left middle occipital gyrus,left middle frontal gyrus.There were no regions with increased gray matter volume and white matter volume of iRBD.Voxel based analysis of diffusion tensor imaging showed that MD of iRBD group are increased in left superior temporal pole gyrus,left middle temporal pole gyrus,right parahippocampal gyrus,right rectus gyrus,left median frontal orbit gyrus.There were no regions with decreased MD and abnormal FA of iRBD.Conclusion:Our study found that iRBD prefer to elderly men,prone to cognitive dysfunction.We study the brain structure in patients with iRBD by using VBM and VBA of DTI,found that patients with iRBD develop a wide range of changes in brain structure.The structural abnormalities of the brain in the frontal lobe,temporal lobe,occipital lobe,thalamus and parahippocampal are closely related with the occurrence of iRBD,possibly because of the damage in the regulatory loop of REM sleep,providing imaging evidence for the pathophysiological mechanism of iRBD.The abnormal alterations in the frontal lobe,parahippocampal are similar to the brain changes in parkinson’s disease,multiple system atrophy and other nervous system degenerative diseases,suggesting that iRBD maybe correlated to nervous system degenerative diseases,as a possible precursor of neurodegenerative diseases.