Resting-state Functional MRI Study Of Occupational Noise-induced Hearing Loss

Background:Noise pollution seriously interferes with people's normal work and life,reducesthe quality and efficiency,and affects the physical and mental health.Long term worked in the noise environment without taking effective measures to protect the human would cause permanent,irreversible hearing damage,and even lead to serious occupational noise-induced hearing loss(NIHL).Noise induced hearing loss in human has been recognized at home and abroad,and occupational noise-induced hearing loss has become the second most important global occupational hazard.The harm of noise to human body includein both physical and mental.In psychological terms,noisemade people worried,excited,irritable,and even lost the mind.In physiology,noise will produce adverse effects on human auditory system,cardiovascular system,digestive system,nervous system,endocrine system and reproductive system,especially has specific damage to the auditory system.The clinical common audiological examination can only assess the hearing condition,and not explain the changes in the auditory cortex of the brain.Magnetic resonance imaging,especially brain functional magnetic resonance imaging(fMRI)is a noninvasive,repetitive studies of brain morphology and function imaging method.The development of brain functional imaging technology provides the possibility to explore the function of the brain.Objective:Using resting state brain functional magnetic resonance imaging(Rs-fMRI)to detect brain gray matter volume change and of spontaneous cortical activity characteristic in resting state inNIHL patients,and to study the abnormal neural physiological,pathological characteristics and pathological mechanism existed in the brain function and structure.1.Using the voxel-based morphometry(VBM)analysis methods to detect the brain gray matter volume changes among mild NIHL patients(M-NIHL),moderate to severe NIHL patients(MS-NIHL),and the normal control group;to explore the effect of long-term hearing loss on the functional areas of the brain structure and morphology,and further to analyze the correlation with noise exposure time and HamiltonAnxiety(HAMA)Rating scale.2.Using Rs-fMRIto study the change of low frequency fluctuation amplitude(ALFF)and voxel-mirrored homotopic connectivity(VMHC)in NIHL patients,and to analyze the correlation with noise exposure time and Hamilton Anxiety Rating scale.Materials and methods:In accordance with the people's Republic of China National Occupational Health Standard GBZ 49-2007“The Occupational Noise-Induced Hearing Loss Diagnosis”,a collection of diagnosed occupational noise induced hearing loss patients were studiedfrom 2014 February to 2015 December in YTS Hospital,including 27 M-NIHLpatients,15 MS-NIHL patients,and 16normal controls matched with age,and education level with age from 35 to 60 years old.All subjects were male.Hamilton anxiety rating table(HAMA)and mini mental state scale(MMSE)were scored on each subjects.All subjects were underwent routine MR examination and 3D-FSPGR ear brain,brain volume imaging and resting blood oxygenation level dependent BOLD imaging with GE Discovery MR 750 3.0T MRI system.Voxel-based morphometry(VBM)in Metlab SPM software was used to preprocess cerebral gray matter structure MRI imaging,andgray matter density of each individualwas obtained.The differences in gray matter density among the three groups were detectedswith covariance analysis,and age and educational level used as covariates.The absolute value of the different areas of the brain gray matter density,and the variance in three groups of single factor was obtained.Pairwise compare was tested in two groups using LSD test with SPSS statistical software.The relationship both brain gray matter abnormalities and clinical features was explored using bivariate Pearson correlation test.The changed brain areas of ALFF and VMHC was analyzed using REST processing software to compare the differences among three groups of diencephalon functional activities,and the ALFF and VMHC values in changed brain regions was obtained.All data were statistically tested the correlation between the AlFF and VMHC value in changed brain regions with noise exposure time and HAMA score.Results:There were no significant differences in age,education years,HAMA and MMSE scores among the three groups.The occupational noise exposure time of the MS-NIHL was longer than M-NIHL.There were differentin brain gray matter volume of three groups,including the left lateral occipitotemporal gyrus(LLOTG),anterior cingulate yrus(ACG),bilateral angular gyrus(LAG and RAG),precuneus and cerebelum near the midline region.There were higher gray matter densify in LLOTG,precuneus,AG and cerebellar in NIHL patientsthan the normal controls,and higher in ACG in M-NIHL than the control group,while there were lower in ACG in MS-NIHL than the normalcontrols.The gray matter density of MS-NIHL decreased in the anterior area of ACG,LAG and the precuneus.Gray volume differences in brain regions with HAMA scores in each group had no significant correlation.There was negative correlationbetween M-NIHL in ACGwith noise exposure time,and MS-NIHL in the cerebellum in the midline area negative correlation with noise exposure time.Among three groups,ALFF changed brain regions included the right superior temporal gyrus(RSTG),right inferior frontal gyrus(RIFG)and right angular gyrus(RAG).,ALFF values of RSTGin M-NIHL patientsincreased by compared with normal control group,while values of angular gyrusdecreased.In MS-NIHL group,ALFF values in RIFG increased,and RAG reduced.Compared M-NIHL and MS-NIHL,ALFF values increased in RSTG,anddecreasedin RIFG.There was no significant correlation between altered ALFF values and HAMA scores in each group.ALFF values of RSTG in MS-NIHL with noise exposure time had positive correlation.Among three groups,VMHC changed brain areas included inferior frontal gyrus(IFG),paracentral lobule(PCL)and cerebellar hemisphere.Compared with the normal control group,VMHC values of M-NIHL patients increasedin IFG and cerebellum hemisphere,whileVMHC values of the IFG,PCL increased inMS-NIHL.In M-NIHL VMHC values of PCL decreased in comparing with MS-NIHL,while increased in cerebellar hemisphere.VMHC changes,occupation noise exposure time and HAMA score in each group had no significant correlation.Conclusion:1.Comparing NIHL patients with healthy controls,the brain gray matter volume changes in several regions,that suggests long-term noise exposure and hearing loss can lead to human cerebral functional cortex atrophy or hypertrophy,especially in vision,language processing center and part regions of the default mode network.2.Changes of spontaneous activity in the Broca' s area and Wernicke area of NIHL patients,suggests that long-term noise hearing loss may lead to changes in the language function of the central nervous system.The spontaneous activity of resting state increased in M-NIHL patients compared with the healthy control group and the MS-NIHL,suggests that the auditory cortex may be functional reorganization and has a certain dominance hemisphere.3.NIHL patients in resting state exists the brain functional connectivity abnormalities between the two hemispheres,suggests that VMHC can be as an effective assistance and evaluation method to assess the nerve function connection.4.There was no significant correlation between brain gray matter volume,Rs-fMRI brain spontaneous activity,function connection changes with HAMA scores in NIHL,wihle there was a certain correlation with occupational noise exposure time.Thatsuggestsnoise exposure can affect the function of the cortex of the brain.5.VBM and Rs-fMRI can be used to explore the subtle changes in the structure and function of the brain in NIHL patients.VBM and Rs-fMRIcould provide the basis and further neural pathophysiological mechanism researchin order to further understand the effects of NIHL.It is clinical significant in brain function noise deafness prevention and early diagnosis and treatment for NIHL patients,and it would play a guiding role in scientific research,clinical treatment and prognosis,clinical nursing and rehabilitation.