Magnetic Resonance Imaging-Based Brain Morphological Studies For Tinnitus Patients

Tinnitus prevalence augments with age and is expected to increase in the future due to increased aging population and noise exposure.Patients suffered from persistent tinnitus often associate with anxiety,distress and other tinnitus-related abnormalities.The quality of life and job performance for tinnitus patients are seriously affected.It is significantly important for clinicians to understand better the mechanisms and characteristics of tinnitus,which can assist greatly for early diagnosis and treatment of tinnitus,and to alleviate the influence of tinnitus symptom on patients.In recent years,neuroscience research has gradually become the focus of basic sciences and clinical research.The rapid development of neuroimaging technologies also provided new insight for neuroscience research.In this study,morphological changes of the brain of tinnitus patients were explored with the use of noninvasive magnetic resonance imaging data,with a specific focus on the brain morphological alterations of pulsatile tinnitus patients and non-pulsatile tinnitus patients.In order to find the characteristics of neuroanatomical alterations of pulsatile tinnitus patients,the changes of gray matter volume in patients with unilateral pulsatile tinnitus during their early stage of symptom were studied using voxel-based morphometry(VBM)analysis.The steps of spatial normalization,segmentation and smooth were used in data pre-processing.Two-sample tow-tailed t-test and Pearson's correlation analysis were performed in statistical analysis.In the second part of this work,machine learning technique was used in differentiating non-pulsatile tinnitus patients from normal controls.Using hybrid feature selection algorithm and SVM classifier,61 brain regions related to tinnitus were obtained,which were characterized by gray matter volume in each brain area.From this study,eight typical characteristic brain regions were extracted and the neuroimaging biomarkers strongly associated with tinnitus symptoms were summarized.It was found that patients with unilateral pulsatile tinnitus had significant increase of gray matter(GM)volume in bilateral superior temporal gyrus,as compared with the normal controls.However,the left cerebellum posterior lobe,left frontal superior orbital lobe(gyrus rectus),right middle occipital gyrus(MOG),and bilateral putamen showed significantly decrease in their volumes.The correlation between the brain volume of MOG and THI score was not statistically significant.This suggests that pulsatile tinnitus can lead to changes in the anatomical of the brain,both the auditory pathway(cerebellum posterior lobe)and the visual pathway(the middle occipital gyrus)will be influenced by tinnitus.The brain is working as a whole organ when processing auditory messages.This is the first study demonstrated the features of neuroanatomical changes in patients with early stage of pulsatile tinnitus.Morphological study of non-pulsatile tinnitus found that the combination of bilateral hypothalamus,left superior frontal gyrus,right RMG,right insula,right inferior parietal lobule(IPL),and left superior temporal gyrus(STG)(2 neighbored nodes)can significantly differentiate tinnitus patients from healthy controls.The area under the receiver operating characteristic curve(AUC)was 72% for the classification.Therefore,these eight brain regions can be used as neuroimaging biomarkers in tinnitus patients and contribute to the understanding of the neuroanatomical alteration features for tinnitus patients.