Brain White Matter Structural Alteration In Primary Hemifacial Spasm:A Diffusion Tensor Imaging Study

Objective: To explore the abnormal of white matter structure in the brain of HFS patients.First of all,to analyze the changes in white matter structure of the whole brain by using the tract-based spatial statistics（TBSS）method.In addition,to investigate microstructural abnormalities in the corpus callosum substructure region of HFS patients by using the region of interest（ROI）analysis method.Methods: 29 p HFS patients and 29 healthy controls with matching age,gender,and education were selected.All subjects received 3.0T MR brain DTI scan.（1）TBSS method was used to analyze the changes in white matter structure of the whole brain and obtain the white matter fibrers exhibiting significant intergroup differences.The fractional anisotropy（FA）,mean diffusivity（MD）,axial diffusivity（AD）,and radial diffusivity（RD）of these areas were abstracted.Correlation analysis was conducted to analyze the correlation between these diffusion metrics and clinical variables（disease duration,spasm severity）.（2）ROI method was used to analyze the changes of white matter structure in the corpus callosum.The corpus callosum was reconstructed and divided into three substructure regions（genu,body,and splenium）according to MNI standard brain template.The fractional anisotropy（FA）,mean diffusivity（MD）,axial diffusivity（AD）,and radial diffusivity（RD）of substructure regions in the corpus callosum of p HFS patients were measured and the statistical analyses were performed.Correlation analysis was conducted to analyze the correlation between diffusion metrics exhibiting significant intergroup differences and clinical variables.Results:（1）The results of TBSS analysis: compared with the HC group,the p HFS group exhibited significantly lower FA in the forceps minor（FM）,bilateral anterior thalamic radiation（ATR）,and right superior longitudinal fasciculus（SLF）.Cohen grading scale of the p HFS group was negatively correlated with FA of FM.（2）The results of ROI analysis: compared with the HC group,the p HFS group exhibited significantly lower FA,as well as higher RD and MD in the genu,the body,and the whole corpus callosum.The disease duration and Cohen grading scale of the p HFS group were negatively correlated with FA of the body and the Cohen grading scale of the p HFS group was negatively correlated with FA of the whole corpus callosum.Conclusion:（1）Based on TBSS analysis,the damages to white matter fiber tracts in p HFS patients were found,including FM,bilateral ATR and right SLF.Aggravated symptoms may lead to increased damages in the white matter fibers between the genu of the corpus callosum and the prefrontal cortex.（2）Based on ROI analysis,the corpus callosum substructure region of p HFS patients had extensive damages,presenting as the damages of myelin sheath in the genu and the body of corpus callosum.The corpus-callosum-cortex circuit,especially the white matter fibers through the genu and the body of corpus callosum,plays an essential role in the neuropathological mechanism of p HFS.The point that the corpus-callosum-cortex circuit can be regarded as a special region related with disease progression of p HFS may provide guidance for treatments of p HFS.