Location And Mechanism Of Microstructural Changes In Five Subregions Of The Corpus Callosum In Minimal Hepatic Encephalopathy:A DTI Study

Objective: To use different diffusion tensor imaging(DTI)indices to further understand microstructural changes and the underlying pathophysiology of these changes in the entire corpus callosum(CC)and its subregions in minimal hepatic encephalopathy(MHE).Methods: DTI was performed in fifteen MHE patients,fifteen liver cirrhosis patients without HE(NMHE)and sixteen healthy controls(HC).DTI scans were performed after Psychometric Hepatic Encephalopathy Score(PHES).After Brain GPS(vesion 1.0)recomputing the magnetic field gradient,the factional anisotropy(FA),axial diffusivity(AD/?1),radial diffusivity(RD),?2,and ?3 maps were obtained after eddy current correction and head motion correction using DTI Studio(CMRM,Johns Hopkins Medical Institute,USA)software.FA,AD,RD were extracted and the mean diffusivity(MD)was calculated.The demographic data,DTI indice of five subregions of CC and total CC,blood ammonia,and neuropsychological test among groups were analyzed by one-way analysis of variance(ANOVA),multiple analyses of variance(MANOVA),correlation analysis and other statistical analysis.Results: Compared with HCs,NMHE and MHE patients showed significant abnormalities in CC-2,CC-4,CC-5 and the entire CC.MHE patients showed decreased FA and AD with increased RD in CC-5,increased MD and RD in CC-4,decreased FA with increased RD and MD in the entire CC and increased RD in CC-2(P < 0.05).Neuropsychological performance and blood ammonia levels were not significantly correlated with the DTI indices(P>0.05),but RD showed a positive correlation trend with number connection test A(NCT-A)in CC-5.On the contrary,FA and AD demonstrated negative correlation trend with NCT-A in CC-5.Meanwhile,we found a negative correlation trend between RD and digit-symbol test(DST)in CC-2.RD and MD showed a negative correlation trend with DST in the entire CC.There was a significant positive correlation between RD and MD in CC-4 and in the entire CC(P < 0.05).Conclusion: Our study demonstrated microstructural changes in subregions of the CC in MHE that may induce the impairments in interhemispheric coordination and communication.Our results may provide insight into the mechanism underlying MHE.