Alterations In The Interhemispheric Functional And Structural Integrity In Patients With Traumatic Axonal Injury: A Magnetic Resonance Imaging Study

Objective: To explore the interhemispheric intrinsic connectivity and corpus callosum structural integrity in traumatic axonal injury(TAI) patients and analyze the correlation with clinical variable by using the technologies, including the voxel-mirrored homotopic connectivity(VMHC), based-seed resting-state functional connectivity and diffusion tensor imaging metrics, and to provide a new insight into the pathophysiology mechanism of cognitive disorder in TAI patients.Methods: Twenty-one TAI patients and 22 healthy controls with sex, age and education level matched between April 2013 and October 2015 were recruited, and obtained the data of resting-state fMRI, high resolution T1 weighted imaging and DTI, conventional computed tomography(CT) and routine MRI, susceptibility weighted imaging(SWI). Data processing include:(1) Resting state fMRI data pre-processing was performed using the DPARSFA、SPM8 based on MATLAB platform. The calculation of VMHC value and the analysis of two sample t-test bewteen two groups were performed by DPARSFA software.(2) Seed-based functional connectivity was completed by placing the regions of interest(ROIs) in areas that exhibited VMHC difference with whole brain voxel and analysed by using two sample t-test bewteen two groups(P < 0.05,GRF correction).(3) FSL5.0 was applied to extract the DTI parameters(FA value, MD value, RD value, AD value) of the corpus callosum.(4) All subjects underwent clinical rating scale(GCS、MMSE、DRS、BDI、MAS、ABS、CDR、HAMA、ADL). The general condition and the clinical score between TAI group and HCs group were analyzed with IBM SPSS 19.0 software for two-sample t test. Clinical rating scale and VMHC abnormal area in TAI group were computed for Pearson correlation analysis in a voxel-wise manner(P < 0.05, GRF correction).Results :(1) The scores of GCS、MMSE、DRS、BDI、MAS、ABS、CDR、HAMA 、ADL in TAI group were higher than HCs(P<0.05).(2) Compared with the controls, the TAI patients exhibited significantly decreased VMHC in several pair-clusters, including the medial prefrontal cortex(Brodmann area(BA) 10), superior temporal gyrus(BA22), middle temporal gyrus(BA 21/38), inferior frontal gyrus(BA11/47), posterior cingulate cortex /calcarine cortex(BA7/31), thalamus and cerebellum posterior lobe.(3) Subsequent seed-based functional connectivity analysis revealed widely disrupted whole-brain functional connectivity, particularly the areas subserving the default, salience, integrative and executive systems.(4) Compared with the controls, the TAI patients exhibited significantly decreased FA in the genu, body, splenium of corpus callosum, and increased MD, RD in genu of corpus callosum, as well as decreased AD, RD in the body, splenium of corpus callosum.(5) Significantly negative correlations were observed between the BDI score and VMHC of the inferior frontal gyrus and basal ganglia in the TAI patient group. A significantly negative correlation was also observed between the CDR score and VMHC in the thalamus. Furthermore, we observed a significantly positive correlation between the MMSE score and VMHC in the caudate.Conclusions:(1) TAI is associated with interhemispheric coordination disorder, suggesting decreased interhemispheric integration and interaction.(2) TAI couples with widely disrupted functional connectivity, including the default, salience, integrative, and executive functions.(3) Alteration of corpus callosum, may provides potential structure foundation for interhemispheric interaction deficit in TAI patients.(4) Decreased interhemispheric interactions and extensively whole-brain disrupted functional connectivity, further provide a new pathophysiology evidence of cognitive impairment in the TAI patients, and provide theory foundation for the functional and structural impairment of other subtype in patients with TBI.