The Study Of Arcuate Fasciculus Injury And Language Dysfunction After Acute Mild Traumatic Brain Injury

Part Ⅰ Arcuate Fasciculus Subsegment Impairments Distinctly Associated With Memory And Language Deficits In Acute Mild Traumatic Brain Injury PatientsObjective:To explore arcuate fasciculus(AF)subsegment alteration by automated fiber quantification(AFQ)in the early acute phase(<48h after trauma)of mild traumatic brain injury(mTBI),and the influence of internal subsegments of AF properties with verbal memory and language function in mTBI patients.Method:In this study,twenty-five acute mTBI patients(<48h after trauma)and thirty-three age-sex-and education-matched healthy controls(HCs)were included.To assess the verbal memory and language function,all participants finished cognitive examinations as follows.Language was assessed by Verbal Fluency Test(VFT)and Boston Naming Test(BNT).Verbal memory was tested by the Rey Auditory Verbal Learning Test(RAVLT),including total recall and delayed recall tests.Working memory was evaluated by the Digit Span Forward and Backward Tests.Both 3D MPRAGE T1WI image and diffusion tensor image(DTI)were acquired to investigate the altered diffusion properties of the AF tracts.Comparisons of the diffusion properties and neuropsychological scores between the mTBI patients and HCs were performed using analysis of covariance(ANCOVA),adjusting age,gender and education years.The results were corrected for multiple comparisons using the false discovery rate(FDR)procedure for diffusion properties.Partial correlation analyses were performed to investigate the relationship between the neuropsychological scores and imaging measures with gender,age,and education level controlled.Result:Reduced verbal memory(RAVLT total recall:P=0.003,F=18.975;RAVLT delayed recall:P=0.001,F=22.38)and language(VFT:P=0.021,F=13.975;BNT:P=0.035,F=11.463)were shown in the patients group compared to the HCs.The mTBI patients showed significantly higher mean Fractional anisotropy(FA)and lower mean Radial diffusivity(RD)in the right AF tract compared to the HCs(FA:PFDR=0.031;RD:PFDR=0.028).The node-wise comparisons showed significantly increased FA and decreased RD values at the terminal portions of the right AF tract(FA:nodes 16-23 and 68-95,PFDR=[0.021,0.05);RD:nodes 1-31 and 68-95,PFDR=[0.017,0.05))in the patients group.On the other hand,there was no difference in either the mean(FA:PFDR=0.125;RD:PFDR=0.167)or intra-tract diffusion measures in the left AF tract.For the temporal subsegment(nodes 68 to 95)of the right AF,which showed increased FA in the patients group,the mean FA was positively correlated with the RAVLT total recall score(r=0.428,P=0.043)in the HCs,In mTBI patients,negative correlations between the FA measure and memory function scores were shown(RAVLT total recall score:r=-0.538,P=0.032;RAVLT delayed recall score:r=-0.528,P=0.035).On the other hand,the mean FA across the disrupted frontal portion(nodes 16 to 23)of the right AF was negatively correlated with the BNT score(r=-0.463 P=0.029)in HCs,while this correlation was diminished in the patients group(r=0.085,P=0.746).Conclusion:AFQ technology is useful to detect the damage of the AF substructural integrity which locates near the intersections of white matter and gray matter area after acute phase of mTBI.Our study provides new insights into the understanding of the structural heterogeneity of the AF tracts as well as the distinct associations of its subsegment impairments with verbal memory and language function deficits in acute mTBI patients.Part II Arcuate Fasciculus Functional Connectivity Alteration Correlated With Memory And Language Impairments After Acute Mild Traumatic Brain InjuryObjective:To explore the functional connectivity pattern change following AF substructures injury with language dysfunction in the early acute phase of mTBI.Method:Twenty-five acute mTBI patients(<48h after trauma)and thirty-three agesex-and education-matched HCs were enrolled.RAVLT,Digit Span Forward and Backward Tests,VFT and BNT measures was finished to assess the verbal memory and language function.Both 3D MPRAGE T1WI image and resting state functional MRI(rs-fMRI)image were acquired.The right inferior frontal gyrus(IFG)and superior temporal gyrus(STG)cortical regions which anatomically connects by the right AF was selected as the seeds for the rs-fMRI analysis.To investigate the within-group whole brain functional connectivity(FC)patterns,voxel-wise one-sample t-tests were conducted on the individual FC maps for both mTBI patients and HCs.The thresholds for statistical significance were set at corrected P<0.05 and cluster size>228 voxels with AlphaSim multiple comparison correction(M=1000 iterations)using Resting-State FMRI Data Analysis Toolkit(REST v1.8).Two-sample t-tests were applied to determine the between-group FC differences.The thresholds were set at corrected P<0.05 and cluster size>228 voxels following the same correction parameters as above.Partial correlation analyses were performed to investigate the relationship between the neuropsychological scores and imaging measures for both mTBI patients and HCs with gender,age,and education level controlled.Result:Reduced verbal memory(RAVLT total recall:P=0.003,F=18.975;RAVLT delayed recall:P=0.001,F=22.38)and language(VFT:P=0.021,F=13.975;BNT:P=0.035,F=11.463)were shown in the patients group compared to the HCs.When using the IFG as the seed,both groups exhibited higher FC values compared to the global mean value within the central executive network,including the dorsolateral prefrontal cortex.The areas showing lower FC values were located in inferior parietal lobe.When using the STG as the seed,higher FC values were found in precuneus areas in both groups,while reduced FC values were shown in the medial prefrontal cortex and angular gyrus.Compared to the HCs,the mTBI patients showed significantly increased FC in the cuneus and decreased FCs in the parahippocampal gyrus and middle occipital gyrus(MOG)when using the IFG as the seed.When using the STG as the seed region,the patients showed increased FCs in the median cingulate and paracingulate gyri as well as decreased FCs in the precuneus and angular area.In the HCs group,a significantly negative correlation was found between subjects BNT score and the FC between the IFG and MOG area(r=0.617,P=0.006).For the mTBI patients,there was a significantly positive correlation between the RAVLT delayed recall score with the FC between IFG and MOG(r=0.562,P=0.036).Conclusion:As the damage of the AF substructural integrity,the association between the FC of IFG and MOG with BNT score in HCs was disrupted in the mTBI patients.Our research provides new understanding of structure and function of AF tracts as well as the distinct roles of different subsegments in contribution to the language and verbal memory deficits present in acute mTBI patients.