| Objective: With fast development of traffic and construction industries, there shows a gradual yearly increase of traumatic brain injury(TBI) especially mild traumatic brain injury(m TBI). mTBI has minor clinical symptoms and is easily to be ignored by convention imaging modalities that usually manifest negative. In order to provide accurate and comprehensive information for facilitating scientific judgment on clinical diagnosis, treatment and prognosis of mTBI, it is a necessity to deeply study the pathogenesis mechanism of m TBI by using novel functional imaging methods. In the study, we have used diffusion tensor imaging and resting functional MRI to quantitatively analyze the integrity of the white matter, functional net connectivity as well as their relation with cognitive function of mTBI so as to provide general and effective morphologic basis for more accurate treatment program and prognosis assessment.Methods: Diffusion tensor imaging(DTI) can provide more noninvasive information including tissue micriostructure, alignment and injury of the nerve fibers, membrane permeability and temperature that traditional MRI can not cater, which can quantitatively analyze and evaluate the anisotropic changes of the white matter and cater diagnostic information for finding structural and functional changes of m TBI patients. In the study, a systematic study was done on m TBI patients by using MRI diffusion-tensor imaging, quantitatively analyze the integrity of the white matter structure and evaluate the structure of the brain white matter based on tract-based DTI to deeply study the relationship of integrity of the white matter and cognitive function of m TBI patients. In the meantime, amplitude of low frequency fluctuation(ALFF), regional homogeneity(Re Ho) and function connectivity(FC) were used to analyze the resting state f MRI of 25 mTBI patients and 25 healthy volunteers and observe the changes of ALFF, Re Ho and function net connectivity of cognition related brain areas of mTBI patients and analyze the correlation of these parameters with cognition.Results: Conventional T1, T2 weighted and FLAIR MR structure of the mTBI patients showed no obvious abnormalities like bleeding or fracture. The mean education time was(12.84±3.05) years in 25 mTBI patients and(13.89±3.22) years in the control group, with insignificant statistical difference between two groups. Compared with the normal control group, the mTBI patients had decreasing tendency in intelligence score, verbal comprehension index and perceptual reasoning index(PRI), with no obvious difference between two groups. There showed difference only in working memory index(WMI) and processing speed index(PSI) between two groups, with more significant decrease in mTBI patients. There was no obvious difference in MMSE score in both groups. The voxel-based analysis results showed that, in comparison with the normal control group, FA value of the white matter of mTBI patients showed obvious decrease, mainly distributing in the areas including superior longitudinal fasciculus, capsulae, corpus callosum, forceps frontalis and corona radiate; with obvious increase in mean diffusion equation of partial white matter fiber tracts, mainly including rami tractus, superior longitudinal fasciculus and rami capsulae. TBSS results showed that FA value of mTBI patients was different from that the control group. A significant decrease of FA value of superior longitudinal fasciculus, uncinate fasciculus, inferior longitudinal fasciculus and internal capsule, while average diffusion coefficient of white matter fiber MD values were significantly elevated, including the corpus callosum, superior longitudinal fasciculus, uncinate fasciculus and the internal capsule. Statistical analysis showed a significant positive correlation between FA value of the uncinate fasciculus with MMSE score(R2=0.36, P<0.05), a negative correlation between uncinate fasciculus MD value and working memory index(R2=0.51, P<0.05) and a negative correlation between anterior MD value and processing speed index in mTBI patientsd(R2=0.45, P<0.05). There was no significant correlation among FA value, MD value, MMSE score and various intelligence indices in other regions of interest. The resting state functional magnetic resonance imaging results showed that, compared with normal control group, brain regions with significant decrease of Re Ho included left middle frontal gyrus, left inferior frontal gyrus, anterior cingulated and left superior frontal gyrus; the brain regions with significant increase of ReHo included left cuneus, left precuneus and right middle temporal gyrus in mTBI group. The regions with significant decrease of ALFF values including the cingulate gyrus, left middle frontal gyrus, right superior frontal gyrus, right middle frontal gyrus, left superior frontal gyrus; the regions with significant increase of ALFF values included the left occipital gyrus, left precuneus, middle right lingual gyrus and left lingual gyrus in mTBI group. The functional network analysis results showed significant decrease in 15 pairs of function connection of mTBI patients, when the left side of the brain included functional connectivity among left thalamus and left middle frontal gyrus, left inferior frontal gyrus, left inferior temporal gyrus, left parietal lobule, left precuneus, left middle occipital gyrus, functional connectivity among left caudate nucleus, left wedge lobe, left superior frontal gyrus and left middle frontal gyrus; the right side of the brain included functional connectivity between right hippocampus and right moment sulcus, among right thalamus, right angular gyrus, right middle occipital gyrus, right moment sulcus, right lingual gyrus and right middle occipital gyrus. Compared with the normal control group, no significant increase of functional connectivity of all anatomical structures in the brain of m TBI patients. Statistical analysis showed significant positive correlation of Re HO value with MMSE scores in left frontal gyrus of mTBI patients(R2=0.32, P<0.05), positive correlation of cingulate ALFF value with working memory index in m TBI patients(R2=0.42, P<0.05), significant positive correlation of functional connectivity of left thalamus and left middle frontal gyrus with working memory index in mTBI patients(R2=0.38, P<0.05) and significant positive correlation of functional connectivity of right hippocampus and right moment groove with MMSE score(R2=0.34, P<0.05). The other abnormal functional connectivity showed no significant correlation with MMSE score and intelligence.Conclusions: MTBI was significantly associated with cognitive impairment and white matter changes, which can be used as more objective morphological basis to evaluate the cognitive impairment in patients with mTBI. ReHO value of left frontal gyrus positively correlated with MMSE score in mTBI patients, suggesting that significant decrease of Re HO value of left frontal gyrus may lead to cognitive dysfunction and decline of memory in mTBI patients. Cingulate ALFF value positively correlated with working memory index in mTBI patients, suggesting that the decrease of cingulate function may lead to decline of working memory impairment in patients with mTBI. The results of this study found weakened connections between the left thalamus and left middle frontal in patients with mTBI, suggesting that the patients with m TBI lacked in memory and judgment. There is weak functional connection between right hippocampus and right rectangular groove, with significant positive correlation with MMSE score, suggesting that the cognitive impairment of patients with mTBI may be correlated with abnormal information processing of the right hippocampus. Therefore, the diffusion tensor imaging and resting state functional magnetic resonance imaging can show white matter integrity and brain function state of the patients with mTBI, which is different from normal control group and significantly associated with clinical neurocognitive dysfunction, providing more objective imaging basis for making treatment plan and evaluating prognosis. |
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