Hippocampai Neuronal Damage And Axonal Injury Detected By Proton Magnetic Resonance Chemical Shift Imaging (~1H CSI) After Traumatic Brain Injury

Background:Magnetic Resonance Spectroscopy(MRS) has been shown to be asensitive approach for metabolic abnormalities in the brain after TBI, whichprovide the evidence of early diagnosis for the TBI.Objective: In the study, we performed1H CSI in swine head injury model. Theability of CSI to detect neurochemical abnormalities in the hippocampus andwhite matter was evaluated. We also compared these neurochemical alterationsdetected by1H CSI with histology to evaluate the role of CSI in revealing brainpathology post-TBI.Methods: Twenty miniature swine were used for this study. Ten pigs werestudied with MRS at two timepoints (1h postinjury, and3-day postinjury). Tenanimals was uninjured and served as a normal control. Diffuse axonal injury andfocal cortical contusion were induced in the pig. All animals were performedmulti-voxel CSI scanning. Metabolic ratios for NAA/Cho and NAA/Cr weredetermined. At3-day postinjury, animals were sacrificed, and hippocampalpathology and axonal damage throughout the brain were evaluated.Results: A significant decline in NAA/Cho and NAA/Cr in bilateralhippocampi was observed between preinjury and three-day postinjury. In thebasal ganglion, the mean decrease of NAA/Cho and NAA/Cr at either1hpostinjury or three-day postinjury compared with preinjury was significant.Hippocampal neuronal and axonal injuries were observed in the regions where metabolic abnormalities were noted.Conclusions: TBI induces cerebral metabolite changes in both hippocampusand basal ganglia, which are demonstrated by decreased NAA/Cho ratios. Thesemetabolic abnormalities may represent neuronal damage and axonal injury inhistology.1H CSI is able to detect these neurochemical alterations that can not bediscovered by routine imaging.