Neurofilament 68 Expression And Diffusion Tensor Image In Rats Brainstem After Diffuse Axonal Injury

Objective:Diffuse axonal injury(DAI)is difficult to diagnose or characterize non-invasively. Diffusiontensor imaging (DTI) has shown promise in detecting DAI. This study investigates the changesof neurofilament 68 expression and DTI in rats brainstem after diffuse axonal injury. Wehypothesized that neurofilament 68 (NF 68) expression were correlated with apparent diffusioncoefficient (ADC) and fractional anisotropy (FA) measurements in diffusion tensor imaging afterDAI.Materials and Methods:Forty-two Sprague Dawley ( SD) rats were randomly divided into 6 groups, one control groupand five injury groups. The injury groups models of DAI were made by Marmarou Device. Fiveseparate parallel DAI groups of 7 rats per group were imaged by GE 1.5T MR scanner atpre-injury and re-imaged at 3h,6h,12h,24h,72h post-injury respectively. Rats in DAI groupwere sacrificed for histology immediately after the scan. A control group of 7 rats was imagedand sacrificed for histology but not injured. Each group was studied by conventional MRimaging, diffusion tensor imaging ( GE 1.5T scanner) and histologically examination includingHE,silver staining, and immunohistochemistry of NF68. The results of conventional MRI andDTI were compared with the changes of histopathology findingsResults:FA value of the injury groups brainstems began to decline at 3 h post injury, and reached thelowest value at 72h: 0.255±0.005. ADC values of the injury group brainstems graduallyincreased after injury and peaked at 12h (1.548±0.200), then decreased gradually and reached thelowest value at 72h. In the brainstems of injury groups,axon swelling, axon retraction ball werefound by histopathological observation. The expression of NF68 in the brainstems tended toincrease at 3h post injury, showed significant changes with arriving at the peak at 24h (IOD 0.172±0.020), and began to decrease from 24h post injury. There were significant difference inADC, morphological changes of axonal and NF68 expression in brainstem between DAI groupand control subjects.The mean ADC and FA values from injury groups significantly differed from those ofthe normal controls and there were significant differences among the mean FAvalues for the injury groups (P < 0.05). The IOD of NF68 expression for injury groups werenegative correlated with FA values within 24h post injury (r = -0.494, P < 0.01);and there werepositive correlation between IOD and ADC values before 12h post injury (r = 0.504, P < 0.01).All data were analyzed using Statistica 15.0 (StatSoft).ConclusionConclusion:DTI is more sensitive than conventional imaging methods for detecting axonal injury. NF68may be involved in the pathological processes of brainstem with DAI. ADC values and FAvalues in brainstem were correlated with NF68 expression within 24h post injury, which supportthe hypothesis that DTI play an important role in the early diagnosis, treatment and prognosisimprovement for DAI.