| Objective: Traumatic brain injury(TBI)is the leading a major cause of disability and death in patients in the word,more than 50 million people have a TBI each year.China had a population represents approximately 18% of the world population and nationwide data for the epidemiology of TBI have not been available to this day,but the overall mortality and disability of TBI is similar to the reported rates abroad.At present,neuroimaging plays a key role in the diagnosis,treatment and prognosis prediction of TBI and has advanced beyond structural imaging to functional tissue characterization including cerebral perfusion.In recent years,the use of brain perfusion imaging to study TBI has become a hot topic.The present study aimed to investigate the early phase changes of cerebral hemodynamics and blood brain barrier(BBB)permeability under different surgical intervention methods following TBI in rabbits by computed tomography perfusion imaging.We hope to further study the changes of cerebral hemo-dynamics after TBI,and to explore the value of different surgical intervention methods in improving cerebral hemodynamics and prognosis,so as to enrich the understanding and help to provide new ideas for the treatment of TBI.Methods 1)Construction of animal model.Following abdominal anesthesia in healthy adult New Zealand white rabbits,an aperture 5 mm in diameter was made in the upper part of left interparietal bone using a mini-dental grinding drill.The animal dura mater was carefully stripped off from the inner skull plate and a self-made pressurized balloon which is in turn connect to a micro-infusion pump was palced into the epidural space.A needle was then inserted into the aperture of the dura mater and a intracranial pressure(ICP)monitoring probe was implanted into the brain tissue.Controlling the micro-infusion pump to inject normal saline into the pressurized ballon at the speed of 10ml/h and monitoring the change of ICP until ICP reaches 25 mm Hg.2)Animal grouping.The animals were randomly assigned into four groups(n=10 rabbits/group).In the control group,the animals were not infused with normal saline.For the common/controlled decompression groups,the infusion of normal saline was performed as described in the TBI group.In the common decompression group,normal saline was immediately pumped out from the balloon catheter,before animal were monitored for another 15 min.In the controlled decompression group,normal saline was slowly pumped out from the balloon catheter,stopping for 5 min when the ICP value had declined to 20 mm Hg,15 mm Hg and 10 mm Hg before the saline was pumped out compuletely.3)Conventional CT and CT perfusion(CTP)scanning.The coronal CT scanning was performed before CTP.After conventional CT scanning,CTP was performed at the basal ganglia and images were immediately uploaded onto workatation following data acquisition.4)Measurement of cerebral perfusion parameters.The cerebral middle cerebral arter-y and the superior sagittal sinus were automatically set as the input artery and out-put vein,respectively.A parametric diagram reflecting blood perfusion in cerebral tissues was constructed.The diagram was evaluated by a senior neuroradiologist,who elect each region of interest(ROI)in size at the bilateral temporal lobes and basal ganglion and measured the regional cerebral blood flow(rCBF),regional cerebral blood volume(rCBV),mean transit time(MTT).5)Determination of BBB permeability.Animals were injected with Evans Blue(EB)dye through the ear vein 1 h prior to sacrifice which were perfusion with normal saline.Brain tissues from the bilateral temporal lobs were carefully removed from the animals following sacrifice and the content of EB was determined according to the determination process.Ultrastructure of brain tissue was observed under transmission electron microscopy.6)Statistical analysis.Data were analyzed using IBM SPSS statistics version 23.0.P<0.05 was considered to indicate a statistically significant difference.Results1)A clear cerebral sulcus and cerebral gyrus could be observed in the control group.The CT value in the frontal lobe of the white matter was calculated to be 29-30.Following compression,the cerebral sulcus was absent from the CT images,and the cerebral gyrus was unclear2)Compared with those in the control group,the local cerebral rCBF and rCBV values were demonstratively decreased in the TBI,common decompression and controlled decompression groups,suggesting reduced blood flow to the rabbit brain tissues.In addition,prolonged MTTs were observed in the TBI,common decompression,and controlled decompression groups,with the most notable MTT extension detected in the common decompression group.3)The rCBF and rCBV values of the bilateral temporal lobes and basal ganglion in the TBI,common decompression and controlled decompression groups were significantly lower compared with the control group(P<0.01).Comparison between the TBI,common decompression and controlled decompression groups also revealed significant differences in the rCBF and rCBV values of the bilateral temporal lobes and basal ganglion(P<0.01).Notably,controlled decompression slightly alleviated TBI-induced reductions of rCBF and rCBV values in the bilateral temporal lobes and basal ganglion compared with TBI group(P<0.01).Common decompression only rescued the TBI-induced decrease in rCBV in the basal ganglion compared with TBI group(P<0.01)and worsened the other parameter index values.Compared with the control group,the MTT values of the bilateral temporal lobes and basal ganglion in the TBI,common decompression,and controlled decompression groups were significantly increased(P<0.01).4)Significantly increased BBB permeability was detected in the TBI,common decompression and controlled decompression groups compared with control and there were also significant differences among the three groups.5)Under electron microscopy,ischemic damage,vacuole formation in the cytoplasm and enlargement of the gap between some nerve cells and small vessels were observed after TBI in rabbits.In the conventional decompression group,the ischemic damage of neurons was further aggravated,the number of neurons was reduced and arranged irregularly,nuclear pyknosis was accompanied by red staining,interstitial edema was obvious,and the morphological changes of neurons in the controlled decompression group were similar to those in the compression group.6)Under transmission electron microscopy,the organelles in the TBI group were slightly dilated,the extracellular space was slightly enlarged,the microvascular endothelium was proliferated and the tight junction was damaged.In common decompression,organelles dilated,intracellular and extracellular edema,microvascul-ar endothelial proliferatio and tight junction damaged was obvious.The degree of damage of organelles and blood vessels in controlled decompression group was slightly than that in common decompression group.Conclusions The present study demonstrated that CTP could be used to analyze local early phase changes in cerebral hemodynamics after TBI induction in rabbits.TBI induced significant reductions in rCBF and rCBV,prolonged MTT and greatly increased BBB permeability in rabbits.Controlled decompression was more effective at preventing these abnormalities in cerebral hemodynamics through partially improving the impaired mechanism of cerebral vascular autoregulation following TBI injury induction.These findings provide valuable insights for understanding the use of CTP to evaluate therapeutic outcomes and cerebral hemodynamics in patients with TBI. |
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