弥漫性轴突损伤早期超微结构改变

目的通过观察弥漫性轴突损伤(DAI)患者伤后早期轴突的超微结构变化以探索DAI的发生机理.方法对12例DAI患者的14份活体脑组织标本进行透射电镜检查.结果 DAI患者在伤后早期可发生多方面的轴突改变,包括(1)轴突的细胞骨架破坏;(2)轴膜改变;(3)膜性细胞器的变化;(4)髓鞘的改变;(5)轴突出现肿胀和离断,轴突近侧断端呈现球状.结论在DAI的发生中,可能有多种机理参与.推测,在受到足够强的外力作用时,一些管径较细的轴突可能会立即断裂;其它受损轴突则会出现进行性的延迟性轴突断裂.在此演化过程中,细胞骨架破坏和轴膜受损继而通透性改变可能是造成轴突局灶性轴浆转运障碍最终离断的最重要的因素.     

Early detection of axonal injury after human head trauma using immunocytochemistry for β-amyloid precursor protein

Severe non-missile head injury commonly results in a form of brain damage known as diffuse axonal injury (DAI). The histological diagnosis of DAI is made by silver staining for the presence of axonal retraction balls. This feature takes about 24 h to develop and does not allow for the early histological diagnosis of DAI. We have used immunocytochemistry for the -amyloid precursor protein (APP) as a marker for axonal injury in formalin-fixed, paraffin-embedded sections of human brain. Axonal APP immunoreativity was present in all cases which had survived for 3 h or more. This was true even where the degree of head injury did not appear to be severe, supporting the theory that DAI is a severe form of a more common phenomenon of axonal injury which occurs after cerebral trauma. APP immunoreactivity was also found in some non-head injured cases and so cannot be considered to be a specific marker for trauma. The results show that APP immunocytochemistry may be useful in the detection of traumatic axonal injury in its early stages, before the formation of axonal retraction balls, provided care is taken to exclude other causes of such immunoreactivity.Supported by the Home Office Policy Advisory Board for Forensic Pathology (UK)     

直线加速度所致的猫弥漫性轴突损伤

目的：为了解直线加速度在颅脑损伤特别是在弥漫性轴突损伤（ＤＡＩ）中的作用。方法：用一套撞击装置对２６只猫进行实验。结果：直线加速度可以导致几乎所有类型的颅脑损伤，包括颅骨骨折、蛛网膜下腔出血、硬膜下血肿、硬膜外血肿、脑挫伤、脑干损伤，特别是ＤＡＩ。ＤＡＩ的特征性改变－轴突回缩球在２４小时内死亡的动物脑标本中看不到，２４小时后可见到，７２小时则多而典型，７天时仍然存在。结论：凡能使脑的神经纤维受到广泛剪力和（或）张力的任何形式的外部作用均可产生ＤＡＩ。     

弥漫性轴索损伤的影像与临床分析

目的探讨弥漫性轴索损伤的影像学及临床特点,为诊断和治疗提供参考。方法对47例弥漫性轴索损伤患者的临床资料及影像学进行回顾性分析。结果随访3～12个月,根据格拉斯哥预后评分（GOS）：恢复良好12例,中残14例,重残8例,植物生存3例,死亡10例。不同影像学分级组的预后无显著差异。结论弥漫性轴索损伤是临床上常见的颅脑损伤类型,其诊断主要根据临床和影像学表现;目前CT和常规MRI尚不能作为诊断的必要条件,也不能作为准确评估患者预后的独立依据。     

弥漫性轴突损伤胆碱能纤维改变的实验研究

目的通过大鼠弥漫性脑损伤模型观察海马及乳头体内的轴突损伤,了解轴突损伤后上述结构中胆碱酯酶纤维的变化,探讨轴突损伤与伤后记忆功能障碍的相关性.方法用Marmarou介绍的落体打击装置致伤动物,对海马和乳头体区脑组织进行胆碱酯酶(AChE)纤维染色.结果该模型较好地模拟了轴突损伤的表现,简便实用.在这个模型中轴突损伤的最常见部位为桥脑基底部和小脑上脚,其次为大脑半球白质、海马和乳头体.海马结构内含有大量胆碱酯酶阳性染色纤维.与对照组相比中,损伤10天海马CA1区,CA3区,齿状回分子层和乳头体内纤维密度明显低于对照组大鼠(P＜0.01).结论大鼠损伤后海马区和乳头体内胆碱酯酶阳性纤维明显减少,这可能是弥漫性轴突损伤病人记忆功能损害的原因.     

Assessing connectivity related injury burden in diffuse traumatic brain injury

Many of the clinical and behavioral manifestations of traumatic brain injury (TBI) are thought to arise from disruption to the structural network of the brain due to diffuse axonal injury (DAI). However, a principled way of summarizing diffuse connectivity alterations to quantify injury burden is lacking. In this study, we developed a connectome injury score, Disruption Index of the Structural Connectome (DISC), which summarizes the cumulative effects of TBI‐induced connectivity abnormalities across the entire brain. Forty patients with moderate‐to‐severe TBI examined at 3 months postinjury and 35 uninjured healthy controls underwent magnetic resonance imaging with diffusion tensor imaging, and completed behavioral assessment including global clinical outcome measures and neuropsychological tests. TBI patients were selected to maximize the likelihood of DAI in the absence of large focal brain lesions. We found that hub‐like regions, with high betweenness centrality, were most likely to be impaired as a result of diffuse TBI. Clustering of participants revealed a subgroup of TBI patients with similar connectivity abnormality profiles who exhibited relatively poor cognitive performance. Among TBI patients, DISC was significantly correlated with post‐traumatic amnesia, verbal learning, executive function, and processing speed. Our experiments jointly demonstrated that assessing structural connectivity alterations may be useful in development of patient‐oriented diagnostic and prognostic tools. Hum Brain Mapp 38:2913–2922, 2017. © 2017 Wiley Periodicals, Inc.     

脑弥漫性轴索损伤轴索内钙超载及钙拮抗剂的治疗作用

目的探讨脑弥漫性轴索损伤(DAI)轴索内Ca2+超载及Ca2+拮抗剂的治疗作用.方法 SD大鼠14只,分损伤组、用药组(伤后立即静注尼莫通)、对照组.用自制头颅瞬间侧向旋转装置,制作大鼠DAI模型.伤后2～24小时取延髓组织,行Ca2+电镜细胞化学处理(草酸钾-焦锑酸钾法)和观察.结果 (1)损伤组神经轴索髓鞘板层断裂、间隙扩大,轴膜与髓鞘脱离,细胞器边聚,轴浆空泡形成,线粒体稀少.受损髓鞘内有大量细小钙颗粒,髓鞘损害程度与钙颗粒数量呈正相关;伤后晚期轴浆内可见粗大钙颗粒.神经元胞体及血管内皮细胞空泡化,也有钙颗粒沉着,内皮细胞管腔面出现微绒毛.(2)用药组轴索髓鞘损伤趋于局部,线粒体数量、形态、分布近于正常,髓鞘及轴浆钙颗粒罕见,神经元胞体及血管内皮细胞空泡变明显减轻.结论 DAI中轴索存在Ca2+超载,这是导致DAI发生发展的重要因素;Ca2+拮抗剂尼莫通可改善DAI.     

Graded model of diffuse axonal injury for studying head injury‐induced cognitive dysfunction in rats

Diffuse axonal injury (DAI) plays a major role in the development of cognitive dysfunction, emotional difficulties and behavioral disturbances in patients following closed head injury, even when they have no definite abnormalities on conventional MRI. This study aimed to develop a highly controlled and reproducible model for DAI that simulates post‐traumatic cognitive dysfunction in humans. Sprague‐Dawley (SD) rats were subjected to impact acceleration head injury, using a pneumatic impact targeted to a steel disc centered onto their skull. The severity of injury was graded as three levels by adjusting the driving pressure at 60, 70 or 80 pounds per square inch. In vivo MRI was obtained 2 days post‐injury. Cognitive function was evaluated using the Morris water maze at 1 and 2 weeks post‐injury. HE staining and immunohistochemistry were performed to assess neuronal and axonal damages after 2 weeks. MRI demonstrated that this model induced no gross structural modification in the brain. The degree and duration of cognitive dysfunction were dependent on the force of impact. Histological analysis revealed the force‐dependent damage of the neurons and microtubule‐associated protein 2‐positive axons in the neocortex. Hippocampal damage was much less pronounced and was not linked to cognitive dysfunction. This is the first report that precisely evaluates the threshold of impact energy to lead to neocortical damage and cognitive dysfunction in rodents. This model would be suitable for clarifying the complex mechanisms of post‐traumatic brain damage and testing novel therapeutic approaches against post‐traumatic cognitive dysfunction due to diffuse axonal damage.     

The occurrence of diffuse axonal injury in the brain：associated with the accumulation and clearance of myelin debris

The accumulation of myelin debris may be a major contributor to the inlfammatory response after diffuse axonal injury. In this study, we examined the accumulation and clearance of myelin debris in a rat model of diffuse axonal injury. Oil Red O staining was performed on sections from the cerebral cortex, hippocampus and brain stem to identify the myelin debris. Seven days after diffuse axonal injury, many Oil Red O-stained particles were observed in the cerebral cortex, hippocampus and brain stem. In the cerebral cortex and hippocampus, the amount of myelin debris peaked at 14 days after injury, and decreased signiifcantly at 28 days. In the brain stem, the amount of myelin debris peaked at 7 days after injury, and decreased signiifcantly at 14 and 28 days. In the cortex and hippocampus, some myelin debris could still be observed at 28 days after diffuse axonal injury. Our ifndings suggest that myelin debris may persist in the rat central ner-vous system after diffuse axonal injury, which would hinder recovery.     

弥漫性轴突损伤形态学改变的实验研究

目的　观察弥漫性轴突损伤的常见部位, 病理改变过程, 以及其发生原因和机制。探讨其与临床的相关性。方法　用 Ｍａｒｍａｒｏｕ 的落体打击装置致伤动物, 大鼠脑组织标本在光镜和电镜下观察。结果　轴突回缩球密度在桥脑基底部和小脑上脚最高。伤后轴突内的微丝、微管结构紊乱, 轴突肿胀。伤后３ 天, 多数肿胀的轴突断裂, 形成轴突回缩球。１ 小时组轴突内钙颗粒数量是对照组的１７ 倍, 提示钙的内流。结论　本实验中弥漫性轴突损伤的最常见部位是桥脑基底部和小脑上脚。轴突损伤的过程为： 轴突内结构的紊乱, 轴突肿胀及断裂。轴突损伤的主要发生原因和机制可能是细胞外钙的内流。在伤后１２ 小时以内, 损伤轴突尚未断裂, 可能仍存在可逆性, 这可能是临床上有效治疗的最佳时机。     

弥漫性轴索损伤的CT影像分析

目的探讨CT对弥漫性轴索损伤（DAI）的诊断价值。方法回顾性分析临床确诊的56例DAI患者的CT特点及临床表现。结果CT表现：①脑灰白质交界区、胼胝体及其周围、脑干、基底节区多发或单发小出血灶；②弥漫性白质密度减低，灰白质界线不清，双侧脑室和脑池受压、变窄或消失；③合并硬膜下血肿、脑室及蛛网膜下腔出血、骨折等。临床表达为深昏迷，GCS评分≤6～7分，生命指征紊乱，瞳孔散大，光反射消失。结论CT影像结合临床表现对DAI有较高的诊断价值。     

Ubiquitin marks the reactive swellings of diffuse axonal injury

Summary Ubiquitin is a protein that targets proteins for non-lysosomal degradation. It has been found to be present in a number of inclusions characteristic of neurodegenerative diseases. Using the fluid percussion model of diffuse axonal injury (DAI), we now report that the reactive axonal swellings and the retraction balls produced in this model stain positively with antiubiquitin immunohistochemistry. Furthermore, the affected axons become ubiquitin positive quickly (with-in the first 6 h after injury). Anti-ubiquitin immunohistochemistry compares well with the recently reported ability of antibodies to low molecular weight neurofilament proteins to demonstrate reactive axonal change in DAI, and it could provide additional clues to the pathogenesis of axonal transection.Supported by a grant from the NINDS (NS01230) and by a grant from the Baptist Memorial Health Care Foundation     

The usefulness of diffusion tensor imaging in detection of diffuse axonal injury in a patient with head trauma

Diffuse axonal injury is the predominant mechanism of injuries in patients with traumatic brain injury. Neither conventional brain computed tomography nor magnetic resonance imaging has shown sufficient sensitivity in the diagnosis of diffuse axonal injury. In the current study, we attempted to demonstrate the usefulness of diffusion tensor imaging in the detection of lesion sites of diffuse axonal injury in a patient with head trauma who had been misdiagnosed as having a stroke. A 44-year-old man fell from a height of about 2 m. Brain magnetic resonance imaging (32 months after onset) showed leukomalactic lesions in the isthmus of the corpus callosum and the left temporal lobe. He presented with mild quadriparesis, intentional tremor of both hands, and trunkal ataxia. From diffusion tensor imaging results of 33 months after traumatic brain injury onset, we found diffuse axonal injury in the right corticospinal tract (centrum semiovale, pons), both fornices (columns and crus), and both inferior cerebellar peduncles (cerebellar portions). We think that diffusion tensor imaging could be a useful tool in the detection of lesion sites of diffuse axonal injury in patients with head trauma.     

DWI及SWI序列对弥漫性轴索损伤的诊断价值

目的探讨弥散加权（DWI）和磁敏感加权（SWI）序列在脑弥漫性轴索损伤（DAI）中的诊断价值。方法回顾性分析17例经临床和影像证实的急性DAI患者的MRI资料,包括常规T1WI、T2WI、液体衰减反转恢复（FLAIR）序列以及DWI和SWI序列,分别比较各序列对DAI非出血性和出血性病灶的检出数目,并分析其分布特点和信号特征。结果DAI病灶主要分布在白质、皮髓交界区、基底节、胼胝体、脑干及小脑等区域。DWI对非出血性DAI病灶的检出率最高,与其它序列的差异有统计学意义（P〈0．05）。而SWI对出血性DAI病灶的检出率最高,与其它序列的差异也均有统计学意义（P〈0．05）。结论DWI和SWI序列联合应用大大提高DAI病灶的检出率,为临床早期诊断提供更加可靠的影像学依据,应作为MRI检查DAI的常规和首选序列。     

纳洛酮干预对大鼠弥漫性轴索损伤后突触素表达的影响

目的探讨弥漫性轴索损伤(diffuse axonal injury,DAI)后纳洛酮干预对突触素表达的影响。方法 99只Wistar雄性大鼠随机分为对照组、损伤组、纳洛酮干预组,对照组为假损伤,后两组采用改良的Marmarou大鼠颅脑DAI模型。伤后分别检测突触素表达变化情况,同时评价行为学功能和观察病理变化。结果伤后6 h、24 h,对照组行为学评分显著高于纳洛酮干预组(均P<0.01),同时纳洛酮干预组显著高于损伤组(均P<0.05)。大鼠致伤后,损伤组及纳洛酮干预组基底池、颅底可见轻度蛛网膜下腔出血,但无大面积或局灶性挫裂伤。光镜下见损伤组伤后24 h病理损害最严重,尼氏体数目显著减少、体积变小,甚至溶解消失,纳洛酮干预组上述改变有不同程度减轻。DAI后,突触素免疫阳性反应产物平均积分光密度(IOD)值分析表明:对照组IOD值高于损伤组(P<0.01)及纳洛酮干预组(P<0.05);损伤组DAI后突触素表达下降,24 h表现最为明显(P<0.01);纳洛酮干预组表达下降程度减轻,伤后6～72 h突触素表达显著高于损伤组(P<0.05),且24 h差异最明显(P<0.01)。结论早期纳洛酮干预对DAI后大...     

脑弥漫性轴索损伤的特点及临床诊断

目的　探讨脑弥漫性轴索损伤 (DAI)的特点及临床诊断标准。　　方法　对 58例DAI患者行头颅CT检查 ,其中 3 9例同时行MRI,并分析其临床特点。　　结果　 75 9?I由交通事故致伤 ;患者伤后立即并持续昏迷 ;70 7%的病人无明显颅压增高 ;CT检查 63 8%有异常发现 ,MRI的诊断价值比CT高 ;DAI病变 89 7%在脑的深部及中轴结构 ;该病预后差 ,病死率为 53 5%。　　结论　根据临床特点、CT和MRI检查结果提出DAI的临床诊断标准     

Neuronal free Caand BBB permeability and ultrastructure in head injury with secondary insult

Objective: To study changes in free calcium (Ca²⁺), neuronal and blood–brain barrier (BBB) permeability and ultrastructure in brain after diffuse axonal injury (DAI) with secondary brain insults (SBIs).Method: One hundred and twenty Sprague-Dawley (SD) rats were randomised into control, DAI alone and DAI with SBI groups which were sub-divided into 5 groups that were 0.5 h, 2 h, 12 h, 24 h, 48 h post trauma. The animal models of DAI and DAI with SBI have been described before (2). Fluorescence probe Fluo-3/Am was used to measure free Ca²⁺in neurons. Laser scan microscopy was used to detect fluorescence intensity. After the animals were anesthetized, Lanthanum nitrate liquid was used for intracardiac perfusion to assess BBB permeability. Under the transmission electron microscope, changes in cerebral ultrastructure and BBB permeability were observed.Results: The fluorescence intensity was weak in the control. The concentration of free Ca²⁺in neurons was obviously increased at 30 min after brain injury, reached a peak at 12 h–24 h (P< 0.01), and appeared to decrease at 48 h after injury. In the DAI alone group, BBB tight junction opening with particles of Lanthanum nitrate outside the vessels was found at 30min after injury, and peaked at 24 h. In DAI with SBI, the changes in ultrastructure and BBB permeability were more severe than that in the DAI alone group at the same time interval. The shape of the fluorescence concentration curve was basically the same for both kinds of brain injury. The intensity of fluorescence in DAI with SBI was higher than that in the DAI alone group at the same time interval (P< 0.05).Conclusion: In DAI alone and DAI with SBI, Ca²⁺overload and BBB permeability changes interact and both play important roles in the aggravation of brain damage.     

Midline brain injury in the immature rat induces sustained cognitive deficits, bihemispheric axonal injury and neurodegeneration

Infants and children less than 4 years old suffer chronic cognitive deficits following mild, moderate or severe diffuse traumatic brain injury (TBI). It has been suggested that the underlying neuropathologic basis for behavioral deficits following severe TBI is acute brain swelling, subarachnoid hemorrhage and axonal injury. To better understand mechanisms of cognitive dysfunction in mild-moderate TBI, a closed head injury model of midline TBI in the immature rat was developed. Following an impact over the midline suture of the intact skull, 17-day-old rats exhibited short apnea times (3–15 s), did not require ventilatory support and suffered no mortality, suggestive of mild TBI. Compared to un-injured rats, brain-injured rats exhibited significant learning deficits over the first week post-injury (p < 0.0005), and, significant learning (p < 0.005) and memory deficits (p < 0.05) in the third post-injury week. Between 6 and 72 h, blood–brain barrier breakdown, extensive traumatic axonal injury in the subcortical white matter and thalamus, and focal areas of neurodegeneration in the cortex and hippocampus were observed in both hemispheres of the injured brain. At 8 to 18 days post-injury, reactive astrocytosis in the cortex, axonal degeneration in the subcortical white matter tracts, and degeneration of neuronal cell bodies and processes in the thalamus of both hemispheres were observed; however, cortical volumes were not different between un-injured and injured rat brains. These data suggest that diffuse TBI in the immature rat can lead to ongoing degeneration of both cell soma and axonal compartments of neurons, which may contribute, in part, to the observed sustained cognitive deficits.     

Toluene abuse causes diffuse central nervous system white matter changes

We describe the findings of magnetic resonance imaging (MRI) of the brain in 6 chronic toluene vapor abusers and the neuropathological findings in 1 abuser not studied by MRI. MRI in 6 chronic toluene abusers revealed the following abnormalities: (1) diffuse cerebral, cerebellar, and brainstem atrophy; (2) loss of differentiation between the gray and white matter throughout the central nervous system; and (3) increased periventricular white matter signal intensity on T2-weighted images. Another chronic toluene abuser (MRI not performed) died as a result of acute toluene overdose. The brain displayed diffuse, ill-defined myelin pallor, maximal in cerebellar, periventricular, and deep cerebral white matter. Neurons were preserved throughout, axonal swelling or beading was not seen, gliosis was minimal, and occasional, scant perivascular macrophage collections were seen. Taken in concert, these findings suggest that the pathological and MRI abnormalities are due to either increased water content of the white matter or subtle toluene-induced metabolic changes in myelin.