Traumatic axonal damage in the brain can be detected using beta-APP immunohistochemistry within 35 min after head injury to human adults

Immunohistochemistry staining for beta-amyloid precursor protein (beta-APP) is a sensitive method to detect early axonal damage in traumatic brain injury, which was previously estimated to be of minimum 60-90 min after head injury. We present seven cases of well-documented posttraumatic survival of 35-60 min where beta-APP detects early axonal damage. Cases were selected from routine work where documentation about survival is judged to be accurate. These are divided into three groups: group 1: severe head injury (n = 7) with documented survival between 35 and 60 min. Group 2: severe head injury (n = 4) with documented survival of less than 30 min. Group 3: cases (n = 4) where death was not due to head injury but survival is documented between 45 and 109 min. The brains were fixed in formalin for 4 weeks and six regions (frontal lobe with anterior corpus callosum, parietal lobe with deep white matter, basal ganglia with posterior limb of internal capsule, cerebellum with white matter and middle cerebellar peduncle and pons with basis pontis and superior cerebellar peduncle) were sampled. All blocks were stained for haematoxylin and eosin and beta-APP and selected ones for CD68, using antigen retrieval method. In group 1 sections revealed beta-APP immunoreactivity in forms of small globules and granules and occasionally as thin and short filaments. These were detected in the pons, corpus callosum, internal capsule and cerebral white matter, with some variation in localization and intensity. In groups 2 and 3 all the sections were negative for beta-APP staining. None of the cases showed evidence of severe brain swelling, increased intracranial pressure, ischaemia or infection. Using the antigen retrieval method, beta-APP immunohistochemistry can detect axonal damage within 35 min after severe head injury. These results may have an implication in the consideration of minimal survival time after traumatic head injury in medico-legal practice.     

The diagnosis of diffuse axonal injury: implications for forensic practice

The diagnosis of diffuse axonal injury (DAI), which may be of considerable importance in forensic medicine, necessitates widespread sampling of the brain for histology. Because a limited sampling method for screening brains for axonal damage would be of value for medico‐legal work, the authors have tested the findings of an earlier study which suggested that a standard set of three blocks from above and below the tentorium could reliably be used in routine practice as a basis for the diagnosis of DAI. A series of 22 previously diagnosed cases of DAI, with a range of survival times, was studied using immunohistochemistry with antibodies to β‐amyloid precursor protein (βAPP), the microglial‐associated antigen CD68 (PG‐M1) and for GFAP. Strict histological criteria were used to assess traumatic damage, and the evolution of the histological changes with increasing survival is described. In four cases, the sampling scheme employed yielded evidence of axonal damage in only one block, and a diagnosis of DAI could have been made in only 13/22 cases. In six of the shortest surviving cases, βAPP positivity in the corpus callosum and brainstem outlined areas of early ischaemia, as well as of traumatic damage, so that interpretation of immunolabelling was not always clear‐cut. The findings suggest that DAI cannot be reliably diagnosed on a restricted number of blocks from vulnerable areas, and that the use of βAPP and PG‐M1 immunocytochemistry may bring interpretative problems that can only be resolved by taking a larger series of tissue samples for histology.     

The nature of transmission in prion diseases

Replicating biological information is usually stored only within nucleic acid. The existence of 'strains' of agent in prion disease (scrapie, BSE, CJD) has been taken to indicate an independent genome within the transmissible agent. Other replicable information exists, however, both in biology and elsewhere, including, for example, the 'meme' (the neural correlate of ideas which replicate in human brains by communication) and the computer virus. From this broader viewpoint, we explore the possibility that 'strain' differences in prion disease reflect biological information stored within the prion protein rather than in nucleic acid. Much of the disease variation in mice (used as evidence for strain differences) can be accounted for by the primary structures of the prion protein of the host (the experimentally infected mouse) and the donor mouse (from which infectious tissue is taken). Information determining residual disease variation (when these factors have been excluded) may reside in different conformational states of host prion protein. Prion protein can adopt different conformational and glycosylation states. The information which these states contain is only partially conserved on transmission between animals, permitting the appearance of both 'strain stability' and 'strain mutation'. Different sources of replicating, biological information including information in the 'agent' (the abnormal form of prion protein) and in the host prion gene ( PRNP ) are in evolutionary competition. We argue that, in the prion diseases, replicating information is not carried in nucleic acid in either the host or the 'agent' but is carried within the conformational state of the abnormal form of prion protein.     

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.     

Dysautonomia after severe traumatic brain injury

Background: Dysautonomia after traumatic brain injury (TBI) is characterized by episodes of increased heart rate, respiratory rate, temperature, blood pressure, muscle tone, decorticate or decerebrate posturing, and profuse sweating. This study addresses the incidence of dysautonomia after severe TBI, the clinical variables that are associated with dysautonomia, and the functional outcome of patients with dysautonomia. Methods: A historic cohort study in patients with severe TBI [Glasgow Coma Scale (GCS) ≤ 8 on admission]. Results: Seventy‐six of 119 patients survived and were eligible for follow‐up. The incidence of dysautonomia was 11.8%. Episodes of dysautonomia were prevalent during a mean period of 20.1 days (range 3–68) and were often initiated by discomfort. Patients with dysautonomia showed significant longer periods of coma (24.78 vs. 7.99 days) and mechanical ventilation (22.67 vs. 7.21 days). Dysautonomia was associated with diffuse axonal injury (DAI) [relative risk (RR) 20.83, CI 4.92–83.33] and the development of spasticity (RR 16.94, CI 3.96–71.42). Patients with dysautonomia experienced more secondary complications. They tended to have poorer outcome. Conclusions: Dysautonomia occurs in approximately 10% of patients surviving severe TBI and is associated with DAI and the development of spasticity at follow‐up. The initiation of dysautonomia by discomfort supports the Excitatory: Inhibitory Ratio model as pathophysiological mechanism.     

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。     

Is β-APP a marker of axonal damage in short-surviving head injury?

β-Amyloid precursor protein (β-APP), a normal constituent of neurons which is conveyed by fast axonal transport, has been found to be a useful marker for axonal damage in cases of fatal head injury. Immunocytochemistry for β-APP is a more sensitive technique for identifying axonal injury than conventional silver impregnation. This study was designed to determine how quickly evidenc of axonal damage and bulb formation appears. Using this method a variety of brain areas were studied from 55 patients who died within 24 h of a head injury. Immunocytochemical evidence of axonal injury was first detected after 2 h survival, axonal bulbs were first identified after 3 h survival, and the amount of axonal damage and axonal bulb formation increased the longer the survival time. Received: 8 February 1996 / Revised, accepted: 13 May 1996     

Neuropathological investigation of cerebral white matter lesions caused by closed head injury

In order to ascertain whether there is widespread axonal disruption of cerebral white matter in the so‐called ‘diffuse axonal injury’ (DAI), a type of closed head injury, proposed by Adams et al. the author investigated his own cases clinicopathologically. Twenty‐six male autopsied cases of head injury, aged between 19 and 84, 15 of which had sustained road traffic accidents, were examined; the others were due to falling from heights and so on. The study group all belonged to non‐missile head injuries and included 12 cases of diffuse brain injury, as well as 14 cases of focal brain injury, according to the classification of Gennarelli et al. The survival time ranged from 2 h to 21 years. Formalin‐fixed brains were cut coronally so as to make paraffin‐embedded hemispheric sections. Then these sections were stained conventionally (HE, Bodian, Kluver‐Barrera and Holzer) and immunohistochemically (GFAP) to assess axonal decrease, myelin pallor and gliosis by the use of light microscopy. In the 13 chronic cases that died more than 1 month after the accidents, the intensities of gliosis, myelin pallor and axonal decrease tended to correlate with each other. In the 13 acute cases who died less than 1 month after their accident, the degree of axonal decrease in white matter seemed to correlate with the severity of myelin pallor. Regardless of types of trauma, however, axonal retraction balls, the so‐called hallmark of DAI, were found only with myelin pallor suggesting the presence of brain swelling after the injury. Therefore these findings indicate that it may be difficult to accept the notion of DAI, that is, the presence of axonal retraction balls without brain swelling. In addition, diffuse vascular injury (2 cases) as well as rarefaction of subcortical white matter (6 cases) were presented and their pathogenesis individually discussed based on a literature review.     

弥漫性轴索损伤脑脊液神经元特异性烯醇化酶的动态变化及意义

目的 探讨弥漫性轴索损伤(DAI)病人脑脊液神经元特异性烯醇化酶(NSE)的动态变化及其临床意义.方法 分别用放射免疫测定法检测76例DAI病人(实验组)和15例无神经系统疾病者(对照组)的脑脊液NSE含量.实验组根据入院时GCS评分分为轻型组23例、中型组27例和重型组26例.分别于颅脑损伤后12h、1d、3d、7d、14d采集脑脊液标本,分析NSE水平与颅脑损伤严重程度及预后的关系.结果 与对照组比较,轻型组伤后12 h～3 d、中型组伤后12h～7d、重型组伤后12 h～14 d的NSE水平均明显增高(P＜0.05);重型组各时间点NSE水平明显高于轻型组和中型组(P＜0.01).随访3个月,轻型组、中型组和重型组预后不良率分别为0％、14.81％及73.08％.结论 脑脊液NSE水平可作为判断DAI损伤程度及预后的指标,并指导选择和调整治疗措施.     

Sodium channelopathy induced by mild axonal trauma worsens outcome after a repeat injury

There is great concern that one mild traumatic brain injury (mTBI) predisposes individuals to an exacerbated response with a subsequent mTBI. Although no mechanism has been identified, mounting evidence suggests traumatic axonal injury (TAI) plays a role in this process. By using a cell culture system, a threshold of mild TAI was found where dynamic stretch of cortical axons at strains lower than 5% induced no overt pathological changes. However, the axons were found to display an increased expression of sodium channels (NaChs) by 24 hr. After a second, identical mild injury, pathologic increases in [Ca²⁺]_i were observed, leading to axon degeneration. The central role of NaChs in this response was demonstrated by blocking NaChs with tetrodotoxin prior to the second injury, which completely abolished postinjury increases in [Ca²⁺]_i. These data suggest that mild TAI induces a form of sodium channelopathy on axons that greatly exaggerates the pathophysiologic response to subsequent mild injuries. © 2009 Wiley‐Liss, Inc.     

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...     

The role of abnormalities in the corpus callosum in social cognition deficits after Traumatic Brain Injury

The corpus callosum (CC) is vulnerable to severe traumatic brain injury (TBI). Social cognition requires integration of non-verbal and verbal information in order to understand social behaviour and may be compromised if the CC is damaged. 17 adults with severe, chronic TBI and 17 control participants underwent structural MRI and Diffusion Tensor Imaging. A region of interest analysis examined fractional anisotropy (FA) and mean diffusivity (MD) across regions of the CC. Performance on The Awareness of Social Inference Test (TASIT): part 1 (emotion recognition) and parts 2 and 3 (social inference), was examined in relation to FA and MD. Across participants, higher genu FA values were related to higher TASIT part 3 scores. Increased splenium FA was associated with better performance for TASIT parts 1–3. There was no association between DTI values and TASIT in the controls alone. In the TBI group, FA of the genu and splenium was correlated with TASIT part 3. The pattern of performance was similar when controlling for non-social cognitive ability. In conclusion, social information is complex and multi-modal requiring inter-hemispheric connection. People with TBI, regardless of focal grey matter injury, may lose social cognitive ability due to trauma related changes to the corpus callosum.     

大鼠弥漫性轴索损伤后MBP及β-app封闭蛋白FE65表达的变化

目的：研究弥漫性轴索损伤(diffuse axonal injury DAI)后MBP及β-app封闭蛋白FE65表达的变化,为DAI的早期诊断提供临床资料。方法：应用ELISA法研究DAI后MBP的变化及应用实时RT-PCR方法研究FE65mRNA的表达变化。近交成年雌性SD大鼠48只,随机分为两组,每组24只,4只为对照。制备DAI模型,在伤后0．5h、1h、6h、12h、24h几个时间点,取4只动物处死取材用于实验。结果：大鼠DAI损伤后12h MBP表达开始增加,24h时表达更明显(P<0．05),而对照组FE65mRNA的表达在损伤后0．5h即开始升高,至1h达到高峰,随后逐渐下降。结论：MBP在DAI后12h表达开始增加;FE65在伤后30min内表达即升高,1h时达到高峰。FE65是DAI诊断的一种特异性指标,Real-timePCR是诊断DAI的一种快速、敏感的方法,尤其适于早期检测极少量的RT-PCR产物。     

Diagnostic approaches to predict persistent post-traumatic symptoms after mild traumatic brain injury – a literature review

Mild traumatic brain injury (mTBI) is one of the most frequently diagnosed neurological disorders in emergency departments. Although there are established recommendations for the diagnosis and treatment in the acute stage, there is an on-going debate in which diagnostic methods and risk factors predict unfavourable long-term outcome after mTBI. This literature review addresses the question, which diagnostic approaches may best predict persistent post-traumatic symptoms (pPTS). A literature search for experimental studies from January 2000 to September 2014 evaluating the following diagnostic approaches (1) susceptibility weighted imaging (SWI), (2) diffusion tensor imaging (DTI), (3) magnetic resonance spectroscopy (MRS), (4) functional magnetic resonance imaging (fMRI), as predictive factors of pPTS or unfavourable cognitive outcome in adult populations with mTBI was performed. DTI has been proved to be a valuable tool to identify diffuse axonal injury (DAI) after mTBI. Additionally, some studies showed associations between DAI and unfavourable cognitive outcome. SWI has shown to be a highly sensitive imaging method to identify microbleeds. The presence and quantity of microbleeds in this imaging technique can further provide aetiological evidence for pPTS. MRS provides information about local neurons metabolism and preliminary data show that creatine–phosphocreatine levels measured after mTBI are predictive of cognitive outcome and emotional distress. The results of one study have shown fMRI as a useful tool to differentiate mTBI patients with pPTS from controls and mTBI patients without pPTS in a resting-state condition. From the evaluated diagnostic approaches to predict pPTS after mTBI, DTI, SWI, MRS, and fMRI seem to have adequate sensitivity and specificity as predictive diagnostic tools for pPTS. Large longitudinal clinical trials are warranted to validate the prognostic applicability and practicability in daily clinical practice.     

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.     

Concentration of brain free magnesium following severe brain injury correlates with neurologic motor outcome

Recent studies have shown that brain intracellular free magnesium concentration significantly declines following mild to severe, focal and diffuse traumatic brain injury. However, little is known about how this decline or its attenuation by magnesium salts relates to neurologic outcome. This study uses phosphorus magnetic resonance spectroscopy and rotarod tests to characterise the relationship between brain free magnesium concentration and neurologic motor scores following severe, diffuse traumatic brain injury in rats. An intravenous bolus of MgSO(4) or MgCl(2) (100 mumoles/kg) at 30 min following brain injury significantly attenuated the postinjury brain free magnesium decline. This improved magnesium homeostasis was sustained for the entire postinjury monitoring period (1 week). There was an associated significant improvement in neurologic motor function in magnesium treated rats. Moreover, the brain free magnesium concentration over the one week period was linearly correlated with the neurologic motor function (r=0.70; P < 0.001) as assessed on a daily basis. We propose that brain free magnesium concentration may be used as a prognostic indicator of neurologic motor function after traumatic brain injury.