Dose-dependent neuronal injury after traumatic brain injury

The Fluoro-Jade (FJ) stain reliably identifies degenerating neurons after multiple mechanisms of brain injury. We modified the FJ staining protocol to quickly stain frozen hippocampal rat brain sections and to permit systematic counts of stained, injured neurons at 4 and 24 h after mild, moderate or severe fluid percussion traumatic brain injury (TBI). In adjacent sections, laser capture microdissection was used to collect uninjured (FJ negative) CA3 hippocampal neurons to assess the effect of injury severity on mRNA levels of selected genes. Rats were anesthetized, intubated, mechanically ventilated and randomized to sham, mild (1.2 atm), moderate (2.0 atm) or severe (2.3 atm) TBI. Four or 24 h post-TBI, ten frozen sections (10 microm thick, every 15th section) were collected from the hippocampus of each rat, stained with FJ and counterstained with cresyl violet. Fluoro-Jade-positive neurons were counted in hippocampal subfields CA1, CA3 and the dentate gyrus/dentate hilus. At both 4 and 24 h post-TBI, numbers of FJ-positive neurons in all hippocampal regions increased dose-dependently in mildly and moderately injured rats but were not significantly more numerous after severe injury. Although analysis of variance demonstrated no overall difference in expression of mRNA levels for heat shock protein 70, bcl-2, caspase 3, caspase 9 and interleukin-1beta in uninjured CA3 neurons at all injury levels, post hoc analysis suggested that TBI induces increases in neuroprotective gene expression that offset concomitant increases in deleterious gene expression.     

Head injury

Obliteration of mesencephalic cisterns, midline shift, subdural and epidural hematomas, shearing injuries involving the brainstem and/or interpeduncular cistern, fractures of the sphenoid body and/or clivus, as well as perfusion defects larger than the intracerebral hematoma have been identified in the recent literature as findings indicative of poor outcome in patients with head injury.     

Craniocerebral injury promotes the repair of peripheral nerve injury

The increase in neurotrophic factors after craniocerebral injury has been shown to promote fracture healing. Moreover, neurotrophic factors play a key role in the regeneration and repair of peripheral nerve. However, whether craniocerebral injury alters the repair of peripheral nerve injuries remains poorly understood. Rat injury models were established by transecting the left sciatic nerve and using a free-fall device to induce craniocerebral injury. Compared with sciatic nerve injury alone after 6–12 weeks, rats with combined sciatic and craniocerebral injuries showed decreased sciatic functional index, increased recovery of gastrocnemius muscle wet weight, recovery of sciatic nerve ganglia and corresponding spinal cord segment neuron morphologies, and increased numbers of horseradish peroxidase-labeled cells. These results indicate that craniocerebral injury promotes the repair of peripheral nerve injury.     

Ruxolitinib attenuates secondary injury after traumatic spinal cord injury

Excessive inflammation post-traumatic spinal cord injury(SCI)induces microglial activation,which leads to prolonged neurological dysfunction.However,the mechanism underlying microglial activation-induced neuroinflammation remains poorly understood.Ruxolitinib(RUX),a selective inhibitor of JAK1/2,was recently reported to inhibit inflammatory storms caused by SARS-CoV-2 in the lung.However,its role in disrupting inflammation post-SCI has not been confirmed.In this study,microglia were treated with RUX for 24 hours and then activated with interferon-γfor 6 hours.The results showed that interferon-γ-induced phosphorylation of JAK and STAT in microglia was inhibited,and the mRNA expression levels of pro-inflammatory cytokines tumor necrosis factor-α,interleukin-1β,interleukin-6,and cell proliferation marker Ki67 were reduced.In further in vivo experiments,a mouse model of spinal cord injury was treated intragastrically with RUX for 3 successive days,and the findings suggest that RUX can inhibit microglial proliferation by inhibiting the interferon-γ/JAK/STAT pathway.Moreover,microglia treated with RUX centripetally migrated toward injured foci,remaining limited and compacted within the glial scar,which resulted in axon preservation and less demyelination.Moreover,the protein expression levels of tumor necrosis factor-α,interleukin-1β,and interleukin-6 were reduced.The neuromotor function of SCI mice also recovered.These findings suggest that RUX can inhibit neuroinflammation through inhibiting the interferon-γ/JAK/STAT pathway,thereby reducing secondary injury after SCI and producing neuroprotective effects.     

Closed head injury

Abstract

H. S. Levin, A. L. Benton and R. G. Grossman. Neurobehavioral Consequences Of Closed Head Injury. New York, Oxford University Press, 1982, 279 Pp. Isbn     

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.     

Spinal cord injury

The evaluation and treatment of spinal cord injury continues to evolve, enhanced by new imaging modalities. Their application in reference to the cervical, thoracic, and lumbar spine is discussed. Treatment options, both conservative and surgical, are outlined.     

Hypoglycemic brain injury

Summary Profound hypoglycemia causing the disappearance of spontaneous EEG activity was induced by insulin in rats. For analysis of cerebral cortical concentrations of labile phosphates, glycolytic metabolites and amino acids, the brain was frozen in situ. For microscopic analysis of the corresponding cerebral cortical areas the brain was fixed by perfusion. Hypoglycemia with an isoelectric EEG for 30 and 60 min caused severe perturbation of the cerebral energy metabolites. After both 30 and 60 min of isoelectric EEG, two microscopically different types of nerve cell injury were seen. Type I injury was characterized by angulated, darkly stained neurons with perineuronal vacuolation, mainly affecting small neurons in cortical layer 3. Type II injured neurons, mainly larger ones in layers 5–6, were slightly swollen with vacuolation or clearing (depending on the histotechnique used) of the peripheral cytoplasm, but had no nuclear changes.Recovery was induced by glucose injection. Improvement in the cerebral energy state occurred during the 30 min recovery period even after 60 min of hypoglycemia. However, the persisting reduction in the size of adenine nucleotide and amino acid pools after 30 or 180 min recovery suggested that some cells remained damaged. In confirmation many type I injured neurons persisted during the recovery suggesting an irreversible injury. The disappearance of virtually all type II injuries indicated reversibility of these histopathological changes.The microscopic changes in hypoglycemia were different from those in anoxia-ischemia suggesting a dissimilar pathogenesis in these states despite the common final pathway of energy failure.     

Assessment of closed head injury in trauma-related spinal cord injury

The complete medical records of 122 patients who sustained traumatic spinal cord injuries were reviewed to determine the frequency and results of emergency room assessments for loss of consciousness (LOC) and post-traumatic amnesia (PTA). Eighty-eight percent of the patients were assessed for LOC and 19% were assessed for PTA. Fifty patients (41% of the total population) admitted to LOC, PTA or both. Fourteen of these 50 patients underwent subsequent radiographic examinations of the skull, all of which were negative. Because of the association of intracranial complications and long-term cognitive sequelae with even brief LOC or PTA, early recognition of craniocerebral trauma is an important component of the acute management of spinal cord injured patients.     

Traumatic brain injury

Abstract

Traumatic brain injury (TBI) is one of the leading causes of death and disability world wide. In the United States alone, nearly 1·7 million individuals are treated in the hospital setting for TBI of all severities, which accounts for over US$48 billion of health care cost annually. This special issue of Neurological Research provides a broad coverage of several important topics in TBI, including contemporary imaging of mild TBI, management of chronic subdural hematoma (cSDH), use of vagus nerve stimulation (VNS) to treat TBI, reviews on blast TBI and chronic traumatic encephalopathy (CTE), as well as basic science studies in different rodent models of TBI. The authors aim to provide some insight on TBI to neurosurgeons, neurologists, rehabilitation doctors, and other specialists treating TBI patients as well as neuroscientists who are involved in neurotrauma research.     

Brain retraction injury

This paper reviews the literature of the brain retraction injury during the last century. The review focused on the instrument characteristic as well as the physiopathological and histopathological damage of the brain induced by brain retraction. It was found that lesions were induced by cerebral ischemia. We conclude that a better monitoring system needs to be developed to avoid brain injury.