A Histopathological and Immunohistochemical Study of Traumatic Diffuse Axonal Injury in Albino Rats
Kamal Salih M Sayim, Magdy M. Ashmawy
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Diffuse axonal injury (DAI) is a frequent result of traumatic deceleration injuries and a frequent cause of persistent vegetative state in patients. DAI is the most significant cause of morbidity in patients with traumatic brain injuries, which most commonly are the result of high-speed motor vehicle accidents. Axonal injury (AI) has been described as a phenomenon which can be induced as a diffuse change, i.e. diffuse axonal injury (DAI) caused by traumatic brain injury. It is only when obvious lesions are absent or minimal; the occult effect of DAI can be invoked. The aim of this study is to evaluate the vitality of the brain and approximately the survival time of rats subjected to sublethal head trauma, using some ordinary and immunohistochemical stains for the injured brains. Sixty adult male albino rats were used in this study, 8 of them were kept as a control group and the others were subjected to sublethal head trauma under light ether anaesthesia. Then they were grouped after exclusion of cases with skull fracture or intracranial hemorrhage, according to their survival time into 4 groups: group I (0—. <30 minutes), group II (0.5 hour—. <2 hours), group III (2 hours—. <4 hours) and group IV (4 hours—. < 6 hours). Sections from different brain areas were prepared with different stains and examined. Gross examination revealed peticheal hemorrhages scattered in all brains, especially brain stem compared to the control group. Microscopic examination pointed to the possibility of detecting the neuronal injury as early as 0.5-2 hours using immunoreactivity against neurone specific enolase (NSE). Also B-amyloid precursor Protein (B-APP) immunoreaction could detect the axonal injury as early as 2-4 hours. Silver stain and H & E stains could reveal these neuronal traumatic changes at later times (4-6 hours). So, immunohistochemical stains are useful to detect neuronal changes for short survivors while ordinary stains are suitable to detect neuronaj changes for victims surviving longer times after trauma. It is to be noted that the diffuse nature of these neuronal injuries is necessary for the diagnosis of traumatic head injury, since ischemic hypoxic insults can lead to localized neuronal changes. So, detection of DAI is helpful in the diagnosis of sudden obscure deaths, especially when occult head trauma is suspected.
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