Pathophysiology, classification and clinical management of TBI
Few morphological studies have been reported on fluid-percussion experimental models using mechanically induced severe brain injury have been reported. This study was initiated to evaluate microscopic and immunohistochemical findings in severe brain injury models using rats. The experimental rats and the methods used were the same as described for a fluid-percussion model. Fluid-percussion models of traumatic brain injury were produce by rapidly injecting fluid volume into the epidural space of the temporal lobe. We used 5 rats which sustained various degrees of injury by high (7.0 atm), medium (5.6 atm) and low (3.5 atm) magnitudes of impact and sham control. The rats were sacrificed and perfused transcardially with buffer solution followed by 2.5% glutaraldehyde at intervals of 24 hours, 3 days, and 7 days, and there were normal and sham control groups. In this immunohistochemical study, monoclonal antibody to 70 kilodalton neurofilament subunit was used in a standard Avidin-Biotin Complex Kit (DAKO). Microscopic findings revealed subarachnoid hemorrhage, lateral IIIrd ventricular hemorrhage, and rarefaction and petechial hemorrhage of the local contusional lesion. In the medium level injury, there was a marked petechial hemorrhage in the corpus callosum and subependymal area. In the high level injury, there was marked edema in the white matter of the ipsi- and contralateral cerebral hemisphere, and multiple petechial hemorrhage in the brain stem and cerebellum. Microscopic findings in the corpus callosum, subependyma and brain stem in the vicinity of petechial hemorrhage revealed a large number of axonal swellings, but in these specimens only a few typical axonal retraction balls were seen with Bodian and immunohistochemical stains. In conclusion, this experimental model seems to simulate local and diffuse shearing injury, showing various morphological characteristics of diffuse axonal injury.