Experimental Studies On The Brain Diffuse Axonal Injury(DAI) Due To Instant Lateral Head Rotation

Brain diffuse axonal injury (DAI) is associated with high morbidity and mortality, its clinical treatment is very difficult. The present study with SD rats as objects, produced the animal model of brain DAI by instant lateral head rotation,. explored deeply the mechanism of DAI and proposed the possible therapeutic strategies.I ) A head rotation injury device was worked out and made that could move the head of a 0.21kg rat instantly in the coronal plane by 90° to the right with the rotation time of the rat head 2ms, the angular volecity 801.27 rad/s and the angular acceleration 2.044×10~5 rad/s~2. A relational formula was set up between the rotation time , the angular volecity or the angular acceleration and the rat body weight. According to the formula, the head of a rat weighing below 0.3kg could be rotated coronally by 90° in less than 2.09ms while its angular volecity and angular acceleration were beyond 753.13rad/s and 1.806×10~5 rad/s~2 respectively. The latter two were much higher than the DAI thresholds of augular volecity and angular acceleration proposed by Margulies(1992). All rats manifested some abnormalities of brainstem functions such as conscious disturbance and respiratory rhythm disorder immediately after their head was rotated. Early mortality of injured rats amounted to 17%. At 6~24h post injury many sites within the brain(especially the brainstem) were seen under light miaoscope to have diffuse axonal swelling, axonal disconnection and axonal retraction balls associated with hemorrhagic spots and extravascular edema. At 3~6d, gliosis was present. The above pathological changes accorded with those of DAI. It was suggested that our injury device produced an ideal DAI model of rats by instantly rotating their head laterally. So far, no model of rat DAI by head rotation has been reported abroad.II) In this model, mainly injured were the longitudinal neuronal axons of thebrainstem and the most severely damaged was the lower part of the brainstem. Itreflected the midline distribution effects of shearing force formed within the brain underthe rotating acceleration-deceleration motion. It was verified that the effect of shearingforce was the biomechanical reason for DAI.