Diffuse axonal injury due to lateral head rotation in a rat model

Object. The authors investigated the ramifications of producing diffuse axo nal injury (DAI) by lateral head rotation in a rat model. Methods. Using a special injury-producing device, the rat's head was rapidl y rotated 90 degrees in the coronal plane at an angular velocity of at leas t 753.13 rad/second and an angular acceleration of at least 1.806 x 10(5) r ad/second(2); the rotation was complete within 2.09 msec. There were no sta tistically significant changes in PO2, PCO2, pH, or blood pressure values a t 5, 15, or 60 minutes after head rotation compared with their respective p reinjury baseline values. The rats exhibited posttraumatic behavior suppres sion for an average of 12.6 minutes. The mortality rate was 17%. The rats t hat survived had diffuse subarachnoid hemorrhage around the brainstem and u pper cervical cord, but no obvious brain contusion. In sections stained wit h silver or hematoxylin and eosin, axonal swelling and bulblike protrusions at the axonal axis were observed in the medulla oblongata, midbrain, upper cervical cord, and corpus callosum between 6 hours and 144 hours postinjur y. The axonal injuries were most severe in the brainstem and were accompani ed by parenchymal bleeding. The density of bulblike axonal protrusions peak ed 6 hours postinjury in the medulla oblongata and 24 hours postinjury in t he midbrain. Conclusions. Rapid lateral head rotation can produce DAI characterized by s evere damage to the rat brainstem.