A NEW EXPERIMENTAL-MODEL OF CONTUSION IN THE RAT - HISTOPATHOLOGICAL ANALYSIS AND TEMPORAL PATTERNS OF CEREBRAL BLOOD-FLOW DISTURBANCES

The authors have derived a simple reproducible rodent of focal injury that uses a mechanical suction force applied through intact dura. The time course and pattern of changes in neurons, glia, and microvasculat ure were investigated using this model. Early traumatic disruption of the blood-brain barrier and hemorrhage do not occur in this model; how ever, many of the features of human contusion seen with light and elec tron microscopy are closely reproduced. At the site of injury, early s welling adn lucency of neural dendritic processes have been shown to p recede an astrocyte response. In the absence of perivascular hemorrhag e, delayed perivascular protein leakage and polymorphonuclear infiltra tion of the damaged cortex occurs, which is suggestive of an acute inf lammatory response. Cerebral blood flow (CBF) has been measured using C-14-iodoantipyrine autoradiography at 30 minutes, 4 hours, and 24 hou rs after induction of negative-pressure injury in rats anesthetized wi th halothane and in time-matched sham-operated controls. A significant reduction in blood flow in the sensorimotor cortex at the site of the injury was present at 30 minutes, 4 hours, and 24 hours after inducti on of the lesion, compared to the contralateral cortex (superficial la mina, ipsilateral 50 +/- 7 ml/100 g/minute, contralateral 112 +/- 26 m l/100 g/minute). The CBF was significantly reduced at the ipsilateral entorhinal cortex at 30 minutes postinjury but no significant reductio n was demonstrated at later time points. Although marked alternations in CBF occurred in this cortical injury model, the magnitude and durat ion of the reduction in CBF are not consistent with those necessary fo r production of ischemic cell damage. These data indicate that this mo del of cortical injury can be used to examine biomechanical aspects of confusion without domination by ischemic pathophysiology.