An Evaluation of Decompression in Experimental Head Injury

HE therapy for acute brain swelling continues to be unsatisfactory in severe cases. Associated cerebral laceration and contusion account for much of the deficit noted, but there can be little doubt that the swelling which occurs can augment the degree of injury, and may possibly change a reversible lesion into an irreversible one. It is important to recognize that acute brain swelling has been shown to represent primarily an increase in the intravascular component of the intracranial volume, that is, it is a sudden distention of the vascular bedY ,4 Later subacute brain swelling, or cerebral edema, may develop. This represents primarily an increase in the extravascular component of the intracranial volume, whether intra- or extracellular. This paper is primarily concerned with the reduction of morbidity and mortality in the acute swelling phase. We should recognize, however, that by reducing morbidity in the acute phase we may be ameliorating some of the factors that set the stage for the later development of subacute swelling. One of the problems in assessing the various possible therapeutic methods in head injury is the establishment of an adequate model. If the model is a free head which is given a sudden, violent blow, the types and degree of injury cannot be well controlled. There may be varying degrees of superimposed brain laceration and contusion, as well as the added problems of acceleration, deceleration, and hemorrhage. Thus, the mortality and morbidity of such a model would include many more factors than swelling alone, and the results would be unpredictable. We have chosen extradural compression by a balloon because the method is simple, because the duration and intensity of the injury can be well controlled, and because a repeatable end point may be obtained. In