Differential Tolerance of Frontal and Temporal Lobes to Contusion Induced by Angular Acceleration

Frontal and temporal lobe contusions that were caused by a single sagittal plane angular acceleration impulse were analyzed. At neuropathological exam the depth, extent, and location of contusions were mapped and described according to a classification previously developed for human use. Of 30 rhesus monkeys subjected to a single angular acceleration impulse, 13 had no frontal or temporal contusion (Group 1), 8 had only frontal contusion (Group 2) and 9 had temporal contusions (Group 3). Correlation with angular acceleration, tangential acceleration and tangential force showed that the three groups were statistically different. The mean peak positive tangential force for Groups 1-3 was 541, 659 and 766 newtons respectively (p<0.10). This suggested that as mechanical imput increased, frontal contusions occur before temporal contusions and that the threshold for frontal contusion is less than that for temporal contusion. If this relationship is true, one would predict that if there is sufficient input to cause a temporal contusion then a frontal contusion should also be present. In fact, in Group 3, 8 of the 9 animals with temporal contusion also had frontal contusion. Thus only once did a temporal contusion occur in the absence of frontal contusion. Furthermore, the frontal contusions in Group 3 were statistically more extensive than either the frontal contusion of Group 2 or than the temporal contusions of Group 3. These data support the concept that in angular acceleration the threshold for frontal contusions is less than the threshold for temporal contusions. The resons why this is so could be related either to differences in the mechanical properties of the tissues or to regional differences of the mechanical input. Since the authors feel that the data best support the hypothesis that these contusions result from deceleration contact forces, we favor the latter explanation.