1975 Volume 15pt1 Issue 1 Pages 57-65
The present experiment was undertaken to clarify the pathogenesis of primary fatal head injury due to impact and further to obtain a severity index denoting the relationship between the magnitude of impact and the severity of head injury in animals with experimental blunt head injuries caused by simplified impact upon the cranium.
The experiment was conducted on Ketalar-anesthesized rhesus monkeys. Impact was imparted to the animals by means of a 12 in. HYGE impact tester. Before and after the impact the animals were subjected to a series of examinations at intervals, including respiration, ECG, blood pressure, cerebral circulation, partial pressure of blood gases, acid-base equilibrium and EEG. Pathological examination, measurements of lactic acid and monoamine contents in various portions of the brain were also made.
An impact upon the head, at an acceleration in the horizontal antero-posterior direction of 1000-1500 G and a duration of 3-4 msec, proved fatal invariably in animals weighing more than 8 kg (body weight×effective acceleration above 30 kg). In dead animals, primary injury consisting of narrowing of lumen and stoppage of blood flow in perforating arteries of the brain-stem and small hemorrhages in the same areas was noted. It was demonstrated that these changes give rise to central dysregulation of the circulatory (including heart) and respiratory systems which in turn acts on cerebral circulation and metabolism.
This fact not only proves the existence of a primary fatal head injury and further clarifies its mechanism of development but also suggests the possibility of grading the severity of head injury by simplified impact and also by expressing the relationship between the magnitude of impact and the severity of brain damage as a severity index.
