EXPERIMENTAL BRAIN DAMAGE FROM FLUID PRESSURES DUE TO IMPACT ACCELERATION. 1. Design of Experimental Procedure

Abstract

The significance of the intracranial acceleration prcssure pattern at impact to the intact skull in production of brain damage is discussed particularly as regards the contre-coup pressures. Sudden pressure changes within the cranial cavity of the rabbit were studied by means of a new impact acceleration model. The rabbit skull was connected with a cylinder. Impact acceleration was applied to the model with the skull contents serving as a "contre-coup end". Skull deformation was minimized by reinforcement of the skull vault. Acceleration, velocity and displacement of the system were recorded at various sites and could be predicted within wide ranges. Simultaneous recordings were also made of the pressure changes in the skull cavity and cylinder contents. By adjusting the acceleration course and by introducing a quantified air bubble (50, 100, 150 mm3) at the impact of the cylinder, it was possible to produce and vary an intracranial pressure pattern of "contre-coup type", including predietahle subatmospheric transients. The mechanics of the intracranial pressure changes and displacements are discussed. The method sccms to be suitable for studying the relations between brief negative-positive pressure variations (about 5 ms) of "contre-coup type" and pathological alterations similar to those reported in other head injury models and in human head trauma.

Mechanisms of brain impact injuries and their prediction: A review

“…Suh et al (1972) found that when impacting a fluid-filled spherical shell, negative pressure regions were not located at the contrecoup site. Other researchers found that negative pressure did not contribute to injury when impacting animal models such as rabbits and Macaques (Stalhammar, 1975a, 1975b; Stalhammar and Olsson, 1975; Nuscholtz et al, 1984). Nuscholtz et al (1984) concluded from their research that cavitation was not a mechanism of injury for contusion, but that head and neck position during impact was of greater importance.…”

Biomechanics of Concussion

“…29 A simple model of the hydrostatic gradients generated within the brain can provide a rudimentary approximation of these pressures and can also predict the effect of pressure-relieving openings (eg, foramen magnum) on the resulting pressure gradients. 30 Experimental measures of the human surrogate response to impact loading also provide key insight into how local impact from a blunt impactor causes a subsequent acceleration of the head and pressure gradient within the cranial contents. Based on these data, the ability to predict, a priori, the pressures generated within the brain under a known external loading condition has improved substantially with the advancement of computationally based finite element models in the past two decades (for recent publications, see Refs.…”

Cavitation in blunt impact traumatic brain injury

“…This problem can be solved by attaching a long column of fluid to a craniotomy and striking the top of the column. This approach created negative pressures and functional deficits in a rabbit model (Stålhammar 1975b , 1975a ; Stålhammar & Olsson 1975 ). Nusholtz et al detected negative pressures with a limiting value consistent with cavitation during head impacts in human cadavers and living primates.…”