Narrow Results

This paper presents a new analysis of the physics of closed head injury caused by intense acceleration of the head. At rest a 1 cm gap filled with cerebrospinal fluid (CSF) separates the adult human brain from the skull. During impact, whole head acceleration induces artificial gravity within the skull. Because its density differs slightly from that of CSF, the brain accelerates, strikes the inner aspect of the rigid skull, and undergoes viscoelastic deformation. Analytical methods for a lumped parameter model of the brain predict internal brain motions that correlate well with published high-speed photographic studies. The same methods predict a truncated hyperbolic strength-duration curve for impacts that produce a given critical compressive strain. A family of such curves exists for different critical strains. Each truncated hyperbolic curve defines a head injury criterion (HIC) or threshold for injury, which is little changed by small offsetting corrections for curvature of the brain and for viscous damping. Such curves predict results of experimental studies of closed head injury, known limits for safe versus dangerous falls, and the relative resistance of smaller versus larger animals to acceleration of the head. The underlying theory provides improved understanding of closed head injury and better guidance to designers of protective equipment and to those extrapolating research results from animals to man.

Blast-induced traumatic brain injury (bTBI) has become a signature injury in recent military conflicts and terrorist attacks. However, the mechanisms and thresholds for such injury are still unknown. In this paper, effort has been made toward establishing the threshold due to primary blast based on the published injury data in the rat. Peak incident overpressure and pulse duration of the incident wave were used as predictors and the injury risk curves for the rat were derived via a linear logistic regression analysis. A scaling law based on body mass was then used to scale the tolerance curves from the rat to the pig and the human. The injury risk curve for bTBI was compared with that for the lung. The results reveal different injury mechanisms between these two organs. The developed injury curves can be used in the design of personal protective equipment against primary bTBI.