Effects of Head Orientation on the Intracranial Pressure of Rats Exposed to Shock Waves

With the increasing number of military personnel returning from conflicts with neurological manifestations of traumatic brain injury (TBI), there has been a great focus on the effects resulting from blast exposure (Okie 2005; Hicks et al. 2010). Recently, experimental studies have been reported which investigated the biomechanical response of the rat head exposed to a shock wave. The results indicated that the imparted shock wave may induce multiple response modes of the skull, including global flexure, which may have a significant contribution to the mechanism of injury (Bolander et al. 2011; Dal Cengio Leonardi et al. 2011). However, the question of whether head orientation could play a role in the level of energy imparted on the brain is still of concern. This study quantitatively measured the effect of head orientation on intracranial pressure (ICP) of rats exposed to a shock wave. Furthermore, the study examined how skull maturity affects ICP response at various orientations. It was hypothesized firstly that skull flexural modes dominate the ICP response, hence varying head orientation would be expected to alter this imparted stress waveform. The head orientation affects not only the shape and size of the “presented area” exposed to the incident wave, but the degree and nature of the response of the individual skull plate elements due to the variance of skull physiology. As such, this has a significant influence on the stress that the shock wave imparts on the brain due to changes in skull dynamics.