Dynamic response and damage estimation of infant head for vibration

Abstract

The most serious head injury resulting from shaken baby syndrome (infant brain injuries resulting from violent shaking attributed to child abuse) is acute subdural hematoma (ASDH). ASDH in infants has a high mortality rate and results in serious permanent injury. However, medical practitioners rely on experience and intuition to determine the cause of infant head injuries because it is difficult to gather accurate evidence from third parties. Therefore, in this study, we have conducted vibration experiment and simulation analysis reproducing the shaking action to provide a scientific basis for the determination of shaken baby syndrome. The finite element model of a six-month-old-infant head is constructed from adult head models and CT scan images of an infant head. The input value is defined as head angle and head displacement obtained from the vibration experiments using a six-month-old-infant dummy. ASDH is caused by the relative rotational motion between the skull and the brain with a rupture of the bridging veins that connect the skull and brain. Accordingly, we have evaluated the relative movement between the skull and brain and measured the stretch ratio of the bridging veins. Then compared this ratio with the threshold, which is the rupture value. As a result, the violent shaking action regarded as shaken baby syndrome abuse ruptures the bridging veins and causes ASHD. As the brain movement follows the skull, the bridging veins are stretched greatly depending on the forced skull movement and the brain's inertia. And the risk of ASDH to occur is high enough to vibrate the infant longer because the stretch ratio increases as time passes in the simulation.