The mechanism of shaken baby syndrome based on the visualization of intracranial brain motion

Abstract

Shaken Baby Syndrome has been widely recognized as a form of abusive head trauma. On the other hand, short falls are the most common causes given by caregivers in the cases of suspected child abuse. In order for clinicians to distinguish between abusive and accidental head trauma, the difference of the brain injury mechanism between these two situations should be clarified. An anthropometric infant dummy with a novel realistically shaped physical model of an infant head was developed. The three dimensional physical model of an infant head including a transparent skull, deformable brain, cerebrospinal fluid, falx, and tentorium model was reconstructed from the medical images for an infant head, which makes the intracranial brain motion visible. Intracranial brain motions during violent shaking by adult male or low height fall onto a wood floor (h=40, 80, 120 cm) were captured with high speed cameras. From the captured images, relative displacements between skull and cerebrum were measured. Threshold for bridging vein rupture based on the relative displacement of the physical models was defined from a reconstruction of cadaver experiments published by Depreitere et al. From the experimental results in violent shaking cases, the most important mechanism of the brain injuries was the significant change of rotational direction of the head after hyper-flexion or extension, which causes reverse rotational motion between the skull and cerebrum. In the low height fall scenario, the head impact on the surface does not directly cause a relative rotational motion between the skull and cerebrum, but neck flexion after head rebounding causes this. Therefore, the impact angle of the head strongly results in brain injury risk in these events, rather than the fall height. The relative displacements in violent shaking cases, which exceeded the threshold value for bridging vein rupture in most cases, were showed larger than the values in low height fall scenario. Finally, our paper clearly shows the higher subdural hematoma risk in violent shaking events.