On the study of brain injury due to rotational impact*

Impacts on the head are commonly identified as the cause of concussive brain injury, which has imposed huge negative health and economic impacts on the world. While brain injury has been recognized as a real issue, researchers are still trying to fully understand how the brain works and how it is injured. Especially, the interactions among the rigid skull, the cerebrospinal fluid (CSF), and the soft brain matter as the head is exposed to a rotational impact, remain unclear. In this study, a lifelike head surrogate, including a soft, artificial brain matter, a transparent, rigid skull, and the CSF in between, has been developed. The slippery motion of the CSF and the motion/deformation of the artificial brain matter were captured using a high-speed camera, as rotational impacts in the sagittal, horizontal, or corona plane were imposed on the head surrogate. The results indicate that the slippery motion of the CSF causes three types of brain injuries: the contusion at the direct impacting region, the diffuse injury widely distributed on the brain surface, and the laceration injury inside the brain. As the first study of its kind, this paper significantly improves the understanding of the fundamental mechanisms involved in the incidence and mitigation of brain injury and provides critical insights into head protection mechanisms.