[Recent advances in the study on the mechanism of brain injury]

A cerebral contusion and DAI (diffuse axonal injury) are practically very important in a medico-legal case of the closed head injury. In this paper, we will report the epitome of the recent advances in the study on the mechanism of them. Coup contusion can be mainly attributed to the skull inbending and/or the skull fracture which develop in the impact region. As to the mechanism of the contrecoup contusion, several theories are reported. During rotational movement of the head, intracerebral shear strains would be produced because of brain lag (Holbourn's rotation theory). Anatomical features of the skull plays an important role (Gurdjian). Relative movement between a brain and a skull induces intracranial cavitation due to pressure gradient (Gross's cavitation theory). Brain is injured by deformation pressure induced by skull deformation and acceleration one done by a movement of the head (Lindenberg). The last one is Courville's transmitted waves of force theory. As to DAI, there is Gennarelli's theory. During a rotational movement of a brain caused by high rate of angular acceleration operating for a long period, intracerebral shear strains occur and injure a brain. As to the brain injuries which include a cerebral contusion and DAI, two theories are reported. Centripetal progression of strains to the core of a brain injuries the brain (Ommaya). Natural frequency of impact determines the nature of resulting injury to the brain (Willinger).