According to the different ways of external violence on the head, divided into two kinds of direct violence and indirect violence. 1, direct violence by external forces acting directly on the head, resulting in cranio-cerebral injury. Commonly there are the following three cases: ① accelerated injury: refers to the head at rest by the impact of moving objects, the direction of external force, resulting in cranial injury. This injury can cause damage to the scalp, skull and brain tissue at the point of impact, called impact point injury; in addition, it can also cause brain tissue damage on the opposite side of the point of impact, called hedonic injury. ② deceleration injury: the movement of the head hit a stationary object and suddenly stop movement, resulting in cranio-cerebral injury. At this time can also produce impact point and hedonic injury. ③ two or more different directions of external force, while acting on the head, the head due to extrusion deformation caused by cranial injury. This injury only impact point injury, and does not appear hedonic injury. 2, indirect violence The external force acting on other parts of the body, through the transmission of the head, causing cranio-cerebral injury. Commonly there are three cases: ① external force acting on the foot or hip, through the spine to the head, causing cranio-cerebral injury, violence indirectly hit the base of the skull, local fractures or brain damage, while the head movement is suddenly blocked and can produce hedonic injury. ② External force acting on the chest, so that the sudden increase in internal pressure in the chest, impact on the superior vena cava, through the blood will be transmitted to the intracranial and external vessels can cause intracranial and external extensive punctate hemorrhage. External force acting on the torso can cause sudden acceleration or deceleration of the torso. Due to inertia, the movement of the head often lags behind the torso, which can cause overextension or hyperflexion of the head junction, or overextension followed by jumping back and hyperflexion. This can not only cause injury to the ligaments, joints, bone and spinal cord at the craniocervical junction, but can also cause brain injury by rotational movement of the brain within the skull. The injuries seen clinically are often complex, as the above-mentioned violent factors can occur in the same accident, and the scalp, skull, and brain tissue can be involved separately or simultaneously, and the degree of damage to different tissues is not uniform. However, brain injury is often a determinant of prognosis, and the severity of skull fracture and scalp injury is often used as a reference indicator to estimate the presence and severity of brain injury.