Wound Ballistics of Craniocerebral Firearm Injuries

Craniocerebral firearm injuries are associated with high mortality rates as a result of the kinetic energy deposition during the projectile–tissue interaction and its consequences, causing immediate and delayed brain damage. Ballistic factors that contribute to brain injury from bullets are related to the behavior of the projectile (whether it yaws, tumbles, mushrooms or disintegrates following skull penetration) and the creation of bone fragments from the entry site. Pressure waves generated intracranially associated with the temporary cavitation are the hallmark of bullet penetration of the head. Because of the absence of any compensatory mechanism to absorb the transient pressure loading, the largely incompressible brain tissue is subjected directly to its effects. The sudden increase in intracranial pressure and the resultant deformation of the brain during cavitation contributes to the development of brain edema and may affect the cardiac and respiratory centers of the brainstem, even if not transected by the bullet trajectory. Shotgun injuries to the head at close range cause extensive destruction of the brain, usually with catastrophic results, because the pellets enter the cranial cavity bunched together, thus acting as a single projectile of large diameter and kinetic energy. Injuries from fragments present with multiple, more or less circular wounds of various depths, depending on the kinetic energy of the fragments. This review includes a conceptual temporal organization of factors that have a prognostic significance, including those related to projectile and energy transfer characteristics and their consequences.