Penetrating head injury

, a railroad worker who had a tamping iron driven through his skull in an 1848 accident. In penetrating injury from high-velocity missiles, injuries may occur not only from initial laceration and crushing of brain tissue by the projectile, but also from the subsequent cavitation. High-velocity objects create rotations and can create a shock wave that cause stretch injuries, forming a cavity that is three to four times greater in diameter than the missile itself. ==Pathophysiology==

Though it is more likely to cause infection, penetrating trauma is similar to closed head injury such as cerebral contusion or intracranial hemorrhage. As in closed head injury, intracranial pressure is likely to increase due to swelling or bleeding, potentially crushing delicate brain tissue. Most deaths from penetrating trauma are caused by damage to blood vessels, which can lead to intracranial hematomas and ischemia, which can in turn lead to a biochemical cascade called the ischemic cascade. The injury in penetrating brain trauma is mostly focal (that is, it affects a specific area of tissue). While blunt trauma to the head does not present a risk of shock due to hemorrhage, penetrating head trauma does. ==Diagnosis and treatment==

A person with a penetrating head injury may be evaluated using X-ray, CT scan, or MRI (MRI can only be used when the penetrating object would not be magnetic, because MRI uses magnetism and could move the object, causing further injury). Surgery may be required to debride or repair the injury or to relieve excessive intracranial pressure. Intracranial pressure is monitored and attempts are made to maintain it within normal ranges. Intravenous fluids are given and efforts are taken to maintain high blood oxygen levels. ==Prognosis==

The highest-velocity injuries tend to have the worst associated damage. A study published in 1991, which documented 314 individuals who had had penetrating cranial injuries caused by gunshot wounds, found that 73% died from their injuries at the scene of the incident, and a further 19% ultimately died later, thus indicating a total mortality rate of 92%. Up to 50% of patients with penetrating brain injuries get late-onset post-traumatic epilepsy. ==See also==