Pathophysiology

Though it is more likely to cause infection, penetrating trauma is similar to closed head injury such as cerebral contusion or intracranial hemorrhage in a number of ways. 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).[2] Studies with PET scanning and transcranial Doppler imaging have shown that changes in cerebral blood flow, such as hypoperfusion and vasospasm, can follow penetrating head injury.[4] These changes can last for two weeks.[4] An ischemic cascade similar to the course of cellular and metabolic events that follow other head injuries may follow penetrating head injuries.[4] Sometimes in penetrating injuries, the brain releases thromboplastin, which can lead to problems with blood clotting.[5] While blunt head trauma does not present a risk of shock due to hemorrhage, penetrating head trauma does.