[1] Penetrating injury can be caused by high-velocity projectiles or objects of lower velocity such as knives, or bone fragments from a skull fracture that are driven into the brain.

Destroyed brain tissue may either be ejected from entrance or exit wounds, or packed up against the sides of the cavity formed by the missile.

[4] 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.

[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.

People with subarachnoid hemorrhage, a blown pupil, respiratory distress, hypotension, or cerebral vasospasm are more likely to have worse outcomes.

[5] People with penetrating head trauma may have complications such as acute respiratory distress syndrome, disseminated intravascular coagulation, and neurogenic pulmonary edema.