Prognosis
The highest-velocity injuries tend to have the worst associated damage. Penetrating injury from any missile such as a bullet has a mortality rate of 92%. Thus, firearms cause the most head injury-related deaths. Perforating injuries have an even worse prognosis.
Penetrating head trauma can cause impairment or loss of abilities controlled by parts of the brain that are damaged. A famous example is Phineas Gage, whose personality appears to have changed (though not as dramatically as usually described) after a penetrating injury to his frontal lobe(s).
People with subarachnoid hemorrhage, a blown pupil, respiratory distress, hypotension, or cerebral vasospasm are more likely to have worse outcomes.
People with penetrating head trauma may have complications such as acute respiratory distress syndrome, disseminated intravascular coagulation, and neurogenic pulmonary edema. Up to 50% of patients with penetrating brain injuries get late-onset post-traumatic epilepsy.
Read more about this topic: Penetrating Head Injury