1) Head injuries can cause primary brain injury at impact or secondary brain injury afterwards from factors like hypoxia or swelling.
2) Head injuries are classified by Glasgow Coma Scale from minor to severe. CT scans are used to identify fractures or bleeds in the brain.
3) Common brain injuries include extradural hematomas requiring urgent surgery, acute subdural hematomas also often needing surgery, and cerebral contusions monitored for swelling.