Explain the differences between primary and secondary traumatic brain injuries (TBIs)?

Question 1 of 2:

Explain the differences between primary and secondary traumatic brain injuries (TBIs)?

15.A 22-year-old male was an unrestrained front seat passenger of a car traveling at 50 miles per hour. The driver swerved to avoid hitting a deer that darted in front of the car and hit a tree. EMS on the scene noted a stellate fracture of the windshield on the passenger side. The patient was non-responsive at the at the scene when the paramedics arrived, and his pupils were unequal with the left pupil larger and sluggish to react to light. He was placed in a hard-cervical collar per protocol and log rolled onto a long backboard. He was breathing spontaneously at the scene, but pulse oximetry in the EMS unit revealed a SaO₂ of 78% on room air. He was intubated at the scene for airway protection and transported to a Level 1 trauma center. Glasgow Coma Scale=3

After a full trauma work up, the patient was diagnosed with an isolated traumatic brain injury with acute subdural hematoma secondary to coup-contrecoup mechanism of injury. He was emergently taken to the operating room for craniotomy after which he was taken to the Intensive Care Unit (ICU) for close monitoring. He had an intracranial bolt for measurements of his intracranial pressure (ICP).