Which statement about secondary brain injury is correct?

• A. Signs are often present immediately after an impact to the head.
• B. Hypoxia and hypotension are the two most common causes of secondary brain injury.
• C. Because cerebral edema develops quickly, it is considered to be a primary brain injury.
• D. It results from direct brain trauma following an impact to the head.

Answer: (B)

Secondary brain injury comes from the cascade of events that follow the initial head trauma, meaning the brain damage that occurs after the first impact as the body’s response and the brain’s own processes unfold. The statement that hypoxia (low oxygen) and hypotension (low blood pressure) are the two most common causes fits this idea because when the brain isn’t getting enough oxygen or enough blood flow, it cannot meet its energy demands. This leads to neuronal injury and can worsen the outcome by expanding the initial damage.

Other options don’t capture this sequence. Signs of secondary injury aren’t typically immediate; they often emerge as the cascade progresses over minutes to hours. Cerebral edema is part of the secondary process, not something that defines primary injury—the initial impact is the primary injury, while edema develops afterward and can worsen secondary injury. And secondary injury does not arise from direct brain trauma alone; that direct damage is the primary injury caused by the impact itself.