In a traumatic brain injury, which injury occurs on the opposite side of the brain from the impact?

• A. Coup injury
• B. Contrecoup injury
• C. Epidural hematoma
• D. Subarachnoid hemorrhage

Answer: (B)

When the head is struck, the brain’s inertia causes it to keep moving even as the skull stops, so there’s a dual effect: damage at the site of impact (coup injury) and damage on the opposite side as the brain rebounds and hits the inner skull (contrecoup injury). The opposite-side injury is contrecoup because it’s the counterblow the brain receives after initial contact. This pattern is common in acceleration–deceleration injuries, where rapid movement of the brain within the skull leads to bruising or contusion on the far side.

In contrast, an epidural hematoma involves bleeding between the skull and dura often from a skull fracture and arterial injury, which isn’t defined by opposite-side injury. A subarachnoid hemorrhage is bleeding into the space surrounding the brain and can occur for various reasons, not specifically tied to the side opposite the impact.