Focal contusions are bruises or swelling in small, specific areas of the brain. This type of injury can be coup or contrecoup or both. Dr. Freeman, can you tell us about focal contusions?
Absolutely, Dr. Hemstad. Focal contusions can be caused by direct impact or rapid acceleration and deceleration. A coup injury occurs when the bruising is directly under the site of impact. A contrecoup injury happens when the side of the brain opposite the site of impact bruises. Contrecoup injuries are actually more common than coup injuries when the mechanism is direct impact.
When the mechanism is rapid or sudden acceleration and deceleration, a person is likely to have a coup-contrecoup injury. Rapid acceleration and deceleration means the brain inside the skull is being thrown back and forth. The result is bruising on both sides of the brain. Coup-contrecoup is also possible with direct impact injuries that create enough force to cause this violent back-and-forth motion of the brain inside the skull.