Coup contrecoup injuries commonly happen as a result of direct impacts. They occur when an external force or object hits the head and rocks the brain violently back and forth inside the skull. The brain is primarily impacted at the location of the force and is pushed to the opposite side of the head where it strikes the skull, causing two separate injuries.
‘Coup’ essentially means the injury caused by the initial impact and ‘contrecoup’ means the injury on the opposite side of the brain. ‘Coup contrecoup’ injuries have two separate and opposite injury sites that resulted from the same impact.
Imagining your brain as a bouncy ball inside a jar helps to visualize how this works. When you shake the jar, the ball bounces side to side. You stop shaking the jar and the ball still bounces less an less until it eventually stops.
The same thing happens to your brain inside the skull in a coup contrecoup injury. The first impact forces your brain to bounce against the opposite side of the jar, your skull, which forces it in the opposite direction again. The brain moves back and forth until it eventually stops rocking
This movement causes tearing in different parts of the brain, some of which may never heal. When tissue and nerves tear, important connections are broken. The brain has to create new pathways to send information or it will be permanently impaired.