Coup Contrecoup Injury - Mechanisms

Mechanisms

Coup injury may be caused when, during an impact, the skull is temporarily bent inward and impacts the brain. When the skull bends inward, it may set the brain into motion, causing it to collide with the opposite side of the skull; this will result in a contrecoup injury. The injuries can also be caused solely by acceleration or deceleration, in the absence of an impact. In injuries associated with acceleration or deceleration but with no impact, the brain is thought to bounce off the inside of the skull and hit the opposite side, potentially resulting in both coup and contrecoup injuries. In addition to the skull, the brain may also impact the tentorium, causing a coup injury. Contrecoup injury may be produced by tensile forces.

Cerebrospinal fluid (CSF) is also implicated in the mechanism of coup and contrecoup injuries. One explanation for the contrecoup phenomenon is that CSF, which is denser than the brain, rushes to the area of impact during the injury, forcing the brain back into the other side of the skull. If this is the case, the contrecoup impact happens first.