A coup-contrecoup brain injury occurs when the brain sustains damage at two opposite locations within the skull. The 'coup' injury happens at the point of impact, where external force directly strikes the head. The 'contrecoup' injury occurs on the opposite side of the brain, where the brain tissue rebounds and collides with the interior skull surface. This dual-impact mechanism distinguishes coup-contrecoup injuries from other types of traumatic brain injuries.
The biomechanics of coup-contrecoup injuries involve rapid acceleration and deceleration forces that cause the brain to move within the cerebrospinal fluid. When a sudden impact occurs, the brain's momentum carries it forward against the skull at the impact site (coup). The brain then bounces back and strikes the opposite side of the skull (contrecoup), creating a second injury site. Both locations can experience bruising (contusions), bleeding, tissue tearing, and cellular damage.
Medical imaging such as CT scans and MRIs typically reveal injury patterns on opposite sides of the brain in coup-contrecoup cases. These injuries can affect different brain regions with distinct functions, leading to a complex array of symptoms and deficits. The severity can range from mild concussions to severe traumatic brain injuries requiring intensive medical intervention and long-term rehabilitation.