An impact on one side of the head can cause the pudding-like substance of the brain to hit the inside of the skull and then bounce back and hit the inside of the skull on the opposite side of the head.  When the brain suffers two injuries from one impact, it is called a “coup contrecoup,” or “coup contra coup” injury. Sometimes, the secondary (contrecoup) injury is more damaging than the primary (coup) injury. To complicate things, internal bleeding and swelling from the primary injury can mask the brain damage caused by the secondary injury.  One of my clients went weeks before sophisticated imaging of his brain and neuroevaluations showed that his cognitive problems were almost all due to a “contrecoup injury,” rather than the more obvious “coup” injury.