Some traumatic brain injuries can be seen on an MRI scan. Many, however, cannot. The structural MRI - Braindamage caused by the trauma is just too subtle. Of course, even subtle changes in brain structure can cause profound changes in brain functioning. Simply because  the brain injury cannot be seen on an MRI, it doesn’t mean that it

Doctors once believed that, whenever a blow to the head resulted in a brain injury, the victim would lose consciousness. Without a loss of consciousness, they would say, there could be no brain injury. That’s no longer the case. Now, medical professionals agree that a brain injury can result without the victim ever blacking out

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