The most common and least serious type of traumatic brain injury is called a concussion. The word comes from the Latin concutere, which means "to shake violently."
According to the CDC, between 2001 and 2009, an estimated 173,285 people under age 19 were treated in hospital emergency rooms for concussions related to sports and recreation activities. Other causes include car and bicycle accidents, work-related injuries, falls, and fighting.
As seen in countless Saturday morning cartoons, a concussion is most often caused by a sudden direct blow or bump to the head.
The brain is made of soft tissue. It's cushioned by spinal fluid and encased in the protective shell of the skull. When you sustain a concussion, the impact can jolt your brain. Sometimes, it literally causes it to move around in your head. Traumatic brain injuries can cause bruising, damage to the blood vessels, and injury to the nerves.