Mild traumatic brain injury is a category of bran injury that includes concussion, with concussion being at the mildest end of that spectrum. So sports concussion, for example, would be a subset of mild traumatic brain injury, all of the patients in this study received a CT scan to evaluate for brain bleeding or skull fracture and may have had a neurological deficit when they came to the emergency room. While that type of injury can be classified as' mild,' it's a lot more severe than a sport-related concussion typically would be.