The consequences of mild traumatic brain injury are often anything but mild. Recent studies linking concussion to long-term neurologic deficits suggest that, for some individuals, the characteristic transient brain dysfunction and acute symptom resolution represent the beginning of potentially irreversible structural and functional brain alterations. “Traumatic brain injury occurs as a spectrum disorder. The term 'mild' describes only the initial insult relative to the degree of neurological severity. There may be no correlation with the degree of short- or long-term impairment or functional disability,” said Dr. Nathan Zasler of the University of Virginia, Charlottesville, and medical director of the Concussion...