A concussion is a temporary disruption of brain function caused by a sudden force transmitted to the head. We worry about concussions for a few reasons. The first is the rare chance that another blow to the head, even a mild one, while the brain is still vulnerable from the first injury could lead to severe brain swelling. Secondly, there is concern that multiple concussions could eventually add up to permanent problems with thinking and memory. Finally, even if they are short-lived, concussion symptoms can interfere with learning and social interaction during a crucial period of development in a young person’s life.