You have been diagnosed with a concussion. This is a type of brain injury caused by a sudden impact to your head. It can also be caused by sudden movement of your brain inside your head, such as from forceful shaking. Some concussions are mild. But even mild concussions are serious and must be managed with care and appropriate medical follow-up. Most people recover completely from mild concussions. But recovery may take days, weeks, or months. For some, symptoms may last even longer. Early care and monitoring are important to prevent long-term complications.