Concussion is also known as a mild traumatic brain injury (TBI).  This is caused by a bump or blow to the head.  Concussions can also occur from a fall or from trauma that causes the head and brain to move quickly back and forth.  Although concussions are usually not life-threatening, their effects can be serious.  Symptoms may include difficulty concentrating, memory problems, headaches, dizziness, blurry vision, and fatigue.