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.