A traumatic brain injury (TBI) is any sudden injury to your brain. It happens when a bump, blow, jolt, or other injury damages the brain. It can occur from a strong or violent strike to your head. It also can occur when an object, like a bullet or piece of skull, pierces your brain tissue. TBIs can be mild, moderate, or severe, depending on how much damage there is. Concussions are a mild form of TBI. They cause temporary symptoms that usually go away a few days or weeks after the injury. The most severe TBIs can cause permanent brain damage, coma, or death. Some symptoms of a traumatic brain injury happen immediately after the traumatic event. Others may not appear for several days or weeks. For a mild injury, it’s normal to feel dizzy, nauseated, or have a headache. Other mild symptoms include: Ringing in your ears, Neck pain, Blurry vision, Confusion, Slow reflexes, Brief loss of consciousness