A concussion happens when your brain comes into contact with the inside of your skull. This can happen in a car crash or other traumatic event. The concussion can lead to the following symptoms immediately after the incident: headache, loss of consciousness, nausea, vomiting, ringing in the ears, blurred vision, slurred or unclear speech, drowsiness, dizziness, confusion, foggy mental state, and an inability to remember what just happened.