A concussion occurs when the head sustains a hard blow and the impact jars or shakes the brain inside the skull, interrupting the brain's normal activities. Although there may be cuts or bruises on the head or face, there may be no other visible signs of a brain injury.

Symptoms of a concussion can include any of the following changes in the person's level of consciousness, such as:

• Loss of consciousness.
• Inability to remember what happened immediately before or after the injury (amnesia).
• Confusion.
• Asking the same question over and over.
• Dizziness, vertigo, light-headedness, or unsteadiness.
• Blurred or double vision.
• Ringing in the ears (tinnitus).
• Changes in personality.
• A decreased ability to talk or feed themself.
• Changes in how well a child is able to do physical activities, such as increased unsteadiness that makes it hard for the child to walk or stand.
• In a small child, increased fussiness or lack of energy.
• Ongoing headaches.

Symptoms of a concussion can be mild to severe, depending on the severity of the injury. If the injury is more serious, symptoms will usually develop within the first 24 hours. Symptoms may last for days, weeks, or even months following the injury.