A concussion is a minor traumatic brain injury that may occur when the head hits an object, or a moving object strikes the head.

It can affect how the brain works for a while. A concussion can lead to a bad headache, changes in alertness, or loss of consciousness.

A concussion can result from a fall, sports activities, or car accidents. A big movement of the brain (called jarring) in any direction can cause a person to lose alertness (become unconscious). How long the person stays unconscious may be a sign of the severity of the concussion.

Concussions do not always result in loss of consciousness. Most people who have a concussion never pass out. But they may describe seeing all white, black, or stars. A person can also have a concussion and not realize it.

Watch this video about: Concussion

Symptoms of a concussion range from mild to severe. They can include:

• Acting confused, feeling spacey, or not thinking straight
• Being drowsy, hard to wake up, or similar changes
• Headache
• Loss of consciousness
• Memory loss (amnesia) of events before the injury or right after
• Nausea and vomiting
• Seeing flashing lights
• Feeling like you have "lost time"

The following are emergency symptoms of a concussion. Seek medical care right away if there are:

• Changes in alertness and consciousness
• Confusion that does not go away
• Convulsions (seizures)
• Muscle weakness on one or both sides
• Persistent confusion
• Pupils of the eyes that are not equal in size
• Remaining unconsciousness (coma)
• Repeated vomiting
• Unequal pupils
• Unusual eye movements
• Walking or balance problems
• Unconsciousness (coma) that continues

Head injuries that cause a concussion often occur with injury to the neck and spine. Take special care when moving people who have had a head injury.

While recovering from a concussion, the person may:

• Be withdrawn, easily upset, or confused
• Have a hard time with tasks that require remembering or concentrating
• Have mild headaches
• Be less tolerant of noise
• Be very tired

The doctor will perform a physical exam. The person's nervous system will be checked. There may be changes in the person's pupil size, thinking ability, coordination, and reflexes.

Tests that may be ordered include:

• EEG (brain wave test) may be needed if seizures continue
• Head CT scan
• MRI of the brain

A more serious head injury that involves bleeding or brain damage must be treated in a hospital.

For a mild head injury no treatment may be needed. But be aware that the symptoms of a head injury can show up later.

• Friends or family may need to keep an eye on adults for symptoms after they are released from the emergency room or doctor’s office.
• Parents or caregivers of children need to keep an eye on a child for symptoms after a head injury.
• Both adults and children must follow the health care provider’s instructions about when the person can return to sports.

After even a mild concussion:

• Do not do activities that can cause further head injury.
• Avoid tasks that require concentration or complicated thinking. These include reading, homework, and preparing reports.
• Avoid bright lights and loud sounds. These can overstimulate the brain.

Recovering from a concussion takes time.

• It may take days, weeks, or even months.
• The person have trouble concentrating and may be unable to remember things. The person may be irritable, have headaches, dizziness, blurry vision, and nausea that comes and goes.
• Adults should get help from family or friends before making important decisions. This is because reasoning and thinking processes may be impaired.

In a small group of patients, symptoms of the concussion do not go away. The risk of long-term changes in the brain is high if the person has more than one brain injury

Seizures may occur after more severe head injuries.

Call the health care provider if a head injury causes changes in alertness or produces any other worrisome symptoms.

If symptoms do not go away or are not improving after 2 or 3 weeks, talk to the doctor.

Call the doctor right away if the following symptoms occur:

• Changes in behavior or unusual behavior
• Changes in speech (slurred, difficult to understand, does not make sense)
• Confusion
• Difficulty waking up or becoming more sleepy
• Double vision or blurred vision
• Fever
• Fluid or blood leaking from the nose or ears
• Headache that is getting worse, lasts a long time, or does not get better with over-the-counter pain relievers
• Problems walking or talking
• Seizures (jerking of the arms or legs without control)
• Vomiting more than three times

Not all head injuries can be prevented.  But the following simple steps can help keep you and your child safe:

• Always use safety equipment during activities that could cause a head injury. These include seat belts, bicycle or motorcycle helmets, and hard hats.
• Learn and follow bicycle safety recommendations.
• Do not drink and drive. Do not allow yourself to be driven by someone who you know or suspect has been drinking alcohol or is otherwise impaired.

Biros MH, Heegard WG. Head injury. In: Marx JA, Hockberger RS, Walls RM, et al., eds. Rosen's Emergency Medicine: Concepts and Clinical Practice. 7th ed. Philadelphia, PA: Elsevier Mosby; 2009:chap 38.

Hunt T, Asplund C. Concussion assessment and management. Clin Sports Med. 2009;5-17.

Landry GL. Head and neck injuries. In: Kliegman RM, Stanton BF, St. Geme JW III, et al., eds. Nelson Textbook of Pediatrics.19th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 680.