MSD Manual

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Quick Facts



The Manual's Editorial Staff

Last full review/revision Oct 2019| Content last modified Oct 2019
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What is a concussion?

A concussion is an injury to your brain that temporarily affects your thinking and awareness.

The skull bone protects your brain. Fluid inside your skull also cushions your brain. However, if your head gets hit hard enough, your brain can move inside the skull and bump up against your skull. This may injure your brain and temporarily change the way your brain works.

  • You may be knocked out (unconscious), or you may just feel confused

  • Doctors will do a CT scan of your head to make sure your brain isn't bleeding or bruised

  • Once you get a concussion you can get future concussions more easily, especially if your brain hasn't healed

  • Repeated concussions may increase your chance of getting long-term brain damage and dementia

What causes a concussion?

Concussions are caused by something hitting your head very hard (head injury). This can happen when, for example, you:

  • Fall and hit your head

  • Are in a car or motorcycle crash

  • Get punched in the head or hit on your head with an object

Many sports have a risk of concussion (see Sports-Related Concussion).

What are the symptoms of a concussion?

If you have a concussion, you may:

  • Be unconscious for a while (usually for less than 15 minutes)

  • Feel dazed, confused, or light-headed

  • Answer questions slowly

  • Have a headache, double vision, or sensitivity to light

  • Be clumsy or have poor balance

  • Have trouble remembering what happened just before or after you got hurt

What is post-concussion syndrome?

Post-concussion syndrome is when you have symptoms after your concussion. You may have:

  • Headaches

  • Dizziness and light-headedness

  • Being tired, easily annoyed, or sensitive to light or noise

  • Trouble paying attention

  • Poor memory

  • Depression and anxiety

Usually these symptoms go away in a week or two. Less often, these symptoms last for months.

How can doctors tell if I have a concussion?

Your doctor can tell you've had a concussion based on the symptoms you had after having a head injury.

In order to tell whether you've had any brain injury, doctors will usually:

  • Do a CT scan of your head to make sure your brain isn't bleeding or bruised

You may not need a CT scan if your symptoms went away in a few minutes after your head injury.

How do doctors treat a concussion?

Your doctor will have you:

  • Rest

  • Take acetaminophen if you have a headache

Don’t play contact sports, which put you at higher risk of concussion, until your doctor says your head injury is completely healed and that you can return to play.

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