A concussion or traumatic brain injury (TBI) is a blow or a jolt to the head. The force of the blow makes the brain shake quickly back and forth. The injury may keep the brain from working normally. An injury to another part of the body that transmits force to the head can also cause a concussion. Symptoms of a concussion may last less than a day or may linger for months or longer.

Millions of mild traumatic brain injuries occur in the U.S. each year, but most don't require a visit to the hospital.

Many concussions that require emergency treatment are because of falls, motor vehicle accidents, assaults, and sports injuries. Children, young adults, active military personnel, and older adults are at especially high risk for concussions, and it may take them longer to recover after a concussion. People who have had concussions before are more likely to have them again.

Possible symptoms of a concussion include:

• Headache.
• Vomiting or nausea.
• Trouble thinking normally.
• Memory problems.
• Trouble walking.
• Dizziness.
• Vision problems.
• Severe tiredness (fatigue).
• Mood changes.
• Changes in sleep patterns.

These symptoms may occur right away or may worsen over minutes or hours after an injury. Symptoms may be stable or improve over time.

To diagnose a concussion, your doctor will likely ask you a variety of questions. Be sure to say if you lost consciousness and report any other symptoms. The doctor will also want to know how the injury occurred and where you hit your head.

You may also be asked questions to test your memory and asked to do certain tasks to show how well your brain is working. Your doctor may also ask your friends or family questions about your symptoms and the injury.

You may also need imaging tests of your brain, such as a CT (computerized tomography) scan or MRI (magnetic resonance imaging). Neuropsychological testing can detect problems with memory and other brain functions.

An important part of treatment for a concussion is getting plenty of rest, both sleep at night and naps or rest breaks during the day if needed. Your doctor will likely tell you to not do certain physical activities and sports while you recover. They may advise medicine to take if you have a headache. It's important to prevent more head trauma, especially as you recover.

If your symptoms don't go away in a few days or if they get worse, you should contact a doctor who specializes in concussions. You may need medicines, physical therapy, or other treatments for ongoing symptoms, such as headache, dizziness, or balance problems.

Here are some things you can do to help reduce your risk for a concussion or prevent it in your children:

• Wear a seat belt every time you're in a motor vehicle.
• Make sure your children use the correct safety seat, booster seat, or seat belt.
• Never drive under the influence of drugs or alcohol, or ride with a driver who is under the influence.
• Wear a helmet for activities such as riding a bike or motorcycle, playing contact sports, skiing, horseback riding, and snowboarding.
• Reduce your risk for falls by getting rid of clutter in your home, removing slippery area rugs, and installing grab bars in the bathroom if needed, especially for older adults.
• Never work on a ladder if you feel dizzy or lightheaded. Alcohol can make you dizzy. Some medicines also can make you dizzy or affect your balance.
• Have your vision checked at least once a year. Poor vision can increase your risk for falls and other types of accidents.

After a concussion, your doctor may decide to watch you in the emergency room, or overnight in the hospital. When you're released, the doctor may want someone to stay with you at home for a day or two to keep track of your condition. Follow your doctor's directions about not taking part in sports, physical education classes, and activities such as running and biking while you are recovering.

Limit activities that require you to concentrate a lot. This includes taking tests if you are in school or doing tasks at work that require intense focus. You may also need to take rest breaks during the day. As your symptoms go away, you may be able to go back to your normal activities. The time it takes to recover from a concussion can vary from weeks to months. In rare cases, symptoms can last for years.

Symptoms usually get better with time. If you have symptoms or problems that last more than 3 months, you may have a problem called post-concussion syndrome. You can discuss this with your doctor.

Call 911 or go to the emergency room if you or someone else loses consciousness after a blow to the head or if any of these occur:

• Headache that gets worse and doesn't go away
• Weakness, numbness, or decreased coordination
• Ongoing or worsening nausea or vomiting
• Slurred speech
• Confusion
• Drowsiness
• Convulsions or seizures

These could be signs of a serious condition that needs treatment right away.

• A blow or a jolt to the head can cause a concussion.
• Symptoms such as headache, nausea, vomiting, dizziness, or trouble thinking can happen right away. Or they may come on slowly over time.
• Call 911 or go to the emergency room if a person loses consciousness after a blow to the head.
• Getting plenty of rest is an important part of treating concussions.

Tips to help you get the most from a visit to your doctor:

• Know the reason for your visit and what you want to happen.
• Before your visit, write down questions you want answered.
• Bring someone with you to help you ask questions and remember what your doctor tells you.
• At the visit, write down the name of a new diagnosis and any new medicines, treatments, or tests. Also write down any new instructions your doctor gives you.
• Know why a new medicine or treatment is prescribed and how it will help you. Also know what the side effects are and when they should be reported.
• Ask if your condition can be treated in other ways.
• Know why a test or procedure is recommended and what the results could mean.
• Know what to expect if you do not take the medicine or have the test or procedure.
• If you have a follow-up appointment, write down the date, time, and purpose for that visit.
• Know how you can contact your doctor if you have questions, especially after office hours and on weekends and holidays.