A concussion is a traumatic brain injury that alters the way your brain functions. Effects are usually temporary but can include headaches and problems with concentration, memory, balance and coordination.

Although concussions usually are caused by a blow to the head, they can also occur when the head and upper body are violently shaken. These injuries can cause a loss of consciousness, but most concussions do not. Because of this, some people have concussions and don't realize it.

Concussions are common, particularly if you play a contact sport, such as football. But every concussion injures your brain to some extent. This injury needs time and rest to heal properly. Most concussive traumatic brain injuries are mild, and people usually recover fully.

The signs and symptoms of a concussion can be subtle and may not be immediately apparent. Symptoms can last for days, weeks or even longer.

Common symptoms after a concussive traumatic brain injury are headache, loss of memory (amnesia) and confusion. The amnesia, which may or may not follow a loss of consciousness, usually involves the loss of memory of the event that caused the concussion.

Signs and symptoms of a concussion may include:

• Headache or a feeling of pressure in the head
• Temporary loss of consciousness
• Confusion or feeling as if in a fog
• Amnesia surrounding the traumatic event
• Dizziness or "seeing stars"
• Ringing in the ears
• Nausea
• Vomiting
• Slurred speech
• Delayed response to questions
• Appearing dazed
• Fatigue

Some symptoms of concussions may be immediate or delayed in onset by hours or days after injury, such as:

• Concentration and memory complaints
• Irritability and other personality changes
• Sensitivity to light and noise
• Sleep disturbances
• Psychological adjustment problems and depression
• Disorders of taste and smell

Symptoms in children

Head trauma is very common in young children. But concussions can be difficult to recognize in infants and toddlers because they may not be able to describe how they feel. Nonverbal clues of a concussion may include:

• Appearing dazed
• Listlessness and tiring easily
• Irritability and crankiness
• Loss of balance and unsteady walking
• Crying excessively
• Change in eating or sleeping patterns
• Lack of interest in favorite toys

When to see a doctor

See a doctor within 1 to 2 days if:

• You or your child experiences a head injury, even if emergency care isn't required

The American Academy of Pediatrics recommends that you call your child's doctor for advice if your child receives anything more than a light bump on the head.

If your child doesn't have signs of a serious head injury, and if your child remains alert, moves normally and responds to you, the injury is probably mild and usually doesn't need further testing. In this case, if your child wants to nap, it's OK to let him or her sleep. If worrisome signs develop later, seek emergency care.

Seek emergency care for an adult or child who experiences a head injury and symptoms such as:

• Repeated vomiting
• A loss of consciousness lasting longer than 30 seconds
• A headache that gets worse over time
• Changes in his or her behavior, such as irritability
• Changes in physical coordination, such as stumbling or clumsiness
• Confusion or disorientation, such as difficulty recognizing people or places
• Slurred speech or other changes in speech

Other symptoms include:

• Seizures
• Vision or eye disturbances, such as pupils that are bigger than normal (dilated pupils) or pupils of unequal sizes
• Lasting or recurrent dizziness
• Obvious difficulty with mental function or physical coordination
• Symptoms that worsen over time
• Large head bumps or bruises on areas other than the forehead in children, especially in infants under 12 months of age

Athletes

No one should return to play or vigorous activity while signs or symptoms of a concussion are present.

Experts recommend that an athlete with a suspected concussion not return to play until he or she has been medically evaluated by a health care professional trained in evaluating and managing concussions. Children and adolescents should be evaluated by a health care professional trained in evaluating and managing pediatric concussions.

Experts also recommend that adult, child and adolescent athletes with a concussion not return to play on the same day as the injury.

Your brain has the consistency of gelatin. It's cushioned from everyday jolts and bumps by cerebrospinal fluid inside your skull. A violent blow to your head and neck or upper body can cause your brain to slide back and forth forcefully against the inner walls of your skull.

Sudden acceleration or deceleration of the head, resulting from certain events such as a car crash or being violently shaken, also can cause brain injury.

These injuries affect brain function, usually for a brief period, resulting in signs and symptoms of concussion.

A brain injury of this sort may lead to bleeding in or around your brain, causing symptoms such as prolonged drowsiness and confusion that may develop right away or later.

Such bleeding in your brain can be fatal. That's why anyone who experiences a brain injury needs monitoring in the hours afterward and emergency care if symptoms worsen.

Factors that may increase your risk of a concussion include:

• Participating in a high-risk sport, such as football, hockey, soccer, rugby, boxing or other contact sport; the risk is further increased if there's a lack of proper safety equipment and supervision
• Being involved in a motor vehicle collision
• Being involved in a pedestrian or bicycle accident
• Being a soldier involved in combat
• Being a victim of physical abuse
• Falling, especially in young children and older adults
• Having had a previous concussion

Potential complications of concussion include:

• Epilepsy. People who have had a concussion double their risk of developing epilepsy within the first five years after the injury.
• Cumulative effects of multiple brain injuries. Evidence exists indicating that people who have had multiple concussive brain injuries over the course of their lives may acquire lasting, and even progressive, impairment that limits their ability to function.
• Post-concussion syndrome. Some people begin having post-concussion symptoms — such as headaches, dizziness and thinking difficulties — a few days after a concussion. Symptoms may continue for weeks to a few months after a concussion.
• Post-traumatic headaches. Some people experience headaches within a week to a few months after a brain injury.
• Post-traumatic vertigo. Some people experience a sense of spinning or dizziness for days, week or months after a brain injury.

• Second impact syndrome. Experiencing a second concussion before signs and symptoms of a first concussion have resolved may result in rapid and usually fatal brain swelling.

  After a concussion, the levels of brain chemicals are altered. It usually takes about a week for these levels to stabilize again. However, recovery time is variable, and it's important for athletes never to return to sports while they're still experiencing signs and symptoms of concussion.

It's important for anyone who has a head injury to be evaluated by a doctor, even if emergency care isn't required.

If your child has received a head injury that concerns you, call your child's doctor immediately. Depending on the signs and symptoms, your doctor may recommend seeking immediate medical care.

Here's some information to help you get ready for and make the most of your medical appointment.

What you can do

• Be aware of any pre-appointment restrictions or instructions. The most important thing for you to do while waiting for your appointment is to rest your brain physically and mentally. Avoid sports or vigorous physical activities and minimize difficult, stressful or prolonged mental tasks.

  At the time you make the appointment, ask what steps you or your child should take to encourage recovery or prevent re-injury. Experts recommend that athletes not return to play until they have been medically evaluated.

• List any symptoms you or your child have been experiencing and the length of time you or your child have been experiencing them.
• Write down key medical information, including other medical problems for which you or your child are being treated and any history of previous head injuries. Also write down the names of any medications, vitamins, supplements or other natural remedies you or your child are taking.
• Take a family member or friend along. Sometimes it can be difficult to soak up all the information provided to you during an appointment. Someone who accompanies you may remember something that you missed or forgot.
• Write down questions to ask your doctor.

For a concussion, some basic questions to ask your doctor include:

• Is it a concussion?
• What kinds of tests are needed?
• What treatment approach do you recommend?
• How soon will symptoms begin to improve?
• What is the risk of future concussions?
• What is the risk of long-term complications?
• When will it be safe to return to competitive sports?
• When will it be safe to resume vigorous exercise?
• Is it safe to return to school or work?
• Is it safe to drive a car or operate power equipment?
• I have other medical problems. How can they be managed together?
• Should a specialist be consulted? What will that cost, and will my insurance cover seeing a specialist? You may need to call your insurance provider for some of these answers.
• Are there any brochures or other printed material that I can take home with me? What websites do you recommend?

In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask questions during your appointment.

What to expect from your doctor

Being ready to answer your doctor's questions may reserve time to go over any points you want to talk about in-depth.

You or your child should be prepared to answer the following questions about the injury and related signs and symptoms:

• Do you play contact sports?
• How did you get this injury?
• What symptoms did you experience immediately after the injury?
• Do you remember what happened right before and after the injury?
• Did you lose consciousness after the injury?
• Did you have seizures?
• Have you experienced nausea or vomiting since the injury?
• Have you had a headache? How soon after the injury did it start?
• Have you noticed any difficulty with physical coordination since the injury?
• Have you had any problems with memory or concentration since the injury?
• Have you noticed any sensitivity or problems with your vision and hearing?
• Have you had any mood changes, including irritability, anxiety or depression?
• Have you felt lethargic or easily fatigued since the injury?
• Are you having trouble sleeping or waking from sleep?
• Have you noticed changes in your sense of smell or taste?
• Do you have any dizziness or vertigo?
• What other signs or symptoms are you concerned about?
• Have you had any previous head injuries?

What you can do in the meantime

Rest as much as possible before your appointment. This includes avoiding sports or other physical activities that increase your heart rate, such as prolonged walking, or require vigorous muscle contractions, such as weightlifting.

Also, minimize activities that increase your symptoms, such as those that require a significant amount of focused attention. Examples include working on the computer, schoolwork, watching TV, texting or playing video games.

If you have a headache, acetaminophen (Tylenol, others) may ease the pain. Avoid taking other pain relievers such as aspirin or ibuprofen (Advil, Motrin IB, others) if you suspect you've had a concussion. It's possible that these may increase the risk of bleeding.

A blow to your head, neck or upper body can cause a concussion, which may include symptoms such as a headache, dizziness, nausea or loss of consciousness. If you suspect you or your child has had a concussion, contact your doctor.

Your doctor will evaluate your signs and symptoms, review your medical history, and conduct a neurological examination. Signs and symptoms of a concussion may not appear until hours or days after the injury.

Tests your doctor may perform or recommend include:

Neurological examination

After your doctor asks detailed questions about your injury, he or she may perform a neurological examination. This evaluation includes checking your:

• Vision
• Hearing
• Strength and sensation
• Balance
• Coordination
• Reflexes

Cognitive testing

Your doctor may conduct several tests to evaluate your thinking (cognitive) skills during a neurological examination. Testing may evaluate several factors, including your:

• Memory
• Concentration
• Ability to recall information

Imaging tests

Brain imaging may be recommended for some people with symptoms such as severe headaches, seizures, repeated vomiting or symptoms that are becoming worse. Brain imaging may determine whether the injury is severe and has caused bleeding or swelling in your skull.

A cranial computerized tomography (CT) scan is the standard test to assess the brain right after injury. A CT scan uses a series of X-rays to obtain cross-sectional images of your skull and brain.

Magnetic resonance imaging may be used to view bleeding in your brain or to diagnose complications that may occur after a concussion.

An MRI uses powerful magnets and radio waves to produce detailed images of your brain. 

Observation

You may need to be hospitalized overnight for observation after a concussion.

If your doctor agrees that you may be observed at home, someone should stay with you and check on you for at least 24 hours to ensure your symptoms aren't worsening. Your caregiver may need to awaken you regularly to make sure you can awaken normally.

Rest is the most appropriate way to allow your brain to recover from a concussion. Your doctor will recommend that you physically and mentally rest to recover from a concussion.

This means avoiding general physical exertion, including sports or any vigorous activities, until you have no symptoms.

This rest also includes limiting activities that require thinking and mental concentration, such as playing video games, watching TV, schoolwork, reading, texting or using a computer.

Your doctor may recommend that you have shortened school day or workdays, take breaks during the day, or have reduced school workloads or work assignments as you recover from a concussion.

As your symptoms improve, you may gradually add more activities that involve thinking, such as doing more schoolwork or work assignments, or increasing your time spent at school or work.

For headaches, try taking a pain reliever such as acetaminophen (Tylenol, others). Avoid other pain relievers such as ibuprofen (Advil, Motrin IB, others) and aspirin, as there's a possibility these medications may increase the risk of bleeding.

If you or your child sustained a concussion while playing competitive sports, ask your doctor or your child's doctor when it is safe to return to play. Resuming sports too soon increases the risk of a second concussion and of lasting, potentially fatal brain injury.

Evidence is emerging that some people who have had multiple concussions over the course of their lives are at greater risk of developing lasting, and even progressive, impairment that limits their ability to function.

No one should return to play or vigorous activity while signs or symptoms of a concussion are present.

Experts recommend that adults, children and adolescents not return to play on the same day as the injury.

Some tips that may help you to prevent or minimize your risk of head injury include:

• Wearing protective gear during sports and other recreational activities. Always use the appropriate protective gear for any sport you or your child undertakes. Make sure the equipment fits properly, is well-maintained and worn correctly. Follow the rules of the game and practice good sportsmanship.

  When bicycling, motorcycling, snowboarding or engaging in any recreational activity that may result in head injury, wear protective headgear.

• Buckling your seat belt. Wearing a seat belt may prevent serious injury, including an injury to your head, during a traffic accident.
• Making your home safe. Keep your home well-lit and your floors free of anything that might cause you to trip and fall. Falls around the home are a leading cause of head injury.
• Protecting your children. To help lessen the risk of head injuries to your children, block off stairways and install window guards.
• Exercising regularly. If you're older, exercise regularly to strengthen your leg muscles and improve your balance.
• Educating others about concussions. Educating coaches, athletes, parents and others about the features of a concussion, how to evaluate a concussion, and how to determine when it's appropriate to return to play or school can help spread awareness and knowledge about concussions. Coaches and parents can also help encourage good sportsmanship.