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

Concussions are usually caused by a blow to the head. Violently shaking of the head and upper body also can cause concussions.

Some concussions cause you to lose consciousness, but most do not.

Falls are the most common cause of concussion. Concussions are also common if you play a contact sport, such as football or soccer. Most people usually recover fully after a concussion.

The signs and symptoms of a concussion can be subtle and may not show up immediately. 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 usually involves forgetting the event that caused the concussion.

Physical signs and symptoms of a concussion may include:

• Headache
• Ringing in the ears
• Nausea
• Vomiting
• Fatigue or drowsiness
• Blurry vision

Other signs and symptoms of a concussion include:

• Confusion or feeling as if in a fog
• Amnesia surrounding the traumatic event
• Dizziness or "seeing stars"

A witness may observe these signs and symptoms in the concussed person:

• Temporary loss of consciousness (though this doesn't always occur)
• Slurred speech
• Delayed response to questions
• Dazed appearance
• Forgetfulness, such as repeatedly asking the same question

You may have some symptoms of concussions immediately, and some can occur for days after the 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 can't describe how they feel. Concussion clues may include:

• Dazed appearance
• Listlessness and tiring easily
• Irritability and crankiness
• Loss of balance and unsteady walking
• Excessive crying
• Change in eating or sleeping patterns
• Lack of interest in favorite toys
• Vomiting
• Seizures

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

If your child doesn't have signs of a serious head injury, 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 signs and symptoms such as:

• Repeated vomiting or nausea
• A loss of consciousness lasting longer than 30 seconds
• A headache that gets worse over time
• Fluid or blood draining from the nose or ears
• Vision or eye disturbances, such as pupils that are bigger than normal (dilated pupils) or pupils of unequal sizes
• Ringing in the ears that doesn't go away
• Weakness in the arms or legs
• Appearing very pale for longer than an hour
• Changes in behavior
• Confusion or disorientation, such as difficulty recognizing people or places
• Slurred speech or other changes in speech
• Obvious difficulty with mental function or physical coordination
• Changes in physical coordination, such as stumbling or clumsiness
• Seizures or convulsions
• Lasting or recurrent dizziness
• 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

Never 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 activities that are associated with a higher risk of another concussion while still showing concussion symptoms.

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 concussions 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, caused by 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.

This type of brain injury may lead to bleeding in or around your brain, causing symptoms such as prolonged drowsiness and confusion. These symptoms may develop immediately 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.

Activities and factors that may increase your risk of a concussion include:

• Falling, especially in young children and older adults
• Participating in a high-risk sport, such as football, hockey, soccer, rugby, boxing or other contact sport
• Participating in high-risk sports without 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
• Having had a previous concussion

Potential complications of concussion include:

• Post-traumatic headaches. Some people experience concussion-related headaches up to seven days after a brain injury.
• Post-traumatic vertigo. Some people experience a sense of spinning or dizziness for days, weeks or months after a brain injury.
• Post-concussion syndrome. A small proportion of people (15% to 20%) may have symptoms including headaches, dizziness and thinking difficulties that persist beyond three weeks. If these symptoms persist beyond three months, this becomes characterized as post-concussion syndrome.
• Cumulative effects of multiple brain injuries. Active research is currently underway to study the effects of repeated head injuries that don't cause symptoms (subconcussive injury). At this time, there's no conclusive evidence indicating that repeated brain injuries contribute to cumulative effects.

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

  It's important for athletes never to return to sports while they're still experiencing signs and symptoms of concussion.

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. Make sure the equipment fits properly, is well maintained and is 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 head injury, 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. Exercise regularly to strengthen your leg muscles and improve your balance.
• Educating others about concussions. Educating coaches, athletes, parents and others about concussions can help spread awareness. Coaches and parents can also help encourage good sportsmanship.

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 a neurological examination, cognitive testing and imaging tests.

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 signs and 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 the skull.

A cranial computerized tomography (CT) scan is the standard test in adults 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.

For children with suspected concussion, CT scans are only used if there are specific criteria met, such as the type of injury or signs of a skull fracture. This is to avoid radiation exposure in young children.

Magnetic resonance imaging (MRI) may be used to identify changes 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 that your symptoms aren't worsening.

Your caregiver may need to awaken you regularly to make sure you can awaken normally.

There are steps you can take to help your brain heal and speed recovery.

Physical and mental rest

In the first few days after a concussion, relative rest is the most appropriate way to allow your brain to recover. Your doctor will recommend that you physically and mentally rest to recover from a concussion.

Relative rest, which includes limiting activities that require thinking and mental concentration, is recommended for the first two days after a concussion. However, complete rest, such as lying in a dark room and avoiding all stimuli, does not help recovery and is not recommended. In the first 48 hours, you should overall limit activities that require high mental concentration — such as playing video games, watching TV, doing schoolwork, reading, texting or using a computer — if these activities cause your symptoms to worsen.

You also should avoid physical activities that increase any of your symptoms, such as general physical exertion, sports or any vigorous movements, until these activities no longer provoke your symptoms.

After a period of relative rest, it's recommended that you gradually increase daily activities such as screen time if you can tolerate them without triggering symptoms. You can start both physical and mental activities at levels that do not cause a major worsening of symptoms. Light exercise and physical activity as tolerated starting a few days after injury have been shown to speed recovery; however, you should avoid any activities that have a high risk of exposure to another head impact until you are fully recovered.

Your doctor may recommend that you have shortened school days or workdays, take breaks during the day, or have modified or reduced school workloads or work assignments as you recover from a concussion. Your doctor may recommend different therapies as well, such as rehabilitation for vision, rehabilitation for balance problems, or cognitive rehabilitation for problems with thinking and memory.

Returning to routine activity

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.

Your doctor will tell you when it's safe for you to resume light physical activity. Usually after the first few days after injury, you're allowed to do light physical activity — such as riding a stationary bike or light jogging — before your symptoms are completely gone, so long as it doesn't significantly worsen symptoms.

Eventually, once all signs and symptoms of concussion have resolved, you and your doctor can discuss the steps you'll need to take to safely play sports again. Resuming sports too soon increases the risk of another brain injury.

Pain relief

Headaches may occur in the days or weeks after a concussion. To manage pain, ask your doctor if it's safe to take a pain reliever such as acetaminophen (Tylenol, others). Avoid other pain relievers such as ibuprofen (Advil, Motrin IB, others) and aspirin, as these medications may increase the risk of bleeding.

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 avoid activities that cause or worsen your symptoms. 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 has been experiencing and how long they've been occurring.
• List key medical information, including other medical problems for which you or your child is 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 is taking.
• Take a family member or friend along. Sometimes it can be difficult to remember all the information provided to you during an appointment. Someone who comes with you may recall something that you missed or forgot.
• Write down questions to ask your doctor.

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

• Do I have 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 that come up 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

The most important thing to do before your appointment is to avoid activities that significantly increase your symptoms and those that have an increased risk of another head impact. This includes avoiding sports or other physical activities that increase your heart rate, such as running, or require vigorous muscle contractions, such as weightlifting.

Gradually resume your normal daily activities, including screen time, as you're able to tolerate them without significantly worsening symptoms.

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. These may increase the risk of bleeding.