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Page last reviewed: 13/07/2011

Concussion is the sudden but short-lived loss of mental function that occurs after a blow or other injury to the head. The medical term for concussion is minor traumatic brain injury. Symptoms of concussion include:

  • brief loss of consciousness
  • memory loss
  • disturbances in vision, such as "seeing stars"
  • confusion

How common is concussion?

Concussion is the most common but least serious type of brain injury. It is estimated that one in every 2,000 people will experience an episode of concussion requiring hospital treatment each year.

However, the actual figure could be much higher, as many people do not seek treatment for concussion. Researchers from the World Health Organization estimated that the true number of people affected by concussion each year could be as high as one in 165.

At-risk groups

Most cases of concussion occur in children and teenagers aged five to 14, with the two most common causes being sporting and cycling accidents.

Falls and motor vehicle accidents are a more common cause of concussion in older adults.

People who regularly play competitive team sports such as football and rugby have a higher risk of concussion.


Most people with concussion do not require any treatment as they normally get better by themselves.

However, they will require a period of careful monitoring, ranging from several days to several weeks, depending on the severity of the concussion.

This is because what are assumed to be the symptoms of concussion could in fact be the symptoms of a more serious condition, such as bleeding that develops between the skull and the brain (subdural or extradural haematoma) or onto the surface of the brain (subarachnoid haemorrhage), both of which are medical emergencies.


The outlook for most cases of concussion is very good. While the medical term "minor traumatic brain injury" can sound serious, the actual extent of damage to the brain is usually minimal and does not usually cause any long-term problems or complications.

There is evidence that repeated episodes of concussion could cause long-term problems with mental abilities and trigger the onset of dementia. This type of dementia is known as chronic traumatic encephalopathy (CTE).

However, this seems to only be a significant risk for professional athletes who experience repeated episodes of severe concussion, such as boxers (CTE is sometime nicknamed "boxer's brain".)

Page last reviewed: 13/07/2011

The most common symptoms of concussion are:

  • headache
  • dizziness
  • nausea
  • loss of balance
  • confusion, such as being unaware of your surroundings
  • feeling stunned or dazed
  • disturbances with vision, such as double vision or seeing "stars" or flashing lights
  • difficulties with memory (see below)

Difficulties with memory can take one of two forms, or possibly both forms:

  • retrograde amnesia - where you are unable to remember events that occurred before the concussion happened. This usually only affects the minutes immediately leading up to the concussion.
  • anterograde amnesia - where you are unable to remember any new information or events after the concussion happened.

Both retrograde and anterograde amnesia usually improve over the space of a few hours.

Less common signs and symptoms of concussion include:

  • loss of consciousness
  • vomiting
  • slurred speech
  • "glassy eyes" and a vacant stare
  • changes in behaviour, such as feeling unusually irritable
  • inappropriate emotional responses, such as suddenly bursting into laughter or tears 

When to seek emergency medical treatment

The following signs and symptoms suggest it is likely that the head injury has caused serious damage and you should phone 999 for an ambulance immediately:

  • remaining unconscious after the initial injury
  • difficulty staying awake or still being sleepy several hours after the injury
  • having a seizure or fit
  • difficulty speaking, such as slurred speech
  • prolonged vision problems, such as double vision
  • difficulty understanding what people say
  • reading or writing problems
  • balance problems or difficulty walking
  • loss of power in part of the body, such as weakness in an arm or leg
  • "pins and needles" in the hands or feet
  • amnesia (memory loss), such as not being able to remember what happened before or after the injury
  • clear fluid leaking from the nose or ears (this could be cerebrospinal fluid, which normally surrounds the brain)
  • a black eye, with no other damage around the eye
  • bleeding from one or both ears
  • sudden deafness in one or both ears

When to seek medical advice

As a precaution it is recommended that you visit your nearest emergency department (A&E) if you or someone in your care has a head injury resulting in concussion and then develops any of the following signs and symptoms:

  • loss of consciousness from which the person then recovers
  • loss of memory of events that happened before or after the injury (or both)
  • persistent headaches since the injury
  • persistent vomiting since the injury
  • changes in behaviour, such as irritability, being easily distracted or having no interest in the outside world - this is a particularly common sign in children under the age of five
  • confusion
  • drowsiness that goes on for longer than an hour when you would normally be awake
  • problems understanding or speaking
  • loss of balance or problems walking
  • weakness in any limb
  • clear fluid or blood coming out of the ear or nose
  • sudden deafness in one or both ears

There are also a number of factors that make you more vulnerable to the effects of a head injury:

  • being aged 65 or older
  • having a previous history of having brain surgery
  • having a condition that makes you bleed more easily, such as haemophilia, or having a condition that makes your blood more prone to clotting, such as thrombophilia
  • taking anticoagulant medication to prevent blood clots, such as warfarin or low-dose aspirin

It is also recommended that anyone who is drunk or high on recreational drugs is taken to A&E if they have a head injury resulting in concussion. It is often easy for others around them to miss signs and symptoms of a more severe injury.

Page last reviewed: 13/07/2011

Concussion occurs when a blow or impact to the head causes a sudden disruption to part of the brain known as the reticular activating system (RAS).

The RAS is located in the middle of your brain and helps to regulate your sense of awareness and consciousness. It also acts as a type of filter that allows you to ignore unimportant information by only focusing on the details that you need.

For example, your RAS helps you to:

  • fall asleep and wake up as required
  • suddenly hear when your flight is being called in a noisy airport
  • notice news items that interest you when you are quickly scanning a newspaper or news website

During a head injury that is severe enough to cause concussion, your brain is moved out of its normal position for a short time. This rotation disrupts the electrical activities of the brain cells that make up the RAS, which in turn triggers the symptoms associated with concussion, such as:

  • loss of memory
  • a brief period of unconsciousness
  • mental confusion

Risk factors

The three main risk factors for concussion are:

  • being involved in a road accident
  • accidental trip or fall
  • taking part in sporting or other recreational activities

Activities known to have a higher-than-average risk of concussion include:

  • rugby
  • football
  • cycling
  • boxing
  • martial arts, such as karate or judo

Most doctors would argue that the physical benefits of regularly taking part in these sports outweigh the potential risks associated with concussion. But this is only if you (or your child) wear the appropriate equipment, such as a helmet, and you are being supervised by a suitably trained referee, umpire or trainer with experience in diagnosing and treating concussion.

The exception to this is boxing, as most doctors, especially those who treat head injuries, have stated that the risks of serious brain injury associated with boxing are unacceptably high and that the sport should be made illegal.

Page last reviewed: 13/07/2011

Due to the nature of concussion, most diagnoses are either made in the Emergency Department (ED), by a paramedic at the scene of an accident or by a trained official at a sporting event.

The person making the diagnosis will make a careful physical examination to check if there are any noticeable signs and symptoms of a more serious brain injury, such as bleeding from the ears, while making sure that your breathing is unaffected.

If you are conscious, you will be asked some questions so your state of mind (particularly your memory) can be assessed.

Possible questions include:

  • Where are we?
  • What were you doing before the concussion?
  • Can you repeat the months of the year in reverse order?

You may be asked to try what is known as the "finger-nose-finger" test. The person running the test will hold one of their fingers in front of you. You are asked to touch their finger and then touch the tip of your nose as quickly as possible.

This test is a good way of assessing what effect the concussion has had on your balance and co-ordination.

If you are unconscious, then as a precaution it is recommended to assume that you have a serious neck or spinal injury until proved otherwise. Therefore it is recommended that you are not moved until a specialist brace can be fitted around your neck and spine to protect it.

Similarly, if you see a person who is unconscious, make no attempt to move them unless they are in immediate physical danger. Instead, dial 999 for an ambulance and wait with them until the paramedics arrive (dial 112 from elsewhere in Europe).

CT scan

In some circumstances, further testing may be recommended if there are any signs or symptoms that suggest a more serious injury to your brain.
The most widely used test for suspected brain injury is a computerised tomography (CT) scan. 

A CT scan takes a series of X-rays of the inside of your skull and puts them together using a computer. The image that is created forms a cross-section of the inside of your skull and brain.


A CT scan is usually recommended in adults who:

  • have persistent problems in speaking, carrying out instructions or opening their eyes
  • have signs and symptoms that suggest that the base of the skull is fractured, such as clear fluid running from the nose or ears or very dark blotches above and below the eyes ("panda eyes")
  • have a seizure or fit after the injury
  • have been sick more than once since the injury
  • are unable to remember events more than 30 minutes before the injury
  • have any signs of neurological problems (problems affecting the brain and nervous system), such as loss of feeling in certain parts of the body, problems with balance and walking, and persistent changes in eyesight

A CT scan may also recommended for adults who have experienced some loss of consciousness or memory since the injury and who:

  • are aged 65 or over
  • have a problem that makes them prone to uncontrollable bleeding, such as a blood clotting disorder such as haemophilia or taking the anticoagulant medication warfarin
  • were injured in a particularly serious accident, such as a road accident or falling from a height of more than one metre (1.1 yards)


A CT scan is usually recommended in children who:

  • lost consciousness for more than five minutes
  • are unable to remember what happened before or after the injury and this has lasted more than five minutes
  • are unusually drowsy
  • have been sick three times or more since the injury
  • had a seizure or fit after the injury
  • have persistent problems speaking, carrying out instructions or opening their eyes
  • have any sign that the skull may be pushing against their brain, such as an unusual swelling in their head
  • have signs and symptoms that suggest that the base of the skull is fractured, such as "panda eyes"
  • have any signs of a neurological problem (problems affecting the brain and nervous system)
  • were injured in a high-speed road accident as a pedestrian, cyclist or passenger
  • fell from a height of more than three metres
  • were injured by an object travelling at high speed, such as a cricket ball

A CT scan is also usually recommended for babies less than a year old who have a bruise, swelling or cut on the head bigger than 5cm (2 inches).

Page last reviewed: 13/07/2011

There are a number of self-care techniques you can use to relieve concussion symptoms, which are outlined below.

  • Apply ice to the head injury to help reduce swelling. Do not apply ice directly to your scalp as this could damage the skin. Instead, wrap the ice in a washcloth or towel. Alternatively, a bag of frozen vegetables such as peas could be used. Apply the ice every two to four hours and leave in place for 20-30 minutes.
  • Take paracetamol to control pain. Other painkillers can be prescribed but it is probably best to be seen by a doctor if the headache is not controlled by paracetamol.
  • Take plenty of rest and, where possible, avoid stressful situations.
  • Avoid drinking any alcohol or taking recreational drugs.
  • Only return to work, college or school when you feel you have completely recovered.
  • Only drive a car or ride a bike when you feel you have completely recovered.
  • Do not play any contact sports such as football or rugby for at least three weeks without talking to your GP (see box, left, for more information on returning to sport).
  • Make sure you have someone to stay with you for the first 48 hours after the injury, in case you experience more serious follow-up symptoms (see below).

When to seek follow-up advice

Sometimes the symptoms of a more serious brain injury do not occur for several hours or possibly days after the initial injury has taken place.

So, it is important that you remain alert for signs and symptoms that could suggest a more serious injury has occurred.

If you or someone in your care has any of the signs or symptoms listed below, go to your nearest accident and emergency (A&E) department as soon as possible:

  • unconsciousness or lack of consciousness, such as problems keeping your eyes open
  • mental confusion such as forgetting who or where you are
  • any drowsiness that goes on for longer than one hour when you would normally be wide awake
  • any problems understanding or speaking
  • any loss of balance or problems walking
  • any weakness in one or both arms or legs
  • any problems with eyesight
  • a very painful headache that will not go away
  • any vomiting
  • any fits or seizures
  • clear fluid coming out of the ear or nose
  • bleeding from one or both ears
  • sudden deafness in one or both ears

Returning to sports

Despite being one of the most common sport-related injuries, there is no internationally agreed consensus on the advice about when it is safe to return to playing a contact sport, such as rugby, after a concussion.

Most national sporting federations and organisations recommend a "step-wise" approach where you wait until you are free of symptoms and then resume a low level of physical activities. If the symptoms do not return, you can step up to a more intense level of activity.

If symptoms are still under control, continue to step up through the levels, eventually returning to playing the sport.

A 2008 conference of experts in sports medicine recommended these steps:

  1. Complete rest until symptoms have passed.
  2. Light aerobic exercise such as walking and cycling.
  3. Sport-specific exercises such as running drill for football or rugby (but no activity that involves impact to the head).
  4. Non-contact training such as passing drills for football.
  5. Full training including physical contact such as tackling.
  6. Return to play.

    Each step should take 24 hours, so if you are symptom-free you should be able to return to play within a week.

    If you do experience a return of symptoms, rest for 24 hours, drop down to a previous step, and then attempt to move up again.

Page last reviewed: 13/07/2011

Post-concussion syndrome

Post-concussion syndrome (PCS) is a poorly understood complication of concussion. In cases of PCS, the symptoms of concussion can last for several weeks or months.

The symptoms of PCS fall into three main categories:

  • physical
  • psychological
  • cognitive (affecting a person's thinking ability)

Physical symptoms of PCS include:

  • headaches - many people describe them as being similar to migraines, in that they cause a throbbing pain on one side or the front of the head
  • dizziness
  • sensitivity to bright lights
  • sensitivity to loud noises
  • ringing in the ears - the medical term for this is tinnitus
  • blurred vision
  • fatigue
  • lost or changed sense of smell and taste

Psychological symptoms of PCS include:

  • depression
  • anxiety
  • irritability
  • lack of energy and interest in the world around you
  • sudden and inappropriate outbursts of emotion, such as having fits of laughter or crying for no apparent reason

Cognitive symptoms of PCS include:

  • decreased concentration
  • forgetfulness
  • difficulties with learning new information
  • difficulties with reasoning

There are two main theories regarding the cause of PCS.

The first theory argues that PCS is the result of a chemical imbalance in the brain that was triggered by the initial injury that caused the concussion.

The second theory suggests that PCS may in fact be an emotional and psychological response to the initial injury; possibly a milder form of post-traumatic stress disorder (PTSD). PTSD is when a person develops a range of both physical and psychological symptoms after a traumatic event such as a serious car accident.

Experts cannot agree how many people with concussion will go on to develop this complication. Estimates have ranged widely from 30% to up to 90%.

The issue is further confused because research has found that rates of reported cases of PCS are much lower in countries where there is little to no possibility of obtaining financial compensation after an accident. This could suggest that at least a minority of cases of PCS are faked for financial gain.

However, it should not be assumed that all cases of PCS are faked, as many cases have been confirmed with testing.

There is no specific treatment for the symptoms of PCS, though many of the medications used to treat migraines have also proved effective in treating the headaches.

Antidepressants have helped control the psychological symptoms such as depression and anxiety.

Most cases of PCS will resolve within three to six months and only one in 10 people will still have symptoms after a year.

Page last reviewed: 13/07/2011

There are a number of basic common-sense precautions you can take to reduce your risk of concussion, such as:

  • Always wear the recommended equipment when taking part in a contact sport like rugby or boxing.
  • Make sure that any contact sport you or your child is taking part in is being supervised by a properly qualified and trained person.
  • Always wear a seatbelt when driving in a car.
  • Wear a motorcycle helmet - this is a legal requirement if you are riding a motorcycle in this country.
  • Wear a cycle helmet. This is not a legal requirement, but cycle helmets have been recommended by several leading organisations, such as the Royal Society for the Prevention of Accidents.

It is also easy to underestimate how many cases of concussion occur due to a fall or slip at home or in the garden, especially in older people. Following some or all of the suggestions below will help to keep your home and garden as safe as possible:

  • Keep stairways clear so that you do not trip over anything.
  • Use appropriate safety equipment if you are doing any kind of DIY.
  • Do not stand on an unstable chair to change a light bulb; use a stepladder.
  • Clean up any spillages to prevent someone slipping over.

Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.

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