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 regulate your sense of awareness and consciousness. It also acts as a filter that allows you to ignore unimportant information by focusing on details 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 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 brain cells that make up the RAS, which in turn triggers symptoms associated with concussion, such as:

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

Increased risk

The three main causes of 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 potential risks associated with concussion. But this is only if you (or your child) wear appropriate equipment, such as a helmet, and are 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 the sport should be made illegal.

Post-concussion syndrome (PCS) is the term used to describe a collection of symptoms that can last for several weeks or months after the concussion.

The exact cause of PCS is not known. One theory is that PCS is the result of a chemical imbalance in the brain triggered by the initial injury that caused the concussion. Another theory suggests that PCS may be caused by damage to nerve cells in the brain.

Symptoms of PCS

The symptoms of PCS fall into three main categories:

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

Physical symptoms of PCS include:

• headaches – often described as 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

Treating PCS

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

Antidepressants and talking treatments such as psychotherapy may help 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.

Due to the nature of concussion, most diagnoses are either made in the accident and emergency (A&E) department, 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 breathing is unaffected.

If you are conscious, you will be questioned 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 you have a serious neck or spinal injury until proved otherwise. Therefore it is recommended 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 paramedics arrive (dial 112 from elsewhere in Europe).

Further testing

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. 

However, if it is thought you may have damaged the bones in your neck an X-ray may be used to assess the damage quickly. CT scans are avoided on children under 10 where possible, but may be necessary in some cases (see below).

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.

Adults

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 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, such as loss of feeling in certain parts of the body, problems with balance and walking, and persistent changes in eyesight

A CT scan is 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 (for example, 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

Children

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 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).

Concussion is the sudden but short-lived loss of mental function that occurs after a blow or other injury to the head. Concussion is the most common but least serious type of brain injury.

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

When to seek medical help

Most people with mild concussion do not require any treatment as they normally get better by themselves. However, if there are signs of a more serious injury, they may need emergency treatment.

Phone 999 for an ambulance immediately if the person:

• remains unconscious after the initial injury
• is having a seizure or fit
• is bleeding from one or both ears
• is having difficulty staying awake, speaking, or understanding what people are saying

Read about the symptoms of concussion for more information on when to seek emergency medical care or visit an accident and emergency (A&E) department.

There are a number of things you can do at home to relieve concussion symptoms, these include:

• apply an ice pack to the injury to reduce swelling
• take paracetamol to control any pain
• avoid drinking alcohol or taking recreational drugs

Read more about how concussion is treated including information on self care tips and when you can return to playing sport.

Recovery

After experiencing concussion, a period of careful monitoring is needed. This can be for several days or weeks, depending on how serious the concussion was.

This is because the symptoms of concussion could also be symptoms of a more serious condition, such as:

• bleeding between the skull and the brain (subdural haematoma)
• bleeding on to the surface of the brain (subarachnoid haemorrhage)

Both of these conditions are medical emergencies. Go to your nearest accident and emergency (A&E) department as soon as possible if you or someone in your care shows any of the following signs:

• mental confusion
• drowsiness that goes on for longer than an hour
• difficulty speaking
• loss of balance
• persistent headache

Outlook

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 long-term problems or complications.

There is evidence that repeated episodes of concussion could cause long-term problems with mental abilities and trigger 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’.)

Post-concussion syndrome (PCS) is a poorly understood condition where symptoms of concussion can last for weeks or months afterwards.

Read more information about PCS as a complication of concussion.

Who’s at risk?

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.

Read more information about the causes of concussion and tips on preventing concussion.

There are a number of commonsense precautions you can take to reduce your risk of concussion.

These precautions include:

• always wear the recommended equipment when taking part in a contact sport such as rugby or boxing
• make sure any contact sport you or your child are taking part in is 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 you do not trip over anything
• use appropriate safety equipment if doing any kind of DIY
• use appropriate equipment to change a light bulb – such as a stepladder
• clean up spillages to prevent someone slipping over

For more information, go to the website for the Royal Society for the Prevention of Accidents.

Symptoms of concussion can be mild to severe and in some cases emergency treatment may be needed.

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 within a few hours.

Less common symptoms

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  
• 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 accident and emergency (A&E) department 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
• amnesia (memory loss), such as not being able to remember what happened before or after the injury
• 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

There are 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, such as warfarin, to prevent blood clots 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.

There are a number of self-care techniques you can use to relieve mild concussion symptoms. If more serious symptoms start to develop, seek immediate medical treatment.

Some self care techniques for mild symptoms of concussion 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. Do not use the non-steroidal anti-inflammatory drug (NSAID) type of painkillers, such as ibuprofen or aspirin, as these can sometimes cause bleeding at the site of the injury.
• 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 below 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 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 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 activity. 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 drills 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.