Causes of concussion

Causes of concussion

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:

Increased risk

The three main causes of concussion are:

  • being involved in a road accident
  • an 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 any 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 of 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.

Diagnosing concussion

Diagnosing concussion

Because of the nature of concussion, most diagnoses are either made at an 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 perform 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, as a precaution it is assumed that you have a serious neck or spinal injury until proved otherwise. You should therefore not be 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.

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.

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 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 vomited 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 are 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


A CT scan may be 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 signs and symptoms that suggest the base of the skull is fractured, such as "panda eyes"
  • have memory loss
  • have a large bruise or wound to the face or head

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).

Treating concussion

Treating concussion

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 a cold compress to the injury to reduce swelling - a bag of frozen vegetables wrapped in a towel could be used, but never place ice directly on the skin as it's too cold; apply the compress every two to four hours and leave it in place for 20 to 30 minutes
  • take paracetamol to control pain - do not use non-steroidal anti-inflammatory drug (NSAID) painkillers such as ibuprofen or aspirin as these can sometimes cause bleeding at the site of the injury
  • get plenty of rest and avoid stressful situations where possible
  • 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 for at least three weeks without seeing your GP first - this includes sports such as football and rugby
  • make sure you have someone to stay with you for the first 48 hours after the injury - this is in case you experience more serious follow-up symptoms

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. This means it's 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 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 from 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 2013 conference of experts in sports medicine recommended these steps:

  1. complete rest until symptoms have passed for at least 24 hours
  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

If you are symptom-free, you should be able to return to play within a week. If you experience a return of symptoms, rest for 24 hours, drop down to a previous step, and then attempt to move up again.

Complications of concussion

Complications of concussion

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 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 can 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
  • feeling sick (nausea)
  • sensitivity to bright lights
  • sensitivity to loud noises
  • ringing in the ears - the medical term for this is tinnitus
  • double or blurred vision
  • fatigue
  • lost, changed or reduced sense of smell and taste

Psychological symptoms of PCS can include:

  • depression
  • anxiety 
  • irritability
  • lack of energy and interest in the world around you
  • having problems sleeping
  • changes in appetite
  • 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
  • difficulty remembering things or learning new information
  • difficulties with reasoning (working out problems)

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 caused by PCS.

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 1 in 10 people will still have symptoms after a year.