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.

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 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

Children

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).