Minor head injury and knocks to the head are common, particularly in children. Following the injury, if the person is conscious (awake), and there is no deep cut or severe head damage, it is unusual for there to be any damage to the brain.

However, sometimes a knock to the head can cause damage to the brain or to a blood vessel next to the brain. A damaged blood vessel may bleed into the brain, or more commonly, into the area between the brain and the skull (a 'subdural haemorrhage'). This is uncommon, but can be serious, as a build-up of clotting blood can cause pressure on the brain.

Symptoms of damage or bleeding may not develop for some hours, or even days, after a knock to the head. In rare cases, symptoms from a slow bleed can develop even weeks after a head injury.

This is why 'head injury instructions' are given to people who have had a head injury. These are symptoms to look out for following a knock to the head.

See a doctor quickly if any of the following symptoms occur after a head injury

- Drowsiness when you would normally be wide awake.
- Worsening headache - which does not go away with paracetamol.
- Confusion, strange behaviour, any problems understanding or speaking
- Continuous Vomiting.
- Loss of use of part of the body - for example, weakness in an arm or leg.
- Dizziness, loss of balance or walking strangely..
- Fitting (convulsions) or collapse followed by feeling strange afterwards..
- Any visual problems, such as blurring of vision or double vision.
- Blood or clear fluid leaking from the nose or ear.
- Unusual breathing patterns.

A note about drowsiness

After a knock to the head, children will often cry, be distressed and then settle down. It is then quite common for them to want to sleep for a short while. This is normal. However, it will appear to be a normal 'peaceful' sleep, and they wake up fully after a nap.

Some parents are afraid to let their children go to sleep if the accident happens just before bedtime. Do let them. Drowsiness means they cannot be roused. If you have a concern, wake the child up after an hour or so. They may be grumpy about being woken up, but that is reassuring. You can then let him or her go back off to sleep again. When asleep, check to see that he or she appears to be breathing normally and is sleeping in a normal position.

A note about headache

It is normal after a knock to the head to have a mild headache. Sometimes there is also tenderness over bruising or mild swelling of the scalp. Some paracetamol or ibuprofen will help. It is a headache that becomes worse and worse which is of more concern.

Some other symptoms that may occur

Some people develop some mild symptoms after a head injury that are not serious and usually go away within two weeks. These can include a mild headache, feeling a bit sick (without vomiting), being irritable and grumpy, tiredness, poor appetite and some difficulty concentrating. These may develop just as a reaction to a knock on the head and not due to bleeding or serious injury. However, if you have any doubt about a symptom following a head injury then it is best to get it checked out by a doctor as soon as possible. Also, see a doctor if you feel that you have not completely recovered after two weeks.