Severe head injuries can cause serious complications, mainly because the brain can be damaged, sometimes permanently.
A particularly severe head injury can be fatal. A person with this type of injury will be closely monitored in hospital so any complications that arise can be dealt with promptly and effectively.
If your skull is fractured during a head injury, you may have a greater risk of developing an infection.
Skull fractures can occasionally tear the membrane (the thin layer of cells) that surrounds the brain.
If this happens, bacteria can enter the wound and cause an infection.
It's important that any external wounds on your head are kept clean so they don't become infected.
You may also be prescribed antibiotics.
Some people may experience long-term symptoms after sustaining concussion from a head injury. This could be post-concussion syndrome.
The symptoms and effects of post-concussion syndrome can include:
These symptoms usually clear up in around 3 months, but you may need to be referred for further assessment by your GP.
You may be seen by a neurologist, who specialises in problems of the nervous system (brain, spinal cord and nerves), or a psychiatrist (mental health specialist).
Find out more about post-concussion syndrome
Some people who sustain a severe head injury enter a state of impaired consciousness, such as a coma, vegetative state or minimally conscious state.
These disorders of consciousness affect wakefulness (the ability to open your eyes and have basic reflexes) and awareness (more complex thoughts and actions, such as following instructions, remembering and communicating).
These states sometimes only last a few weeks, after which time a person may wake up or progress into a different state of impaired consciousness.
But they can last years and some people will never regain consciousness.
Find out more about treating disorders of consciousness
A severe head injury can damage the brain in several ways.
For example, brain damage can occur as a result of increased pressure on the brain caused by a blood clot between the skull and the surface of the brain (subdural haematoma) or bleeding in and around the brain (subarachnoid haemorrhage).
There's also an increased risk of epilepsy.
A person who develops epilepsy after a head injury may need medication for a period of time or for life.
Brain injuries can also lead to a number of other problems, which can be temporary or permanent.
The effect of a brain injury will depend on:
The different effects of a brain injury are described below.
Physical effects of a brain injury can include difficulty moving or keeping your balance and loss of co-ordination.
You may also experience headaches or increased tiredness.
Some head injuries can damage the pituitary gland, a small gland that sits at the base of the brain and regulates the thyroid.
If the pituitary gland is damaged, it may lead to reduced hormone production and problems such as an underactive thyroid (hypothyroidism).
You may lose your sense of taste and smell.
You may also notice blind spots in your vision, or you may not be able to control your body temperature as well as before so you feel too hot or too cold.
After a head injury, you may find it difficult to think, process information and solve problems.
You may also experience memory problems, particularly with your short-term memory, and have difficulty with speech and communication skills.
After a severe head injury, you may experience changes to your feelings and behaviour. For example, you may be angrier or more easily irritated than before.
You may be less sensitive to other people's feelings, or lose your inhibitions and behave in a way that other people consider inappropriate.
You may also laugh or cry more than you did before the injury.
Some people go on to develop a mental health condition after a severe head injury, such as:
Contact your GP for advice if you think you have one or more of the above conditions.
As every brain injury is different, it's a good idea to seek further information about the possible effects and rehabilitation techniques.
A number of charities and organisations may be able to help, including: