How severe is the brain injury?

After a traumatic brain injury, whether or not the person was actually unconscious, a state occurs where the person seems to be aware of things around them but is confused and disorientated. They are not able to remember everyday things or conversations, and often do or say bizarre things. This is called Post-Traumatic Amnesia (PTA), and is a stage through which the person will pass.

The length of PTA and/or loss of consciousness are important as they give an indication of the severity of the injury.

The term 'Coma' is often used to describe longer periods of unconsciousness.

The table below gives a rough guide to how these measures affect the severity of the injury, although it is worth noting that everyone is different and categorising injuries in this way doesn't always give an accurate measure of the long-term effects.

  Loss of consciousness Post traumatic amnesia
Mild brain injury < 15 mins < 1 hour
Moderate brain injury 15 mins - 6 hours 1 hour - 24 hours
Severe brain injury 6 hours - 48 hours 24 hours - 7 days
Very severe brain injury > 48 hours > 7 days

Our factsheets Post traumatic amnesia and Coma and reduced awareness states describe these in more detail. Download them now from the 'Related resources' section.

Mild brain injury and concussion

Concussion - also known as mild brain injury or mild head injury - is commonly caused by falls, road crashes, assaults and sports accidents. It is estimated that over a million people each year attend accident and emergency departments in the UK after a head injury, with the majority of these injuries being classed as minor.

The effects of concussion can leave people with symptoms including dizziness, nausea, confusion or an inability to process or retain information, sensitivity to light, and vision distortion.

Visit our Mild head injury and concussion page to find out more.

Moderate brain injury

A moderate brain injury is defined as loss of consciousness for between 15 minutes and 6 hours, or a period of post-traumatic amnesia of up to 24 hours. The patient can be kept in hospital overnight for observation, and then discharged if there are no further obvious medical injuries. Patients with moderate head injury are likely to suffer from a number of residual symptoms.

The most commonly reported symptoms include tiredness, headaches and dizziness (physical effects) difficulties with thinking, attention, memory planning, organising, concentration and word-finding problems (cognitive effects) and irritability (a behavioural problem).

These symptoms are accompanied by understandable worry and anxiety. This can be particularly pronounced if the patient has not been warned that these problems are likely to arise. If the patient expects to be perfectly well within a few days and symptoms are still prominent after a few weeks, they may worry or feel guilty. This has the effect of creating a vicious circle leading to more symptoms and so on.

A large proportion of people find that when they return to work they have difficulties and feel that they are not functioning at their highest level. For the majority of people these residual symptoms gradually improve, although this can sometimes take 6 to 9 months.

Severe brain injury

Severe brain injury is usually defined as being a condition where the patient has been in an unconscious state for 6 hours or more, or a post-traumatic amnesia of 24 hours or more. These patients are likely to be hospitalised and receive rehabilitation once the acute phase has passed. Depending on the length of time in coma, these patients tend to have more serious physical deficits.

A further category of very severe injury is defined by a period of unconsciousness of 48 hours or more, or a period of PTA of 7 days or more. The longer the length of coma and PTA, the poorer will be the outcome. However, there are exceptions to this rule and, just as there is a small group of people who have a mild head injury who make a poor recovery, so there is a small group of individuals who have a severe or very severe injury who do exceptionally well.