What is a brain injury?

A brain injury is defined as an alteration in brain function caused by an external force such as a blow, collision or jolt. This alteration in brain function may be temporary, long lasting or permanent; as such, concussion is a type of brain injury, including mild forms of concussion with short term effects.

A head injury is defined as damage caused to the skull, scalp, or any part of the protective layer around the brain. When a head injury occurs, there may be an impact upon the cells and nerves within the brain, causing a brain injury.

Anyone who has a head injury should be assessed for a potential brain injury, but one does not always follow the other. A person can suffer severe cuts to their head, for example, without incurring damage to the brain and equally, damage to the brain can occur without any visible external harm to the head.

Types of brain injuries

Any brain injury that occurs after birth, that is not the result of a congenital condition, is called an Acquired Brain Injury (ABI). An ABI may be the result of an internal process, such as a stroke, or caused by an external force, such as a blow to the head during sport or an accident. An external force brain injury is called a Traumatic Brain Injury (TBI). At Coulthursts, we are wholly focused on support for people with TBIs and it is this form of brain injury which will be considered in more detail here.

The assessment of traumatic brain injuries (TBIs)

The way traumatic brain injuries are assessed at present is based on two measures: duration of loss of consciousness and post traumatic amnesia (PTA). An injured person with PTA will be conscious, but may be talking or behaving in a strange, uncharacteristic way. There is likely to be short term memory loss and difficulties processing what has happened to them and where they are. They may recognise family and friends. A person may have PTA without having had any loss of consciousness.

This framework is commonly used for classifying the severity of brain injuries:

  • Very severe brain injury: loss of consciousness for 48 hours or more
  • Severe brain injury: loss of consciousness for 6 to 48 hours, post-traumatic amnesia for 24 hours to 7 days
  • Moderate brain injury: loss of consciousness for 15 minutes to 6 hours, post-traumatic amnesia for one to 24 hours
  • Minor brain injury: loss of consciousness for less than 15 minutes (or no loss of consciousness at all) and post-traumatic amnesia for less than one hour

Is this an accurate way of predicting outcomes?

This framework for classifying brain injuries is shaped by the principles of triage in accident and emergency hospital departments. It helps clinicians to decide who should have immediate access to CT and MRI scans, who should stay in hospital for monitoring and care (severe and moderate) and who can be sent home with advice (mild).

The main shortcoming of this system is for the large category of people assessed as having a minor traumatic brain injury (mTBI). Approximately 90 per cent of people with a brain injury are classified as mild. These patients may not be offered a brain scan, or if they are, the scan may not identify any damage. They may be told they have concussion, sent home and told they will recover over time.

However, a significant proportion of patients do not make a full recovery and experience long term difficulties. A recent study found 53 per cent of patients classified as having mild traumatic brain injuries still reported functional deficits a year after their original injury occurred (Nelson et al, 2019). Functional deficits included difficulties completing tasks, concentrating and social functioning.


Nelson LD, Temkin NR, Dikmen S, et al. Recovery After Mild Traumatic Brain Injury in Patients Presenting to US Level I Trauma Centers: A Transforming Research and Clinical Knowledge in Traumatic Brain Injury (TRACK-TBI) Study. JAMA Neurol. 2019;76(9):1049–1059. doi:10.1001/jamaneurol.2019.1313

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Learn More

Brain Injuries

A brain injury is defined as an alteration in brain function caused by an external force such as a blow, collision or jolt.


Concussion may be caused by a direct blow or jolt. For example, a collision during sport or a road traffic accident.

Head Injuries

A head injury is any sort of injury to your brain, skull, or scalp. It can range in severity from a bump or bruise to a major skull fracture requiring surgery.

Post-concussion syndrome

Post-concussion syndrome is an umbrella term for a cluster of difficulties that are present three months or more after an injury.

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    We are happy to provide further guidance on our services and information about concussion, head and brain injuries and do so without charge.

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