Traumatic Brain Injury

Traumatic brain injury (TBI) is damage to the brain caused by an external mechanical force, ranging from concussion to severe, life-threatening injury. It is a major cause of trauma death and long-term disability, and its management centres on grading severity, preventing secondary brain injury from hypoxia and hypotension, and monitoring neurological status over time.

Definition

Traumatic brain injury is an alteration in brain function, or other evidence of brain pathology, caused by an external mechanical force, with severity graded clinically — commonly using the Glasgow Coma Scale — from mild to severe.

Scope

This entry describes how TBI is classified by severity, the distinction between primary and secondary brain injury, the role of the Glasgow Coma Scale, and the principles of monitoring and preventing secondary insult. It is a reference and educational overview and does not provide individualised diagnostic thresholds, dosing, or treatment instructions.

Core questions

• How severe is the injury, and how is severity graded?
• What is primary injury versus secondary injury, and how is secondary injury prevented?
• How is neurological status and intracranial pressure monitored?
• What systemic factors (oxygenation, blood pressure) most influence outcome?

Key concepts

• Primary vs secondary brain injury
• Glasgow Coma Scale severity grading (mild, moderate, severe)
• Intracranial pressure and cerebral perfusion pressure
• Avoidance of hypoxia and hypotension
• Focal vs diffuse injury patterns
• Concussion and mild TBI
• Neurological monitoring and reassessment

Mechanisms

TBI involves a primary injury — the immediate mechanical disruption of brain tissue at the moment of impact — and a secondary injury that evolves over hours to days through processes such as ischaemia, oedema, raised intracranial pressure, and impaired cerebral perfusion. Much of TBI management aims to prevent or limit secondary injury, particularly by avoiding hypoxia and hypotension, which strongly worsen outcomes. The Glasgow Coma Scale provides a reproducible measure of consciousness used both to grade initial severity and to track change. In severe injury, monitoring of intracranial pressure and cerebral perfusion pressure guides care, as synthesised in the Brain Trauma Foundation guidelines, while the CRASH-3 trial examined antifibrinolytic therapy in acute TBI.

Clinical relevance

TBI is a leading contributor to trauma mortality and to lasting neurological disability, and emergency and critical-care nurses are central to serial neurological assessment, monitoring for deterioration, and supporting measures that protect the injured brain. This entry is educational; it describes how TBI is understood and monitored and is not a basis for individualised diagnosis or treatment.

Epidemiology

TBI affects many millions of people worldwide each year across all ages, with falls and road-traffic injury among the leading causes; it is a major global cause of injury death and of long-term disability, as detailed in the Lancet Neurology Commission on TBI.

History

The systematic clinical assessment of head injury was transformed by Teasdale and Jennett's introduction of the Glasgow Coma Scale in 1974, which gave a common, reproducible language for level of consciousness. Subsequent decades saw the development of intracranial-pressure monitoring and the Brain Trauma Foundation guidelines, and large-scale collaborative efforts such as the Lancet Neurology Commission framed TBI as a major global health problem.

Debates

What is the role of antifibrinolytic therapy in acute TBI?

The CRASH-3 trial examined whether tranexamic acid improves outcomes after traumatic brain injury, and the interpretation of its results across injury severities and timing remains an area of active discussion.

Key figures

• Graham Teasdale
• Bryan Jennett

Seminal works

• teasdale-jennett-1974
• carney-2017
• maas-2017

Frequently asked questions

What is the difference between primary and secondary brain injury?

Primary injury is the immediate mechanical damage at the moment of impact, while secondary injury develops afterward through processes such as swelling, raised pressure, and reduced blood flow; much of TBI care aims to limit secondary injury.

How is the severity of traumatic brain injury graded?

Severity is commonly graded clinically using the Glasgow Coma Scale, with categories typically described as mild, moderate, and severe based on the patient's level of consciousness.