Traumatic Brain Injury

Traumatic brain injury (TBI) is an alteration in brain function, or other evidence of brain pathology, caused by an external mechanical force. It ranges from mild concussion to severe injury with coma, and its neurosurgical management centres on grading severity, identifying surgical mass lesions on imaging, and preventing the secondary injury that determines much of the eventual outcome.

Definition

Traumatic brain injury is brain dysfunction or structural injury caused by an external mechanical force, conventionally graded by depth and duration of impaired consciousness (commonly via the Glasgow Coma Scale) into mild, moderate, and severe categories.

Scope

This entry covers TBI as a neurosurgical and critical-care entity: severity classification using the Glasgow Coma Scale, the pathophysiology of primary and secondary injury, the role of imaging in detecting surgical lesions, and the principal interventions studied in trials, including decompressive craniectomy. It is a reference overview and not a management protocol.

Core questions

• How is TBI severity defined and measured?
• What pathophysiological processes constitute secondary injury after the initial impact?
• Which imaging findings indicate a surgically treatable lesion?
• What does trial evidence show about decompressive craniectomy for raised intracranial pressure?

Key concepts

• Glasgow Coma Scale (mild, moderate, severe)
• Diffuse axonal injury
• Cerebral contusion
• Secondary injury cascade
• Raised intracranial pressure
• Decompressive craniectomy
• Cerebral perfusion pressure

Key theories

Primary versus secondary injury

The initial mechanical force produces primary injury (contusion, axonal shearing, vascular tear) that is largely fixed, while a subsequent cascade of hypoxia, hypotension, raised intracranial pressure, ischaemia, and inflammation produces secondary injury that is potentially modifiable and frames acute care.

Mechanisms

Mechanical loading produces focal lesions (contusions, lacerations) and diffuse axonal injury from rotational shearing. The injured brain then undergoes a secondary cascade: impaired autoregulation, excitotoxicity, oedema, and ischaemia, often compounded by systemic hypoxia or hypotension. Because the cranial compartment is fixed, swelling and haematoma raise intracranial pressure and threaten perfusion; decompressive craniectomy removes part of the skull to relieve this pressure, an intervention whose effect on survival and disability has been examined in randomised trials (Cooper et al., 2011; Hutchinson et al., 2016).

Clinical relevance

TBI is a major cause of death and acquired disability, and its severity grading and imaging triage shape how patients are routed through emergency and neurosurgical care. This entry explains the concepts and the evidence base so the literature can be read critically; it is descriptive and does not provide treatment instructions.

Epidemiology

Traumatic brain injury affects an estimated tens of millions of people annually and is characterised as a leading global contributor to injury-related death and disability, with falls and road traffic incidents as principal mechanisms and a rising share in older adults (Maas et al., 2017).

Evidence & guidelines

The Brain Trauma Foundation guidelines (Carney et al., 2016) summarise the evidence for managing severe TBI. Randomised trials of decompressive craniectomy, DECRA (Cooper et al., 2011) and RESCUEicp (Hutchinson et al., 2016), inform the debate over surgical decompression for refractory intracranial hypertension. These works are cited to map the evidence, not to direct care.

History

The 1974 Glasgow Coma Scale (Teasdale & Jennett) standardised the assessment of impaired consciousness and remains the basis for TBI severity grading. Subsequent decades brought CT-based triage, evidence-based severe-TBI guidelines, and randomised trials of decompressive surgery that refined and sometimes contested earlier surgical practice.

Debates

What is the role of decompressive craniectomy for refractory intracranial hypertension?

DECRA found that early bifrontal craniectomy for diffuse injury lowered intracranial pressure but was associated with worse functional outcomes, whereas RESCUEicp found that last-tier craniectomy reduced mortality at the cost of more survivors with severe disability; the balance of benefit and harm remains contested.

Key figures

• Graham Teasdale
• Bryan Jennett
• Andrew Maas
• Peter Hutchinson
• D. James Cooper

Seminal works

• teasdale-jennett-1974
• carney-2016
• hutchinson-2016
• cooper-2011

Frequently asked questions

How is the severity of a traumatic brain injury classified?

Severity is most commonly graded with the Glasgow Coma Scale into mild, moderate, and severe categories, based on eye, verbal, and motor responses; imaging and the duration of impaired consciousness add further detail.

Does removing part of the skull (decompressive craniectomy) improve outcomes after severe TBI?

Trials give a mixed picture: it reliably lowers intracranial pressure and can reduce mortality, but some survivors are left with severe disability, so its benefit depends on the clinical situation and remains debated.