What is a Traumatic Brain Injury?

Traumatic brain injury (TBI) occurs when a sudden trauma causes damage to or temporary disruption of the brain. TBI can result when the head suddenly and violently hits an object, when an object pierces the skull and enters brain tissue, or as a result of accelleration/ decellaration forces.  Symptoms of a TBI can be mild, moderate, or severe, depending on the presence or extent of the damage to the brain.  

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Mild TBI (concussion)

A concussion is a physiological disruption of brain function.  It results from a blow to the head or from acceleration/ deceleration forces. A cascade of neuron dysfunction is triggered that rapidly reverses itself, with return to normal metabolic function.   The terms “mild TBI” and “concussion” are used interchangeably in the research literature.

In 2004 The World Health Organization collaborative task force conducted a review of evidence based criteria, and published this consensus definition:

MTBI is an acute brain injury resulting from mechanical energy to the head from external physical forces. Operational criteria for clinical identification include:

(i)  1 or more of the following:

  1. confusion or disorientation,
  2. loss of consciousness for 30 minutes or less,
  3. post-traumatic amnesia for less than 24 hours, and/or other transient neurological abnormalities such as focal signs, seizure, and intracranial lesion not requiring surgery;

(ii)  Glasgow Coma Scale score of 13–15 after 30 minutes post-injury or later upon presentation for healthcare.

These manifestations of MTBI must not be due to drugs, alcohol, medications, caused by other injuries or treatment for other injuries (e.g. systemic injuries, facial injuries or intubation), caused by other problems (e.g. psychological trauma, language barrier or coexisting medical conditions) or caused by penetrating craniocerebral injury (p. 115).

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Moderate or Severe TBI

A person with a moderate or severe TBI may show these same symptoms, but may also have a headache that gets worse or does not go away, repeated vomiting or nausea, convulsions or seizures, an inability to awaken from sleep, dilation of one or both pupils of the eyes, slurred speech, weakness or numbness in the extremities, loss of coordination, and increased confusion, restlessness, or agitation

Types of Severe TBI

There are two types of severe TBI, each described below by associated causes:

Closed – an injury to the brain caused by movement of the brain within the skull. Causes may include falls, motor vehicle crash, or being struck by or with an object.

Penetrating – an injury to the brain caused by a foreign object entering the skull. Causes may include firearm injuries or being struck with a sharp object.

The Glasgow Coma Scale (GCS) is a clinical tool designed to assess coma and impaired consciousness. It is one of the most commonly used severity scoring systems.  

3 to 8 are classified with a severe TBI

9 to 12 are classified with a moderate TBI  

13 to 15 are classified with a mild TBI. 

Other classification systems include the Abbreviated Injury Scale (AIS), the Trauma Score, and the Abbreviated Trauma Score. 

Head Injury Help and Resources

Brain Injury Association: www.biausa.org