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Traumatic Brain Injury (TBI) - Definition, Epidemiology, Pathophysiology
Author: Segun T Dawodu, MD, JD, MBA, FAAPMR, FAANEM, CIME, DipMI(RCSed), Former Clinical Instructor, Mount Sinai Medical School; Current Director, Pain and Injuries Rehabilitation Services, PMRehab Pain and Sports Medicine Associates
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Updated: Mar 30, 2009

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Introduction

Definition

Traumatic brain injury (TBI) is a nondegenerative, noncongenital insult to the brain from an external mechanical force, possibly leading to permanent or temporary impairment ofcognitive, physical, and psychosocial functions, with an associated diminished or altered state of consciousness.

The definition of TBI has not been consistent and tends to vary according to specialties and circumstances. Often, the term brain injury is used synonymously with head injury, which may not be associated with neurologic deficits. The definition also has been problematic with variationsin inclusion criteria.

For excellent patient education resources, visit eMedicine's Back, Ribs, Neck, and Head Center. Also, see eMedicine's patient education article Concussion.

Epidemiology

Inconsistency in the definition and classification of traumatic brain injury (TBI), along with discrepancies in data collection, has made the epidemiology of TBI difficult to describe accurately.Problems with TBI data collection include the fact many patients with mild TBI may not present to the hospital, and the ones who do present may be discharged at the emergency department (ED) without adequate documentation. Severe TBI with associated death at the scene of the accident or during transport to a hospital also may not be accounted for completely in data collection for TBI epidemiologicstudies.

Differences in diagnostic tools and admission criteria also may affect the above-defined severity classifications. In the past, the use of roentgenograms to help diagnose skull fractures after head injury did not show much of any concurrent intracranial lesions. These lesions were difficult to diagnose until the advent of CT scanning, which is now the diagnostic imaging of choice inTBI cases.2,3

Other confounding variables in determining the epidemiology of TBI exist. The use of different definitions that may not clearly define the type of injury (see Synonyms, Key Words, and Related Terms) makes the epidemiology of TBI difficult to describe. Another variable is the difference in findings from diagnostic imaging at different time intervals (eg, when early epidural hematomais present, the CT scan may be normal, but if the scan is later repeated, it may show evidence of pathology).2,4

TBI accounts for approximately 40% of all deaths from acute injuries in the United States. Annually, 200,000 victims of TBI need hospitalization, and 1.74 million persons sustain mild TBI requiring an office visit or temporary disability for at least 1 day.

The financial cost isestimated at approximately $4 billion per year. This estimate includes the loss of potential income of the patient and of relatives (who may need to become caregivers), the cost of acute care, and other medical expenses, such as continuous ambulatory and rehabilitation care.

Mortality rate

Approximately 52,000 US deaths per year result from TBI. Local factors in the United States mayinfluence this mortality rate; it is lowest in the Midwest and Northeast and is highest in the South.

The mortality rate for deaths outside of the hospital is approximately 17 per 100,000 people; it is approximately 6 per 100,000 people for patients who are hospitalized.

The initial GCS score and, therefore, the severity of the TBI help to predict the likelihood of death from the injury. The...