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INTRODUCTION

The purpose of this chapter is to review current epidemiology of traumatic brain injury (TBI) and classify the different types of TBI according to underlying pathology. For the purpose of this review, TBI is defined as “a traumatically induced structural injury and/or physiological disruption of brain function as a result of an external force.” Examples of such injuries include head strike by an object, rapid acceleration/deceleration-related injuries with damage to brain tissue, and penetration by a foreign body which induces brain injury. TBI is characterized by new onset or worsening of at least one of the following clinical signs or symptoms immediately following the event:

  • Any period of loss or a decreased level of consciousness (LOC)

  • Any loss of memory for events immediately before or after the injury (i.e., post-traumatic amnesia)

  • Any alteration in mental state at the time of injury (i.e., confusion, disorientation, slowed thinking)

  • Neurologic deficits (i.e., weakness, loss of balance, change in vision, praxis, sensory loss, aphasia) that may or may not be transient

The ever-growing body of epidemiological studies contributes to our current understanding of TBI. Worldwide, the incidence of TBI is 235 to 556 per 100,000 people. Data released in 2015 by the Centers for Disease Control and Prevention (CDC) and the National Center for Injury Prevention and Control (NCIPC)1 reported that approximately 1.7 million traumatic brain injuries annually. Eighty percent of these cases were reported from emergency department (ED) visits and 16.3% (275,000) from hospitalization. Three percent (52,000) resulted in death. In the United States, TBI comprises 30.5% of all injury-related deaths. According to the same CDC/NCIPC report, the total combined rates of TBI-related ED visits, hospitalizations, and deaths have increased from 521.0/100,000 in 2001 to 823.7/100,000 in 2010. This is largely due to the proportionate rise of ED visits in comparison to hospitalizations and deaths. It has been proposed that a greater awareness of TBI is what caused an increase in ED visits. In terms of prevalence, approximately 5.3 million individuals are living with TBI and its sequelae currently in the United States.

There are several striking gender differences among those with TBI. Rates are higher for males than for females, at a ratio of 2.5:1, and mortality rates in males are three to four times greater.

Regarding age, the populations most likely to sustain a TBI include 0 to 4 years, 15 to 19 years, and 65 years and older. The highest rates of death occur in those aged 65 and older. The age group with the highest rate of TBI-related ED visits is 0 to 14 years, and the age group with the highest rate of TBI-related hospitalizations occurs in patients greater than 65 years.

Causes of TBI have been found to vary with the different age groups. The National Hospital Ambulatory Medical Care Survey on Emergency Department Visits (2006–2010) characterizes the primary injury mechanism underlying TBI-related deaths by age. ...

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