Definition of traumatic brain injury

The Centers for Disease Control and Prevention (CDC) defines a traumatic brain injury (TBI) as an “injury to the head from blunt or penetrating trauma or from acceleration–deceleration forces resulting in one or more of the following: period of decreased or loss of consciousness, any amnesia before or after the injury, objective neurological deficits, any altered consciousness (i.e. confusion, disorientation, slowed thinking).” Forces from explosive blasts, particularly among US service members, can also cause TBI.

Traumatic brain injury classification

TBIs occur across a spectrum of severity and are classified based on specific factors ( Table 6.1 ), with the majority of TBIs (75%–90%) categorized as being mild TBI. The majority of patients who sustain a mild TBI experience symptom resolution with no lasting clinical sequelae. However, approximately 10% of these patients experience persistent symptoms. ^,

Statistics on TBI are limited and likely an underestimation largely because of the variability of definitions and classification of TBI across studies and databases. Epidemiological studies are usually based on hospital admission or discharge records, emergency department (ED) records, or death certificates and do not account for persons who did not seek medical attention, had outpatient evaluation, or those who received care at a federal facility (i.e., US military personnel or those seeking care at a Veterans Affairs hospital).

Incidence and trends of traumatic brain injury

Data from the CDC in 2014 estimated that approximately 2.87 million TBI-related ED visits, hospitalizations, and deaths occurred in the United States.

Of the 2.87 million cases reported ^, :

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  Approximately 288,000 were hospitalized and discharged

  
  
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  56,800 had TBI-related deaths, making up one-third of all injury-related deaths

Total combined rates for TBI-related ED visits from 2006 to 2014 have increased by 53%, while hospitalizations have decreased by about 8%, and deaths have decreased by 6% from 2006 to 2014. The number of ED visits was highest for children 0 to 4 years of age and for persons 75 years of age and older. ^,

Causes of traumatic brain injury

Overall leading causes of TBI in 2014 based on CDC reports: ^,

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  Falls were the overall leading cause of TBI, accounting for almost half (48%) of all TBI-related ED visits.

  
  
  
  
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    Falls disproportionately affect children and adults ages 75 and older.

    
    
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    Falls caused 49% of all TBI-related ED visits among children ages 0 to 17 years and 81% of all TBI-related ED visits among adults ages 75 and older

  
  
  
  
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  Being struck by or against an object was the second leading cause of TBI-related ED visits. ^,

  
  
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  Falls were the leading cause of TBI-related hospitalizations (52%), and motor vehicle accidents (MVA) were the second leading cause of TBI-related hospitalizations (20%). ^,

Traumatic brain injury–related death

During 2014, surveillance data from the CDC showed that there were approximately 56,800 TBI-related deaths each year. The first overall leading cause of all TBI-related deaths in 2014 was intentional self-harm. Falls and MVA were the second and third most common causes of overall TBI-related deaths respectively. Further data on overall rates of TBI-related deaths by mechanism of injury can be found in Fig. 6.1 from the CDC.

Rates of traumatic brain injury-Related Deaths by Mechanism of Injury, 2006–2014.

(From Centers for Disease Control and Prevention. National Vital Statistics System. Traumatic Brain Injury and Concussion. Available from https://www.cdc.gov/traumaticbraininjury/data/tbi-deaths.html .)

TBI-related deaths varied by age group :

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  Homicide was the leading cause of death for children ages 0 to 4 years.

  
  
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  MVAs were the leading cause of death for persons 15 to 24, 25 to 34, and adults ages 75 years or older.

  
  
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  Intentional self-harm was the leading cause of death for persons 45 to 64 years of age.

  
  
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  Falls were the leading cause of death for persons 65 years of age or older.

Risk factors and characteristics

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  TBI morbidity and mortality more common in males than females across all age groups. ^,

  
  
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  Children ages 0 to 4 years, older adolescents ages 15 to 19 years, and adults ages 65 years and older are most likely to sustain a TBI.

  
  
  
  
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    Different anatomical characteristics increase their risk of a TBI in the pediatric population. Children have larger and heavier heads relative to their bodies compared with adults. Additionally, their neck musculature and ligaments are weaker, making them more susceptible to injury. The disproportionate head weight in a child affects the movement of the head during a fall or external blow. ^,

  
  
  
  
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  Adults over the age of 75 years have the highest rates of TBI-related hospitalization and mortality. ^,

  
  
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  25% to 50% of all patients with acute TBI were intoxicated at the time of injury.

Sports and recreational injury

The majority of TBIs resulting from recreational and sporting activities are classified as concussions. According to data from the National Electronic Injury Surveillance System (NEISS), from 2001 to 2012, the rate of ED visits for sports and recreation-related injuries that included a diagnosis of concussion or TBI more than doubled among children aged 19 years and younger.

Sports with the highest incidence of concussion, in decreasing order, are American football, hockey, rugby, soccer, and basketball. ^, In sports with similar playing rules, the reported incidence of concussion is higher in female versus male athletes.

In American football, the most common mechanism of injury was player-to-player contact. Studies of professional players show that quarterbacks, wide receivers, running backs, and defensive backs have a three times greater risk of concussion versus linemen. Among high school football players, linemen and running backs were more likely to incur concussions. ^,

Military personnel

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  TBI is the signature injury from the Iraq and Afghanistan wars.

  
  
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  From 2000 to the first quarter of 2010, a total of 202,281 US service members were diagnosed with TBIs, and the number of TBIs diagnosed steadily increased during that decade.

  
  
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  Majority of cases are mild TBI. ^,

Economic cost

A CDC report estimated the economic burden of TBI in the United States to be about $56 billion, with mild TBI making up $16.7 billion of that amount.

Disability

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  Data from two states estimate that 3.2 million to 5.3 million persons in the United States are living with a TBI-related disability.

  
  
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  Outcomes at 5 years postinjury based on data from TBI Model Systems ^{, ,} :

  
  
  
  
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    57% are moderately or severely disabled.

    
    
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    55% do not have a job (but were employed at the time of their injury).

    
    
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    50% return to a hospital at least once.

    
    
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    33% rely on others for help with everyday activities.

    
    
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    29% are not satisfied with life.

    
    
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    29% use illicit drugs or misuse alcohol.

    
    
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    12% reside in nursing homes or other institutions.

  
  

Fall prevention

More than one-half of TBIs result from falls and are most common in children ages 0 to 17 and in patients ages 75 years or older.

Preventive measures aimed at various contributing factors based on patient age include: ^{( )}

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  Safety devices aimed at preventing falls from windows in pediatric population

  
  
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  Use of protective surfaces and safe borders of soft material (e.g., wood chips, sand, or rubber) in playgrounds

  
  
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  Balance therapy for postural control and fall prevention in older patients

  
  
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  Reduction of polypharmacy in elderly patients

  
  
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  Home modifications for elderly patients (e.g., brighter lighting, removal or repair of tripping hazards, grab bar installation).

Sports and recreational injury prevention

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  Bike helmets have been estimated to reduce head, brain, and severe brain injury in all age groups by nearly 70%.

  
  
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  Prevention measures for American football include helmet design upgrades, limiting the number of players on the field, and eliminating the three-point stance, and the National Football League (NFL) has passed rules limiting head-to-head contact.

Motor vehicle and motorcycle accident prevention

The National Highway Traffic Safety Administration (NHTSA) reports seat belt use reduces the risk of death by 45% and serious injury by 50% for drivers and front seat passengers in all causes of MVAs. The correct use of car seats, booster seats, and seat belts reduces the risk of serious and fatal injuries in children and adults. ^{, , ,}

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  Car seat use reduces the risk for injury in a crash by 71% to 82% for children compared with seat belt use alone. ^,

  
  
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  Booster seat use reduces the risk for serious injury by 45% for children ages 4 to 8 years compared with seat belt use alone. ^,

  
  
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  Seat belt use reduces the risk for death and serious injury by approximately half and by about 83% when used in combination with front-impact air bag protection compared with unrestrained drivers. ^,

Motorcycle crash deaths are preventable. The single most effective way to reduce mortality is helmet use.

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  In 2016, helmets saved an estimated 1859 lives.

  
  
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  In 2016, helmets could have prevented 802 deaths.

  
  
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  Helmets reduce the risk of death by 37%.

  
  
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  Helmets reduce the risk of head injury by 69%.