Classification and Complications of Traumatic Brain Injury

Epidemiology

Traumatic brain injury (TBI), also known as acquired brain injury, head injury, or brain injury, causes substantial disability and mortality. It occurs when a sudden trauma damages the brain and disrupts normal brain function. TBI may have profound physical, psychological, cognitive, emotional, and social effects. The diagnosis of mild TBI appears to be vastly underdiagnosed in the setting of systemic trauma, even in trauma centers.^[1]
According to the Center for Disease Control and Prevention's National Center for Injury Prevention and Control, the following annual statistics apply in the United States^[2] :

• At least 1.4 million people sustain a TBI.
• Approximately 50,000 people die from a TBI.
• Approximately 475,000 TBIs occur among infants, children, and adolescents aged 0-14 years.
• About 80,000-90,000 people experience the onset of a long-term disability due to a TBI.

The following groups are at particular risk for TBI^[2] :

• Males are about twice as likely as females to sustain a TBI.
• Infants and children aged 0-4 and adolescents aged 15-19 years are the 2 age groups at highest risk for a TBI.
• Adults aged 75 years or older have the highest rates of TBI-related hospitalization and death.

A TBI is caused by an excessive force, blow, or penetrating injury to the head. The leading causes of TBI are as follows^[2] :

• Falls (28%)
• Motor vehicle crashes (20%)
• Being struck by or against objects (19%)
• Assaults (11%)

Mortality rates after brain injury are highest in people with a severe TBI. In the first year after a TBI, people who survive are more likely to die from seizures, septicemia, pneumonia, digestive conditions, and all external causes of injury than are other people of similar age, sex, and race.^[3] However, the mortality rate after severe TBI has decreased since the late 20th century.^[4]
In one study, researchers estimated that the economic burden of TBI in the United States was approximately $37.8 billion in 1985.^[5] This estimate included $4.5 billion in direct expenditures for hospital care, extended care, and other medical care and services; $20.6 billion in work-related losses and disability; and $12.7 billion in lost income from premature death.