Description

• Traumatic brain injury (TBI) is caused by external trauma to the brain and may result in chronic impairment of physical, cognitive, and psychosocial function.
• The management of acute TBI is not covered here.
• Mild TBI (mTBI) is synonymous with concussion.

Epidemiology

• Predominant age: highest incidence in three age groups: 75+ years >0 to 4 years >15 to 24 years
• Male > female (1.2:1)

Incidence

• ~2.5 million per year in the United States (likely an underestimate of disease burden because many do not seek medical care)
• 56,000 deaths per year (30% of all injury related deaths)

Prevalence
1–2% of the United States population has long-term TBI-related disabilities.

Pediatric Considerations

• Novel psychiatric disorders (NPD) post-TBI in children include, among others, secondary attention-deficit/hyperactivity disorder > conduct disorder > personality change > depressive disorder > anxiety disorder
• NPDs occur in as many as 31% of children with mTBI 2 years after injury.
• Predictors of a child developing NPDs include severity of injury, lower socioeconomic status, and degree of family dysfunction.

Etiology and Pathophysiology

• Most common causes: falls > object strike to the head > motor-vehicle crashes
• Intentional self-harm and violence-related TBI have increased.
• Sports and recreation injuries (especially in teenagers and young adults)
• Primary injury
  • Transfer of external forces to contents within the skull
  • Result in varying degrees and combinations of cortical contusions, coup-countercoup injury, hemorrhage (both axial and extra-axial), and stretching/sheering/transecting axonal injury
• Secondary injury
  • Cascade of molecular injury after primary injury resulting in ischemia and/or infarction of neuronal tissue
  • Secondary injury can continue well after the primary injury (hours to days after initial insult).
  • Mechanisms include release of excitatory neurotransmitters, release of free radicles, mitochondrial dysfunction, and ischemia from vasospasm among others.
  • Impaired axonal transport and inflammation lead to increased edema, raising intracranial pressure. This, in turn, reduces blood flow to brain and results in further ischemia/infarction.
  • Secondary injury can be made even worse with prior anticoagulation, subsequent hypoxia, and/or subsequent hypotension after primary injury.

Risk Factors

• Sex: male
• Age: 75+ years >0 to 4 years >15 to 24 years
• Lower socioeconomic status
• Alcohol and drug use
• Psychiatric disorders
• Military personnel/veterans

General Prevention

• Improved safety standards and programs to minimize injury from vehicular-related events (motor vehicle, motorcycle, bicycle, pedestrian), falls, violence, sports, and recreation provide best prevention against TBI.
• This includes car seat safety, seatbelt use, helmet use, trip hazards (senior living), balance activities (seniors), safety gates, sport-specific training, and playground safety regulations.

Commonly Associated Conditions

• Pain: chronic pain, chronic headaches
• Psychiatric: psychosis, depression, posttraumatic stress disorder, attention deficit disorder, suicidality
• Substance abuse