Causes and effects of traumatic brain injury (TBI)

Traumatic brain injury can happen when a sudden, violent blow or jolt to the head results in damage to the brain. In the United States and elsewhere, it is a major cause of disability and death.

As the brain collides with the inside of the skull, there may be bruising of the brain, tearing of nerve fibers and bleeding. If the skull fractures, a broken piece of skull may penetrate the brain tissue.

Causes include falls, sports injuries, gunshot wounds, physical aggression, and road traffic accidents.

The Centers for Disease Control and Prevention (CDC) define a TBI as “a disruption in the normal function of the brain that can be caused by a bump, blow, or jolt to the head, or penetrating head injury.”

The severity of symptoms will depend on which part of the brain is affected, whether it is in a specific location or over a widespread area, and the extent of the damage.

In mild cases, temporary confusion and headache may occur. Serious TBI can result in unconsciousness, amnesia, disability, coma, and death or long-term impairment.

The CDC estimated that, in 2013, TBI contributed to the deaths of some 50,000people. In 2012, 329,290 people aged under 19 years sought emergency treatment for a TBI resulting from a sporting or recreational activity.

Parents, guardians, and teachers should ensure that children are properly supervised and that they wear appropriate safety equipment during sporting and other activities.

A head injury or suspected TBI needs medical attention.

Fast facts on traumatic brain injury

  • The effect of a TBI, such as concussion, depends on the severity of the injury and where it occurs.
  • It is a major cause of death and disability in the United States and worldwide.
  • Causes include falls, road traffic accidents, and sports injuries.
  • Symptoms include confusion, persistent headaches, convulsions, and memory loss.
  • Anyone who receives a head injury, however mild, should consider seeking medical attention.

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A head injury can lead to cognitive impairment.

Signs and symptoms may appear at once, within 24 hours, or they may emerge days or weeks after the injury. Sometimes the symptoms are subtle. A person may notice a problem but not relate it to the injury. Some people will appear to have no symptoms after a TBI, but their condition worsens later.

The effects can be physical and psychological.

The initial physical effects include bruising and swelling. Increased pressure in the brain can cause:

  • damage to brain tissue, as it presses against the skull or as one part of the brain pushes into another
  • pressure on blood vessels, reducing their ability to supply the brain cells with oxygen and essential nutrients

Internal bleeding

Signs of internal bleeding include bruising behind the ears (battle sign) or around the eyes (raccoon eyes). These can potentially indicate a severe or life-threatening injury. They need immediate medical attention.

Other signs that may indicate severe injury include:

  • a loss of consciousness
  • convulsions or seizures
  • repeated vomiting
  • slurred speech
  • weakness or numbness in the arms, legs, hands, or feet
  • agitation
  • loss of coordination
  • dilated pupils
  • inability to wake up from sleep
  • severe headache
  • weakness and numbness in hands, feet, arms or legs

The following signs and symptoms can also indicate a need for urgent attention:

  • confusion
  • changes in mood
  • memory problems
  • inability to remember what happened before or after the incident
  • fatigue (tiredness) and lethargy
  • getting lost easily
  • persistent headaches
  • persistent pain in the neck
  • slowness in thinking, speaking, reading or acting
  • moodiness, for example, suddenly feeling sad or angry for no apparent reason
  • sleep pattern changes, such as sleeping more or less than usual, or having trouble sleeping
  • lightheadedness, dizziness
  • becoming more easily distracted
  • increased sensitivity to light or sounds
  • loss of sense of smell or taste
  • nausea
  • tinnitus, or ringing in the ears

These may appear at once, within hours, or later. A person who has received a TBI but who appears to have no symptoms should be closely monitored for 24 hours, as signs of injury may not be immediate.

Anyone who experiences the above symptoms even days or weeks after a TBI should see a doctor.

A child with a TBI may become irritable and listless.

Children will have the same signs and symptoms, but they may be less likely to let others know how they feel.

If an infant has received a blow or jolt to the head and any of the following signs or symptoms occur, call a doctor:

  • changes in sleeping patterns
  • irritability and crying
  • listlessness
  • loss of balance
  • loss of newly acquired skills, such as toilet training
  • changes in playing behavior changes
  • refusal to eat
  • loss of interest in favorite activities or toys
  • tiredness
  • unsteady walking
  • vomiting

If these signs are noticed, the child should see a doctor.

In sport, the participant should leave out the game and not play again until the doctor gives permission to return, whether or not they lose consciousness. Not every TBI or concussion involves a loss of consciousness.

Repeated head injuries in rapid succession can be particularly harmful to the brain in the long term.

It is important to monitor a person who has had a TBI because their condition can deteriorate rapidly and symptoms that appear mild can become severe.

Long-term effects

There is growing evidence that a TBI or repeated TBIs can have long-term effects on health, including an increased risk of dementia and other neurological and neurodegenerative disorders. Football players with high scores on tests for depression have also been found to have a larger number of concussions.

Tips for recovery

Tips that can aid recovery:

  • Avoid activities that could cause another blow or jolt to the head.
  • Follow the instructions of healthcare professionals.
  • Do not take drugs that the physician has not approved.
  • Do not return to normal activities, including driving and sports participation, until the doctor agrees.
  • Get plenty of rest.

It is important to follow the doctor’s instructions after a TBI, because the impact of a brain injury can be severe, and it is not always immediately apparent.

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Some tips can reduce the risk of a TBI.

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Never drink and drive.

  • Always use a seat belt when driving or traveling in a car
  • Children should use a suitable restraint for their age and size
  • Never drive after drinking alcohol
  • Use a helmet when playing sports or using a vehicle where an incident could involve a head injury
  • Instal grab bars in a bathroom that is used by older people
  • Use non slip mats on floors that can get wet
  • Remove trip hazards, such as loose carpets and trailing wires
  • Install window guards and safety gates on stairs if there are children around
  • Ensure that play areas are made of a shock-absorbing surface, such as wood mulch
  • Store any firearms, unloaded, in a locked safe or cabinet, and keep the bullets in a different location

Special care should be taken when supervising young children or older adults. Household adaptations, such as ramps and window guards, may be necessary.

The American Academy of Family Physicians recommends that everyone should go to a doctor after a blow to the head. If someone else hits their head and is behaving in an unusual way, the person who notices it should contact a doctor.