Common Causes of TBI

Traumatic brain injury is caused by a blow or other traumatic injury to the head.  The degree of damage can depend on several factors including the nature of the event and the force of impact.  Common events causing traumatic brain injury include the following:

• Falls (35.2%) – Falling out of bed, slipping in the bath, falling down steps, falling from ladders and related falls are the most common cause of traumatic brain injury overall, particularly in older adults and young children.
• Vehicle-related collisions (17.3%) – Collisions involving cars, motorcycles or bicycles — and pedestrians involved in such accidents — are a common cause of traumatic brain injury, particularly among adults in their early 20s.
• Violence (10%) – About 10 percent of traumatic brain injuries are caused by violence, such as gunshot wounds, domestic violence or child abuse. Shaken baby syndrome is traumatic brain injury caused by the violent shaking of an infant that damages brain cells.
• Sports injuries – Traumatic brain injuries may be caused by injuries from a number of sports, including boxing, football, baseball, lacrosse, skateboarding, hockey, and other high-impact or extreme sports.
• Explosive blasts and other combat injuries – Explosive blasts are a common cause of traumatic brain injury in active-duty military personnel. Although the mechanism of damage isn’t well understood, many researchers believe that the pressure wave passing through the brain significantly disrupts brain function. Traumatic brain injury also results from penetrating wounds, severe blows to the head with shrapnel or debris, and falls or bodily collisions with objects following a blast.

TBI is a major cause of death and disability worldwide, especially in children and young adults. The most common causes of TBI in the U.S. include violence, transportation accidents, construction, and sports.  Bicycles and motor bikes are major causes, with the latter increasing in frequency in developing countries. The estimates that between 1.6 and 3.8 million traumatic brain injuries each year are a result of sports and recreation activities in the US. In children aged two to four, falls are the most common cause of TBI, while in older children bicycle and auto accidents compete with falls for this position. TBI is the third most common injury to result from child abuse. Abuse causes 19% of cases of pediatric brain trauma, and the death rate is higher among these cases. Domestic violence is another cause of TBI, as are work-related and industrial accidents. Firearms and blast injuries from explosions are other causes of TBI, which is the leading cause of death and disability in war zones. According to Representative Bill Pascrell (Democrat, NJ), TBI is “the signature injury of the wars in Iraq and Afghanistan.”


Who is at Risk?

• Approximately 18% of all TBI-related emergency department visits involved children aged 0 to 4 years.
• Approximately 22% of all TBI-related hospitalizations involved adults aged 75 years and older.
• Males are more often diagnosed with a TBI (59%).

These mechanisms are the highest causes of brain injury: open head injury, closed head injury, deceleration injuries, chemical/toxic, hypoxia, tumors, infections and stroke.

Open Head Injury – Results from bullet wounds, largely focal damage, penetration of the skull, effects can be just as serious as closed brain injury.

Closed Head Injury – Resulting from a slip and fall or motor vehicle accident.  Focal damage and diffuse damage to axons, effects tend to be broad (diffuse), no penetration to the skull.

Deceleration Injuries – The skull is hard and inflexible while the brain is soft with the consistency of gelatin.  The brain is encased inside the skull.  During the movement of the skull through space (acceleration) and the rapid discontinuation of this action when the skull meets a stationary object (deceleration) causes the brain to move inside the skull.  The brain moves at a different rate than the skull because it is soft.  Different parts of the brain move at different speeds because of their relative lightness or heaviness.  The differential movement of the skull and the brain when the head is struck results in direct brain injury, due to diffuse axonal shearing, contusion and brain swelling.

Chemical/Toxic – Also known as metabolic disorders.  This occurs when harmful chemicals damage the neurons.  Chemicals and toxins can include insecticides, solvents, carbon monoxide poisoning, lead poisoning, etc.

Hypoxia (Lack of Oxygen) – If the blood flow is depleted of oxygen, then irreversible brain injury can occur from no oxygen or reduced oxygen.  This condition may be caused by heart attacks, respiratory failure, drops in blood pressure and a low oxygen environment.  It may only take a few minutes for this to occur.

Tumors – Tumors caused by cancer can grow on or over the brain.  Damage can also result from pressure effects around an enlarged tumor as well as surgical procedures to remove the tumor.

Infections – The brain and surrounding membranes are very prone to infections if the special blood brain protective system is breached.

Stroke – If blood flow is blocked through a cerebral vascular accident (stroke) cell death in the area deprived of blood will result.