The Causes of Traumatic Brain Injury

The Centers for Disease Control and Prevention (CDC) had estimated that there are 1.5 million people in the United States alone that suffer a traumatic brain injury (TBI) each year. Of these 1.5 million people, 50,000 people die and 85,000 suffer from long-term disabilities. The CDC also estimates that more than 5.3 million people with disabilities lives that were caused by traumatic brain injuries.

There are, without a doubt, many, varied causes of these brain injuries. The top three causes are vehicle crashes, firearms, and falls. Firearm injuries are often fatal. Of those that are injured due to a firearm, 90% die. Young adults and the elderly are the most at risk for this type of injury.

There are a few situations that result in traumatic brain injuries. These are called the mechanisms of injury. The main mechanisms of injury are open head injury, closed head injury, deceleration injuries, chemical and toxic injuries, and hypoxia.

Open head injuries are frequently bullet wounds. They involve some sort of object such as a bullet ,a nail, etc. penetrating the skull. Generally, this type of wound has mainly focal damage, or damage that is confined to a small area of the brain. Despite this, the effects of the injury can be as serious as closed brain injuries.

Closed head injuries generally result falls or car crashes. They can involve focal damage as well as widespread damage to axons (tiny portions of nerves inside the brain). The closed head injuries effects are frequently broad and diffuse. In order for an injury to be closed head injury, there cannot have been penetration of the skull into the brain cavity.

Deceleration injuries are often known as diffuse axonal injuries. This type of injury is due to the physics of the brain than anything else. The skull is hard and inflexible while the brain is soft with the consistency of jello. When the skull decelerates rapidly due to contact with a stationary object, the brain moves around inside the skull. The brain moves at a different rate than the skull because it is soft. In addition, various 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 truck leads to direct brain injury. The brain injury is due to diffuse axonal shearing, contusion, and brain swelling. Diffuse axonal shearing is the compression and stretching of the axons and neurons due to the gelatinous consistency. This movement causes the fragile axons to be stretched and compressed. They frequently stretch until they are torn (shearing). When the axons are sheared, the neurons die.

Toxic or chemical traumatic brain injuries are frequently due to metabolic disorders. They occur when harmful chemicals damage the neurons.

Hypoxia, or the lack of oxygen, is also a major source of traumatic brain injury. When the blood flow to the brain is depleted of oxygen, either or completely or in reduced quantities, brain damage occurs. This brain damage can occur if the brain is left without oxygen for merely a few minutes. The lack of oxygen can be caused by heart attacks, respiratory failure, a decrease in blood pressure, and a low oxygen environment. Hypoxia can result in severe cognitive and memory defects.