Causes of TBI and Concussion

Causes of Traumatic Brain Injury and Concussion

Our skull serves as the first line of defense for our brain. Although the bones of the skull protect us from objects that might penetrate our brain, it does little to protect the brain from the force of a blow to the head. Instead, cerebrospinal fluid surrounds our brain inside of the skull. This fluid keeps our brain “floating” inside of our skull cavity so that the brain does not hit the inside walls of the skull.

A traumatic brain injury (TBI) occurs when the skull and cerebrospinal fluid are unable to protect the brain from an incoming force, such as when you hit your head. When you experience a forceful blow or violent shaking of the head, your brain bumps into the inside of your skull. This contact with the inner skull can tear blood vessels, injure nerve fibers, and bruise brain tissue (also known as a contusion). These contusions can cause the brain tissue to bleed and swell, which in turn can put pressure on surrounding blood vessels and decrease the flow of blood to the brain.

Recent estimates published by the U.S. National Institutes of Health (2017) show disturbingly high prevalence rates of TBI in the United States. An estimated 2.8 million Americans are experiencing TBI each year. Broken down, this statistic translates to approximately 2.5 million TBI-related emergency room visits, nearly 300,000 TBI-related hospitalizations, and 56,000 TBI-related deaths per year. These numbers have gathered the attention of the Center for Disease Control and Prevention, who list TBIs as a major cause of death and disability in the United States.

Although there are many ways to get a TBI, the three main causes of TBI in the United States are falls, being struck by or against an object, and motor vehicle crashes.

Falls & Traumatic Brain Injuries

Falls account for nearly 50% of all TBI-related emergency room visits, hospitalizations, and deaths in the United States. Because we are more likely to fall at certain stages of development, falls linked with TBI are more likely to occur when we are younger (i.e., age 0-14 years) or when we are older (i.e., 44+ years). For the younger population, 54% of all TBI-related emergency room visits, hospitalizations, and deaths were a result of falls. Older Americans have a much higher percentage of TBI-related emergency room visits, and deaths related to falls, with falls accounting for nearly 75% of these injuries.

Being Struck by or Against an Object

Being struck by or against an object is the second most likely cause of TBI in the United States and is especially common in adolescents and young adults between the ages of 15-24. Often times, this blunt force trauma is the result of participation in athletics, especially contact sports such as American football, hockey, and basketball. Unsurprisingly, major sports agencies, such as the NCAA, have been especially aware of how athletes are more prone to receive a TBI-related injury as a result of their sport. This cause of injury is not limited to sports, though. In 2013, approximately 233,000 Americans indicated that their TBI was related to an assault, and assault was the leading cause of TBI-related death in children ages 0-4 years. Recent trends have indicated a growing number of TBIs are related to self-injury, in which a person purposely hits their head either with or against an object.

Motor Vehicle Crashes Resulting in Traumatic Brain Injuries

Motor vehicle crashes are the most common cause of TBI in Americans between the ages of 14 and 44, accounting for nearly 20% of all TBI-related deaths. It is important to note that motor vehicle crashes can cause TBI in two different ways: (1) direct impact to the head (i.e., hitting your head on the steering wheel) or (2) whiplash. With whiplash, nothing has to come into physical contact with the head. Instead, whiplash occurs when the head is shaken violently enough that the fluid surrounding the brain is not able to protect it from hitting the inside of the skull, thus resulting in a TBI.

Although this list is far from conclusive, falls, being struck by or against something, and motor vehicle crashes are the three major causes of TBI in the United States. No matter what event caused the injury, the root problem in TBI and concussion is that the skull and the cerebrospinal fluid are unable to buffer against extreme changes in physical momentum, causing the brain to bounce off of the inside of the skull.

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