Brain scan. Causes of traumatic brain injury.

What Causes Traumatic Brain Injury

Traumatic brain injury (TBI) refers to injury to the brain as a result of external forces. This might refer to a direct blow to the skull, a change in direction or movement (such as whiplash), or when the brain injures itself from moving around inside the skull (from the force of a blow). There are many types of TBI and each have a range of causes. Here’s a look at some of the causes of traumatic brain injury. 

Open Brain Injury

An open or penetrating brain injury refers to injuries that “penetrate” the skull. These injuries pass through the external skin and bone and directly damage the brain tissue. Rather than widespread damage, penetrating TBI tends to cause localized damage and the resulting disabilities are easier to foresee. 

Common causes of penetrating brain injuries include knives or bullet wounds. Almost all (91%) bullet wound related brain injuries result in death. If the object (i.e. a bullet) that penetrates the skull isn’t going fast enough to exit on the other side of the head, it can actually ricochet off the other side of the skull and cause even more damage. 

Conversely, “through and through” injuries are those that go in one side of the brain and out the other. Phineas Gage, a railroad worker in the mid-1800s, is perhaps the most famous example of this form of injury. A railroad tie entered Gage’s cheek, went up through his brain, and out the other side of his skull; the injury resulted in permanent damage, but was not fatal. Any object sharp enough or moving fast enough to penetrate the skull is considered an open brain injury. 

Closed Brain Injury

Closed TBI refers to injuries that occur strictly from outside, damaging the brain through its thick layer of boney protection without penetrating it. Concussions, cerebral contusions, and subdural hematomas are generally closed brain injuries, most often caused by blunt force trauma to the head. This type of injury can also include coup-contrecoup injuries, in which the traumatic force is so strong it causes injury at the site of impact as well as the opposite side of the brain.

Automobile accidents (from hitting your head on a windshield or being hit by a car), receiving a blow from a player or equipment in a sporting game, getting in a fight or being assaulted, or suffering a fall are all common causes of closed brain injuries. Some of these incidents, of course, could also result in open brain injuries, depending on the circumstances. As such, car accidents, sports related injuries, and combat related injuries are the most common causes of TBI. 

Movement Related TBI

TBI can result from whiplash-like injuries, when the head is moving swiftly in one direction and something causes an abrupt change in direction or movement, which tears the connecting structures. These are often categorized as “diffuse axonal injuries,”  The Brain Injury Association of American states that diffuse axonal injuries are usually the result of “shaking…, strong rotation of the head…, or by rotational forces.” Car accidents are common causes of this type of injury. 

Additionally, shaken baby syndrome is an example of the result of a diffuse axonal injury. Because of the delicate structure of infants, being shaken can cause their heads to move too swiftly for their brains to move in tandem.

Repeated Injury

Second impact syndrome is a type of recurrent TBI. Either injury can be any type of TBI, but because of the repetitive brain injury the second injury tends to be much more severe and more likely to be fatal, as a result of the brain’s inability to heal before repeated injury. 

Last Updated: April 05, 2017