Breathing, blood flow, and movement are all controlled by the brain. The brain also allows you to think, handle emotions, and make judgments. TBI can be due to a closed head injury or a penetrating injury. The most common causes are falls, blunt accidental trauma, motor vehicle accidents and assault. After an injury, certain parts of the brain (or the links between these parts) may not be working optimally. Some mental or physical skills may be altered. The altered function may be short- or long-term. The full effects of a brain injury may not appear for months or even years and typically depends on the severity and the number of brain injuries as well as the time in between these injuries. Long-term effects, initially not present, include post-traumatic stress disorder and cognitive decline (early dementia). TBI can range from mild concussions to fatal injuries.
The skull does not have to be harmed for the brain to be injured (this is called a closed head injury). Injury can occur when the brain strikes the skull. In many cases, the brain rebounds from the first impact and hits the opposite side of the skull. Sometimes the brain twists on the brain stem.
When the brain strikes the skull or twists on the brain stem, brain tissue tears. This injury may then cause a second type of damage, such as bleeding or swelling in the brain. Health care providers try to control the second type of damage to help limit long-term problems.
If nerve fibers in the brain tissue tear, signals can’t pass between the brain and body. Lost signals mean altered skills or body functions.
A torn blood vessel may leak into nearby tissue. This kills brain cells and can lead to a buildup of blood (hematoma). If this blood presses on the brain, it can cut off blood to other cells. These cells also die.
The brain has almost no room to expand inside the skull. If the brain swells, it may press against the skull. As the pressure increases, the brain functions may be altered.