The brain is well protected inside the bony encasement of the skull, cushioned by a surrounding layer of spinal fluid. But sufficient force can cause damage to delicate brain tissue, and even minor injury can result in impairment of cognitive function and disturbance or mood and behavior. The most common causes of traumatic brain injury (TBI) are falls, car accidents, collisions and assault (http://www.cdc.gov/traumaticbraininjury/causes.html). This does not include military personnel who suffer TBI in blasts. Depending on the force of the impact, there may or may not be a loss of consciousness. In a mild injury, this may last seconds or minutes, whereas in a more serious injury a prolonged loss of consciousness, known as a coma, lasting weeks or months, usually indicates significant damage to brain tissue. A person may be conscious (awake) and still have disturbed consciousness – meaning that their brain is injured and not working properly. They may seem confused or extremely angry, which is also evidence of brain injury, and may not remember what happens during this time.
Significant brain injury can occur even when the person does not actually hit their head against anything, as in the “whiplash” injury sustained in a car accident, when the forces can cause a twisting of brain tissue, resulting in “micro-tears,” swelling and inflammation that may not be visible on a brain scan. Even in cases of relatively mild head injury, or concussion, with brief or no loss of consciousness, a person may experience symptoms of brain injury for days, weeks or months. Dizziness, nausea and headache may be worst for the first few days. Headaches can persist, along with fatigue, irritability, and poor concentration.
Some head injuries result in skull fracture, with the risk that the bones become displaced, pushing into and causing injury to the brain. (However, the brain injury is not necessarily more severe with a skull fracture, as the skull may have absorbed some of the impact.)
Head injury can result in bleeding (hematoma or hemorrhage) and swelling (edema) of the brain tissue. Both are big problems (unlike bleeding and swelling elsewhere) because space is limited inside the rigid skull, and the accumulation of blood and fluid can cause the brain tissue to be compressed – like people in an overcrowded elevator – causing more damage. If the parts of the brain controlling breathing and heart rate are damaged, this can be fatal. Serious head injuries are often treated with medications that control the swelling, and, if necessary, surgery is performed to remove the accumulated blood, or to temporarily remove a piece of the skull to relieve pressure on the brain.
Mild head injury may not be detected initially. Some people do not realize that they have suffered a head injury until weeks or even months later, when their physical injuries are healed and they return to their job or to school, and discover that they are having trouble doing their work, or that they are otherwise not themselves. Sometimes they are unaware of the changes, which may be observed by family, friends or coworkers.
In more severe brain injury, following coma, there are often significant problems with major brain functions, such as movement and speech. Irritability and mood instability are common, as are poor concentration and decreased initiative. Neuropsychological assessment is important to determine the nature and extent of cognitive (intellectual) and affective (emotional) difficulties. A program of rehabilitation, which may include physical therapy, speech therapy, occupational therapy and cognitive remediation, is done in the hospital or as an outpatient, ideally with family members involved.
TBI can result in one or more of three kinds of injury: structural – damage to brain cells; chemical – disruption of neurotransmitters and other chemicals essential for information processing; and psychological – emotional trauma that disrupts the person’s sense of safety and identity. Structural damage will interfere with whichever functions are controlled by that area of the brain, such as speech, gait, reasoning, or emotional control. Rehabilitation is extremely important, to retrain the brain as much as possible, and as brain tissue heals slowly, it can take up to two years to obtain optimal improvement.
Chemical (neurotransmitter) imbalances, resulting from inflammation of brain tissue, tend to interfere with Executive (control) and Affective (emotional) processes, resulting in impulsivity, irritability, or depression. These sometimes resolve with time, but require treatment with medication. The psychological trauma resulting from TBI or the event that caused it can affect a person in profound and unexpected ways, and are very important to address. It can interfere with a person’s “defense mechanisms,” leaving them feeling emotionally unsettled and vulnerable (see post traumatic stress disorder or PTSD).