Traumatic brain injury (TBI), also called “acquired brain injury” or simply “head injury,” occurs when a sudden trauma causes damage to the brain. Most people are unaware of the scope of TBI or its overwhelming nature, and it may be missed initially when medical personnel are focused on saving the individual’s life. Although medical technology has advanced greatly over the last several years, the effects of TBI are significant.
Causes of traumatic brain injury include the following:
Open Head Injury: There is penetration of the skull resulting from bullet wounds or other sharp objects, for example. The damage is largely focal, and generally the effects are extremely serious.
Closed Head Injury: There is no penetration of the skull and usually results from blast (concussive) injuries, falls, motor vehicle accidents, etc. There is focal damage, as well as damage to large axons of the neurons (single nerve cells) in the brain and/or spinal chord, and the effects tend to be diffuse (broad).
Deceleration Injuries (Diffuse Axonal Injury): The skull is hard and inflexible while the brain is soft with the consistency of gelatin. The movement of the skull through space (acceleration) and the rapid discontinuation of this action when the skull meets a stationary object (deceleration) cause the brain to move inside the skull. The brain moves at a different rate than the skull, because it is soft. Different parts of the brain move at different speeds because of their relative weights. The differential movement of the skull and the brain when the head is struck results in direct brain injury, due to diffuse axonal shearing, contusion, and brain swelling. Therefore, when the brain is slammed back and forth inside the skull, it is alternately compressed and stretched because of the gelatinous consistency. The long, fragile axons of the neurons (single nerve cells) in the brain and spinal cord are also compressed and stretched. If the impact is strong enough, axons can be stretched until they are torn. This is called axonal shearing. When this happens, the neuron dies. After a severe brain injury, there is massive axonal shearing and neuron death.
Chemical/Toxic Injuries: This occurs when harmful chemicals, such as insecticides, solvents, carbon monoxide poisoning, and lead poisoning, damage the neurons.
Anoxia (lack of oxygen) or Hypoxia (reduced oxygen): If blood flow to the brain is affected negatively, then irreversible brain injury can occur from anoxia (no oxygen) or hypoxia (reduced oxygen). It may take only a few minutes for this to occur. This condition may result from heart attacks, respiratory failure, drops in blood pressure, and a low oxygen environment. This type of brain injury can result in severe cognitive and memory deficits.
Tumors: Tumors caused by cancer, for example, can grow on or over the brain and can cause brain injury by invading the spaces of the brain and causing direct damage. Damage can also result from pressure effects around an enlarged tumor, and surgical procedures to remove the tumor may also contribute to the brain injury.
Infections: The brain and surrounding membranes are very prone to infections if the special blood-brain protective system is breached. Viruses and bacteria can cause serious and life-threatening diseases of the brain (encephalitis and meningitis).
Stroke: If blood flow to the brain is blocked through a cerebral vascular accident (stroke), cell death in the area deprived of blood will result. If there is bleeding in (hemorrhage) or over (hematoma) the brain because of a tear in an artery or vein, loss of blood flow and injury to the brain tissue by the blood will also result in brain damage.
Although the diagnoses of TBI are still imprecise, TBI is classified into three categories: mild, moderate, and severe.
Mild: Brain injury can be classified as mild if loss of consciousness and/or confusion and disorientation is shorter than 30 minutes. While MRI and CAT scans are often normal, the individual has cognitive problems such as headaches, difficulty thinking, memory problems, attention deficits, mood swings, and frustration. These injuries are commonly overlooked. A person with a mild TBI may remain conscious or may experience a loss of consciousness for a few seconds or minutes. Other symptoms of mild TBI include headache, confusion, lightheadedness, dizziness, blurred vision or tired eyes, ringing in the ears, bad taste in the mouth, fatigue or lethargy, a change in sleep patterns, behavioral or mood changes, and trouble with memory, concentration, attention, or thinking. Even though this type of TBI is called “mild,” the effect on the family and the injured person can be devastating.
Moderate: A person with a moderate or severe TBI may show the same symptoms as described above, but may also have a headache that gets worse or does not go away, repeated vomiting or nausea, convulsions or seizures, an inability to awaken from sleep, dilation of one or both pupils of the eyes, slurred speech, weakness or numbness in the extremities, loss of coordination, and increased confusion, restlessness, or agitation.
Severe: A severe brain injury is associated with loss of consciousness for more than 30 minutes and memory loss after the injury or penetrating skull injury longer than 24 hours. The deficits range from impairment of higher level cognitive functions to comatose states. Survivors may have limited function of arms or legs, abnormal speech or language, loss of thinking ability, or emotional problems. The range of injuries and degree of recovery is very variable and differs on an individual basis.
Anyone with signs of moderate or severe TBI should receive medical attention as soon as possible. Because little can be done to reverse the initial brain damage caused by trauma, medical personnel try to stabilize an individual with TBI and focus on preventing further injury. Primary concerns include insuring proper oxygen supply to the brain and the rest of the body, maintaining adequate blood flow, and controlling blood pressure. Imaging tests help in determining the diagnosis and prognosis of a TBI patient. Patients with mild to moderate injuries may receive skull and neck X-rays to check for bone fractures or spinal instability. For moderate to severe cases, the imaging test is a computed tomography (CT) scan. Moderately to severely injured patients should receive rehabilitation that involves individually tailored treatment programs in the areas of physical therapy, occupational therapy, speech/language therapy, physical medicine, psychology/psychiatry, and social support.
The effects of TBI can be profound. Individuals with severe injuries can be left in long-term unresponsive states. For many people with severe TBI, long-term rehabilitation is often necessary to maximize function and independence. Even with mild TBI, the consequences to a person’s life can be dramatic. Moderately to severely injured patients should receive rehabilitation that involves individually tailored treatment programs in the areas of physical therapy, occupational therapy, speech/language therapy, physical medicine, psychology/psychiatry, and social support. Changes in brain function can have a dramatic impact on family, job, social, and community interaction.