Traumatic Brain Injury
What is Traumatic Brain Injury?
Traumatic brain injury, often referred to as TBI, is defined as any brain injury produced by an external force that disrupts the normal function of the brain. TBI can occur when the head suddenly and violently hits an object, causing the brain to collide with the inside of the skull, or when an object pierces the skull and enters brain tissue. Mild TBI (concussion) may cause temporary dysfunction of brain cells, whereas more serious TBI can result in bruising, torn tissues, bleeding and other physical damage to the brain that can result in long-term complications or death. In addition to the damage caused at the moment of injury, alterations in cerebral blood flow and pressure within the skull occur in the minutes and days following the injury. These pressure and blood flow changes are referred to as secondary injury, and they contribute substantially to the damage from the initial injury. The primary goal in the ICU is to prevent any secondary injury to the brain. Various neuro-monitoring devices assist the team in caring for the patient. Please see Neurocritical Care document for extensive information on devices used and treatment methods that take place in the neurocritical care unit.
TBI is a major cause of death and disability worldwide, especially in children and young adults. About 1.7 million cases of TBI occur in the United States every year. Causes include falls, vehicle accidents, and violence. Approximately 5.3 million people live with a disability caused by TBI in the United States alone.
Facts and Statistics about TBI
- Annual direct and indirect TBI costs are estimated at $48-$56 billion.
- There are about 235,000 hospitalizations for TBI every year, which is more than 20 times the number of hospitalizations for spinal cord injury.
- Among children ages 14 and younger, TBI accounts for an estimated 2,685 deaths, 37,000 hospitalizations, and 435,000 emergency room visits.
- Every year, 80,000-90,000 people experience the onset of long-term or lifelong disabilities associated with TBI.
- Males represent 78.8% of all reported TBI accidents, and females represent 21.2%.
- National statistics estimate between 50 and 70% of TBI accidents are the result of a motor vehicle accident.
- Sports and recreational activities contribute to about 21% of all traumatic brain injuries among American children and adolescents.
- The mortality rate for TBI is 30 per 100,000, or an estimated 50,000 deaths in the United States annually. Of those who die, 50% do so within the first two hours of their injury.
- Deaths from head injuries account for 34% of all traumatic deaths. Beginning at age 30, the mortality risk after head injury begins to increase. Persons age 60 and older have the highest death rate after TBI, primarily because of falls, which have a rising incidence in this age group.
Prevention measures include use of technology to protect those who are in accidents, as well as efforts to reduce the number of accidents, such as safety education programs and enforcement of traffic laws.
- Wear a seatbelt every time you drive or ride in a motor vehicle.
- Never drive while under the influence of drugs or alcohol or ride as a passenger with anybody else who is under the influence.
- Keep firearms unloaded in a locked cabinet or safe, and store ammunition in a separate, secure location.
- Remove hazards in the home that may contribute to falls. Secure rugs and loose electrical cords, put away toys, use safety gates, and install window guards. Install grab bars and handrails if you are frail or elderly.
- Buy and use helmets or protective head gear approved by the ASTM for specific sports 100 percent of the time.
- Supervise younger children at all times, and do not let them use sporting equipment or play sports unsuitable for their age. Do not let them use playgrounds with hard surface grounds.
- Follow all rules and warning signs at water parks, swimming pools, and public beaches.
- Do not dive in water less than 12 feet deep or in above-ground pools. Check the depth – and check for debris in the water before diving.
- Wear appropriate clothing for the sport.
- Do not wear any clothing that can interfere with your vision.
- Do not participate in sports when you are ill or very tired.
- Obey all traffic signals and be aware of drivers when cycling or skateboarding.
- Avoid uneven or unpaved surfaces when cycling, skateboarding, or in-line skating.
- Perform regular safety checks of sports fields, playgrounds and equipment.
- Discard and replace sporting equipment or protective gear that is damaged.
- Never slide head-first when stealing a base.
Classification of TBI
TBI is usually classified based on severity, anatomical features of the injury, and the mechanism (the causative forces). Mechanism-related classification divides TBI into closed and penetrating head injury. A closed (blunt) injury occurs when the brain is not exposed. A penetrating (open) head injury occurs when an object pierces the skull and breaches the dura mater (outermost membrane surrounding the brain.
Glasgow Coma Scale (GCS) is the most commonly used system for classifying TBI severity. This scale grades a person’s level of consciousness on a scale of 3-15 based on verbal, motor, and eye-opening reactions to stimuli. A TBI with a GCS of 13 or above is mild. These patients tend to do well in the recovery process. Patients with moderate TBI score between 9–12. For closed head injury, around 60% of these patients will make a positive recovery, and around 25% will be left with a moderate degree of disability. Death or a vegetative state will be the outcome in 7-10% of cases. The remainder of patients will have a severe disability. Patients with a score of 8 or below have severe TBI. For closed injury, only 25-33% of these patients have positive outcomes. About 33% of these patients do not survive, and the remaining patients remain in a vegetative state.
Outcomes for penetrating head injuries tend to follow a different pattern. Handguns are the most common cause of penetrating head injuries. More than 50% of all patients with gunshot wounds to the head who are alive upon arrival do not survive because their injuries are so severe. However, most of the remaining patients have relatively mild injuries, scoring between 13-15, and tend to do fairly well. Very few patients with gunshot wounds will have injuries of intermediate severity, but this group has the most varied outcomes.
Despite its usefulness, the GCS grading system has limited ability to predict outcomes, requiring additional classification systems to be used in order to determine severity. A current model developed by the Department of Defense and Department of Veterans Affairs uses all three criteria of GCS after resuscitation, duration of post-traumatic amnesia (PTA), and loss of consciousness (LOC). There are also grading scales available to classify the severity of mild TBI (concussion). There are classification systems available to further classify TBI by its pathological features.
Symptoms of a TBI can be mild, moderate, or severe, depending on the extent of damage to the brain. Mild cases may result in a brief change in mental state or consciousness. 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. Moderate or Severe cases may show similar symptoms, 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 of both pupils of the eyes, slurred speech, weakness or numbness in the extremities, loss of coordination, and increased confusion, restlessness, or agitation. Severe cases oftentimes result in extended periods of unconsciousness, coma, or even death.
Types of Injury
TBIs create areas of localized injury that may cause pressure within the brain. These are called mass lesions. The most common mass lesions in a TBI are hematomas and contusions. A hematoma is a blood clot within the brain or on its surface. Hematomas may occur anywhere in the brain. An epidural hematoma is a collection of blood between the dura mater and the inside of the skull. A subdural hematoma is a collection of blood between the dura mater and the arachnoid layer, which sits directly on the surface of the brain.
A cerebral contusion is bruising of brain tissue. They consist of areas of injured or swollen brain mixed with blood that has leaked out of arteries, veins, or capillaries. Contusions are seen most commonly at the base of the front parts of the brain, but they may occur anywhere.
Please see intracerebral hemorrhage section for more information on this type of TBI.
Subarachnoid hemorrhage (SAH) is caused by bleeding into the subarachnoid space. It appears as diffuse blood spread thinly over the surface of the brain, and is seen commonly after TBI. Most cases of SAH associated with head trauma are mild. Hydrocephalus may result from severe traumatic SAH. Please see Neurocritical Care section for more information on hydrocephalus.
TBI can produce microscopic changes that cannot be seen on CT scans and that are scattered throughout the brain. This category of injuries is called diffuse brain injury, which may occur with or without an associated mass lesion.
Diffuse axonal injury refers to impaired function and gradual loss of some axons, which are the long extensions of a nerve cell that enable such cells to communicate with each other even if they are located in parts of the brain that are far apart. If enough axons are injured in this way, then the ability of nerve cells to communicate with each other and to integrate their function may be lost or greatly impaired, possibly leaving a patient with severe disabilities.
Another type of diffuse injury is ischemia, or insufficient blood supply to certain parts of the brain. A decrease in blood supply to very low levels may occur commonly in a significant number of TBI patients. This is crucial because a brain that has just undergone a traumatic injury is very sensitive to even the slightest reductions in blood flow.
Linear skull fractures are simple breaks or “cracks” in the skull that (generally) do not require any treatment. Fractures of the base of the skull are problematic if they cause injury to nerves, arteries, or other structures. If a fracture extends into the sinuses, there may be leakage of cerebrospinal fluid (CSF) from the nose or ears. Most leaks will stop spontaneously. Sometimes, however, it may be necessary to insert a lumbar drain, which is a long, thin, flexible tube that is inserted into the CSF space in the spine of the lower back. This provides an alternate route for CSF drainage so that the dural tear that is responsible for the CSF leak in the base of the skull has time to seal.
Depressed skull fractures are where the skull (bone) presses on or into the brain. These may require surgical treatment. The damage caused by depressed skull fractures depends upon the region of the brain in which they are located and the possible coexistence of any associated diffuse brain injury.
Upon arrival to the hospital, patients with TBI need to undergo a systematic, yet rapid, evaluation in the emergency room. Cardiac and pulmonary function is assessed first. Next a quick body examination is performed, followed by a complete neurological examination, which is assessed using the GCS. The ability of the pupils to become smaller in bright light is also tested. In patients with large mass lesions or high intracranial pressure (ICP), one or both pupils may be very wide or “blown.” The presence of a blown pupil on only one side usually indicates a large mass on the same side as the dilated pupil. Brainstem reflexes, including gag and corneal (blink) may also be tested.
CT is the gold standard for the radiological assessment of a TBI patient. They are excellent tests for detecting the presence of blood and fractures, which are the most crucial lesions to identify in medical trauma cases. MRI is not commonly used for acute brain injury because it takes longer to perform MRI than CT scanning. After a patient has been stabilized, MRI may demonstrate the existence of lesions that were not detected on the CT scan. This information is generally more useful for determining prognosis than for influencing treatment.
Patients 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 (secondary) injury.
Approximately half of severe TBI patients will need surgery to remove or repair hematomas (ruptured blood vessels) or contusions (bruised brain tissue). Patients are sometimes taken directly from the emergency room to the operating room. In many cases, surgery is performed to remove a large hematoma or contusion that is significantly compressing the brain or raising the pressure within the skull. After surgery, these patients are observed and monitored in the neurointensive care unit.
Other TBI patients may not go to the operating room immediately, but instead are taken from the emergency room to the ICU. Contusions or hematomas may enlarge over the first hours or days after head injury, so some patients are not taken to surgery until several days after an injury. Delayed hematomas may be discovered when a patient’s neurological exam worsens or when their ICP increases. On other occasions, a follow-up CT scan that was ordered to determine if a small lesion has changed in size indicates that the hematoma or contusion has enlarged significantly. Removing the lesion before it enlarges and causes neurological damage may be the safest approach for the patient.
Surgery is done by way of craniotomy. Please see Operative Procedures section for more information on this procedure. Generally the bone flap is replaced once the surgery is finished. Sometimes, part of the skull may be shattered or heavily contaminated; in which case, the contaminated or shattered fragments may be removed and not replaced. In other cases, if the brain is very swollen, some neurosurgeons may decide not to replace the bone until the swelling decreases, which may take up to several weeks. The neurosurgeon may elect to place an ICP monitor or other types of monitors if these were not already in place. The patient is then returned to the neurocritical care unit for observation and additional care.
Disabilities resulting from a TBI depend upon the severity of the injury, the location of the injury, and the age and general health of the individual. Some common disabilities include problems with cognition (thinking, memory, and reasoning), sensory processing (sight, hearing, touch, taste, and smell), communication (expression and understanding), and behavior or mental health (depression, anxiety, personality changes, aggression, acting out, and social inappropriateness). More serious head injuries may result in stupor, an unresponsive state, but one in which an individual can be aroused briefly by a strong stimulus, such as sharp pain; coma, a state in which an individual is totally unconscious, unresponsive, unaware, and unarousable; vegetative state, in which an individual is unconscious and unaware of his or her surroundings, but continues to have a sleep-wake cycle and periods of alertness; and a persistent vegetative state (PVS), in which an individual stays in a vegetative state for more than a month.
Recovery Process and Effects of TBI
Since our brain defines who we are, the consequences of a brain injury can affect all aspects of our lives, including our personality. Brain injuries do not heal like other injuries. Recovery is a functional recovery, based on mechanisms that remain uncertain. No two brain injuries are alike and the consequence of two similar injuries may be very different. Symptoms may appear right away or may not be present for days or weeks after the injury.
One of the consequences of brain injury is that the person often does not realize that a brain injury has occurred. TBI can cause a host of physical, cognitive, social, emotional, and behavioral effects, and outcome can range from complete recovery to permanent disability or death. CT and MRI have led physicians to improved diagnosis and treatment, and therefore, improved outcome. Depending on the injury, treatment required may be minimal or may include interventions such as medications and emergency surgery. Moderately to severely injured patients receive rehabilitation that involves individually tailored treatment programs in the areas of physical therapy, occupational therapy, speech/language therapy, physiatry (physical medicine), psychology/psychiatry, and social support.