Traumatic Brain Injury

There are several types of traumatic brain injuries (TBI), and they affect the lives of people of all ages. Anyone can experience a TBI, but data suggest that some groups are at greater risk of dying from a TBI or experiencing long-term health problems after the injury.

Diffuse axonal injury (DAI), one of the most common types of brain injury, refers to widespread damage to the brain's white matter. White matter is composed of bundles of axons (the projections of nerve cells that carry electrical impulses and connect various areas of the brain to one another). DAI usually results from rotational forces (twisting) or sudden forceful stopping that stretches or tears these axon bundles. This damage commonly occurs in auto accidents, falls or sports injuries. DAI can disrupt and break down communication among nerve cells (neurons) in the brain. It also leads to the release of brain chemicals that can cause further damage. Brain damage may be temporary or permanent and recovery can be prolonged.

Concussion is a type of mild TBI that may be considered a temporary injury to the brain but could take minutes to several months to heal. Concussion can be caused by a number of things, including a bump, blow or jolt to the head; sports injury or fall; motor vehicle accident; weapons blast; or a rapid acceleration or deceleration of the brain within the skull, such as the person having been violently shaken. The individual either suddenly loses consciousness or has a sudden altered state of consciousness or awareness. A second concussion closely following the first one causes further damage to the brain—the so-called second-hit phenomenon—and can lead to permanent damage or even death in some instances. Post-concussion syndrome involves symptoms that last for weeks or longer.

Hematomas are bleeding in and around the brain caused by a rupture to a blood vessel. Different types of hematomas form depending on where the blood collects relative to the meninges, the protective membranes surrounding the brain, which consist of three layers: dura mater (outermost), arachnoid mater (middle) and pia mater (innermost).

• Epidural hematomas involve bleeding into the area between the skull and the dura mater. These can occur within minutes to hours after damage to a brain vessel under the skull and are particularly dangerous.
• Subdural hematomas involve bleeding between the dura and the arachnoid mater, and, like epidural hematomas, exert pressure on the outside of the brain. They are very common in the elderly after a fall.
• Subarachnoid hemorrhage is bleeding between the arachnoid mater and the pia mater.
• Bleeding into the brain itself is called an intracerebral hematoma and damages the surrounding tissue.

Contusions are a bruising or swelling of the brain that occurs when very small blood vessels bleed into brain tissue. Contusions can occur directly under the impact site (a coup injury) or, more often, on the complete opposite side of the brain from the impact (a contrecoup injury). They can appear after a delay of hours to a day. Coup and contrecoup lesions generally occur when the head abruptly decelerates, which causes the brain to bounce back and forth within the skull (such as in a high-speed car crash or in shaken baby syndrome).

Skull fractures are breaks or cracks in one or more of the bones that form the skull. They are a result of blunt force trauma and can cause damage to the membranes, blood vessels and brain under the fracture. One main benefit of helmets is to prevent skull fractures.

Chronic traumatic encephalopathy (CTE) is a progressive neurological disorder associated with symptoms that may include problems with thinking, understanding and communicating; motor disorders (affecting movement); problems with impulse control and depression; confusion; and irritability. CTE occurs in those with extraordinary exposure to multiple blows to the head and as a delayed consequence after many years. Studies of retired boxers have shown that repeated blows to the head can cause issues including memory problems, tremors, lack of coordination, and dementia. Recent studies have demonstrated rare cases of CTE in other sports with repetitive mild head impacts (e.g., soccer, wrestling, football and rugby).

A single, severe TBI also may lead to a disorder called post-traumatic dementia (PTD), which may be progressive and share some features with CTE. Studies assessing patterns among large populations of people with TBI indicate that moderate or severe TBI in early or mid-life may be associated with increased risk of dementia later in life.

Examples of secondary damage:

• Hemorrhagic progression of a contusion (HPC) is when an initial contusion from the primary injury continues to bleed in and around the brain and expand over time. This creates a new or larger lesion—an area of tissue that has been damaged through injury or disease. This increased exposure to blood, which is toxic to brain cells, leads to swelling and further brain cell loss.
• A breakdown in the blood-brain barrier refers to the disruption of the network of cells that controls the movement of cells and molecules between the blood and fluid that surrounds the brain's nerve cells. Once the blood-brain barrier is disrupted, blood, plasma proteins and other foreign substances leak into the space between neurons in the brain and trigger a chain reaction that causes brain swelling. It also causes multiple biological systems to go into overdrive, including inflammatory responses, which can be harmful to the body if they continue for an extended period of time. It also permits the release of neurotransmitters, or chemicals used by brain cells to communicate, which can damage or kill nerve cells when depleted or overexpressed.
• Increased intracranial pressure is usually caused by brain swelling inside the confined area of the skull as a result of the injury. This pressure can damage brain tissue and can prevent blood flow to the brain and deprive it of the oxygen it needs to function.
• Other secondary damage can be caused by infections to the brain, low blood pressure or oxygen flow as a result of the injury, hydrocephalus (a buildup of fluid in the brain that can increase pressure on brain tissue) and seizures.

Shaken baby syndrome is a type of brain injury that happens when a baby or young child is shaken violently. When this happens, the brain can bounce back and forth against the skull which can cause bleeding, bruising and swelling.

A traumatic brain injury (TBI) can be caused by a forceful bump, blow or jolt to the head or body, or from an object that pierces the skull and enters the brain. Not all blows or jolts to the head result in a TBI. Some TBIs are considered primary, meaning the damage is immediate. Other outcomes of TBI can be secondary, meaning they can occur gradually over the course of hours or days, or appear weeks later. These secondary brain injuries are the result of reactive processes that occur after the initial head trauma.

The two broad types of head injuries are penetrating and non-penetrating.

• Penetrating TBI (also known as open TBI) happens when an object pierces the skull (e.g., a bullet, shrapnel, bone fragment or a weapon such as hammer or knife) and enters the brain tissue. Penetrating TBI typically damages only part of the brain.
• Non-penetrating TBI (also known as closed head injury or blunt TBI) is caused by an external force strong enough to move the brain within the skull. Causes include falls, motor vehicle crashes, sports injuries, blast injury or being struck by an object.

Some accidents such as explosions, natural disasters or other extreme events can cause both penetrating and non-penetrating TBI in the same person.

The leading causes of TBI include:

• Falls—According to data from the Centers for Disease Control and Prevention (CDC), falls are the most common cause of TBIs and occur most frequently among the youngest and oldest age groups.
• Blunt trauma accidents—Accidents that involve being struck by or against an object, particularly sports-related injuries, are a major cause of TBI.
• Vehicle-related injuries—Pedestrian-involved accidents, as well as accidents involving motor vehicles and bicycles, are the third most common cause of TBI.
• Assaults/violent assaults—Abuse-related TBIs are head injuries that result from domestic violence, shaken baby syndrome or gunshot wounds to the head. TBI-related deaths in children aged four and younger are most likely the result of assault.
• Explosions/blasts—TBIs caused by blast trauma from roadside bombs are a common injury to service members in military conflicts. The majority of these TBIs are classified as mild head injuries.

Adults aged 65 and older are at greatest risk for being hospitalized and dying from a traumatic brain injury, most likely from a fall. In every age group, serious TBI rates are higher for men than for women. Men are more likely to be hospitalized and are nearly three times more likely to die from a TBI than women.

Factors that can influence recovery from a TBI include genes and age.

Genes—Genetics may play a role in how quickly and completely a person recovers from a TBI. For example, researchers have found that apolipoprotein E ε4 (ApoE4)—a genetic variant associated with higher risk for Alzheimer's disease—is associated with worse health outcomes following a TBI. Much work remains to be done to understand how genetic factors, as well as how specific types of head injuries, affect recovery. This research may lead to new treatment strategies and improved outcomes for people with TBI.

Age—Studies suggest that age and the number of head injuries a person has suffered over their lifetime are two critical factors that impact recovery. For example, TBI-related brain swelling in children can be very different from the same condition in adults, even when the primary injuries are similar. Brain swelling in newborns, young infants and teenagers often occurs much more quickly than it does in older individuals. Evidence from very limited CTE studies suggest that younger people (ages 20 to 40) tend to have behavioral and mood changes associated with CTE, while those who are older (ages 50+) have more cognitive difficulties.

Compared with younger adults with the same TBI severity, older adults are likely to have less complete recovery. Older people also have more medical issues and are often taking multiple medications that may complicate treatment (e.g., blood-thinning agents when there is a risk of bleeding into the head). Further research is needed to determine if and how treatment strategies may need to be adjusted based on a person's age.

While anyone is at risk for getting a TBI, some groups have a greater likelihood of dying from a TBI or living with long-term problems that resulted from the injury.

People aged 75 years and older had the highest numbers and rates of TBI-related hospitalizations and deaths. This age groupaccounts for about 32 percent of TBI-related hospitalizations and 28 percent of TBI-related deaths.

American Indian/Alaska Native children and adults have higher rates of TBI-related hospitalizations and deaths than other racial or ethnic groups. Factors that contribute to this disparity include higher rates of motor vehicle crashes, substance use and suicide as well as difficulties in accessing appropriate healthcare.

In addition to differences in rates of TBI, racial and ethnic minority groups, particularly non-Hispanic Black and Hispanic patients, are less likely to receive follow-up care and rehabilitation following a TBI compared to non-Hispanic white patients. Racial and ethnic minorities are also more likely to have poor psychosocial, functional and employment-related outcomes after sustaining a TBI than non-Hispanic white individuals.

More than 450,000 U.S. service members were diagnosed with a TBI between 2000 and 2021. Military conflicts involve risks for TBI among service members; still, TBIs among this group most commonly occur when the person is not deployed, such as from a motor vehicle crash. Studies suggest that service members and veterans who have sustained a TBI may:

• Have ongoing symptoms
• Experience co-occurring health conditions, such as post-traumatic stress disorder (PTSD) and depression
• Have difficulty accessing healthcare (particularly mental health services)
• Report thinking about or planning a suicide attempt

Research in the United States and from other countries suggests almost half (46 percent) of people in correctional or detention facilities such as prisons and jails have a history of TBI, but the exact number is not known. Research shows an association between people in correctional or detention facilities with a history of TBI and:

• mental health problems, such as severe depression and anxiety
• substance use disorders
• difficulty controlling anger 
• suicidal thoughts and/or attempts

People in correctional or detention facilities with TBI-related problems may not be screened for a TBI or may face challenges with getting TBI-related care. These challenges may continue after a person is released from the facility.

Compared to the general population, people who experience homelessness are:

• Two to four times more likely to have a history of any type of TBI
• Up to 10 times more likely to have a history of a moderate or severe TBI

People who experience homelessness and have a history of TBI have worse overall physical and mental health and are more likely to report experiencing violence and/or trauma during childhood, substance use, and thinking about or attempting suicide.

Survivors of intimate partner violence who have a TBI due to an assault are more likely to:

• Be diagnosed with PTSD, insomnia and depression
• Report worse overall health

Low-income individuals and those without health insurance have less access to TBI care. Survivors of a moderate or severe TBI may face a difficult road to recovery that requires services such as physical therapy and mental health treatment for months or years in order to return to pre-injury function. TBI survivors with lower incomes or who are uninsured face significant barriers in accessing appropriate TBI care. Compared with patients who have private health insurance, those who are uninsured are:

• Less likely to receive a TBI procedure (e.g., craniectomy/craniotomy, ventriculostomy, intracranial pressure monitor placement, arterial line placement or central line placement)
• Less likely to receive inpatient services, such as rehabilitation
• More likely to die in the hospital

People living in rural areas have a greater risk of dying from a TBI compared to people living in urban areas. Some reasons for this disparity include:

• More time needed to travel to emergency medical care.
• Less access to a Level I trauma center (the highest level of medical care).
• Difficulty getting services, such as specialized TBI care.
• Children living in rural areas are more likely to get a TBI and to die as a result of this injury compared to children living in urban areas. Children in rural areas may also be more likely to experience delays in getting TBI-related care and be unnecessarily transferred to another hospital for treatment.

The best treatment for traumatic brain injuries is prevention. Unlike most neurological disorders, head injuries can be prevented. According to the CDC, the following actions can help prevent TBIs:

• Wear a seatbelt when you drive or ride in a motor vehicle  
• Wear the correct helmet and make sure it fits properly when riding a bicycle, skateboarding and playing sports like hockey and football
• Install window guards and stair safety gates at home for young children
• Never drive under the influence of drugs or alcohol
• Improve lighting and remove rugs, clutter and other trip hazards in the hallway
• Use non-slip mats and install grab bars next to the toilet and in the tub or shower for older adults
• Install handrails on stairways
• Improve balance and strength with a regular physical activity program
• Ensure children's playgrounds are made of shock-absorbing material, such as hardwood mulch or sand

Some types of traumatic brain injuries can cause temporary or short-term problems with normal brain function, including problems with how the person thinks, understands, moves, communicates and acts. More serious TBI can lead to severe and permanent disability, and even death. Seek immediate medical attention if you experience any of the following physical, cognitive/behavioral or sensory symptoms, especially within the first 24 hours after a TBI:

Physical Symptoms:

• Headache
• Convulsions or seizures
• Blurred or double vision
• Unequal eye pupil size or dilation
• Clear fluids draining from the nose or ears
• Nausea and vomiting
• New neurologic deficit, such as slurred speech; weakness of arms, legs or face; loss of balance

Cognitive/Behavioral Symptoms:

• Loss of or change in consciousness anywhere from a few seconds to a few hours
• Decreased level of consciousness (e.g., hard to awaken)
• Mild to profound confusion or disorientation
• Problems remembering, concentrating or making decisions
• Changes in sleep patterns (e.g., sleeping more, difficulty falling or staying asleep); inability to awaken from sleep
• Frustration, irritability

Perception/Sensation Symptoms:

• Light-headedness, dizziness, vertigo, or loss of balance or coordination
• Blurred vision
• Hearing problems, such as ringing in the ears
• Bad taste in the mouth
• Sensitivity to light or sound
• Mood changes or swings, agitation, combativeness or other unusual behavior
• Feeling anxious or depressed
• Fatigue or drowsiness; a lack of energy or motivation

Other Symptoms
Headache, dizziness, confusion and fatigue tend to start immediately after an injury but resolve over time. Emotional symptoms such as frustration and irritability tend to develop during recovery.

TBI in Children
Children might be unable to let others know that they feel different following a blow to the head. A child with a TBI may display the following signs or symptoms:

• Changes in eating or nursing habits
• Persistent crying, irritability or crankiness; inability to be consoled
• Changes in ability to pay attention
• Lack of interest in a favorite toy or activity
• Changes in sleep patterns
• Seizures
• Sadness or depression
• Loss of a skill, such as toilet training
• Loss of balance or unsteady walking
• Vomiting

Shaken baby syndrome is known to cause long-term brain damage or even death. Symptoms of shaken baby syndrome may include:

• Bleeding, bruising or swelling in the brain
• Bleeding in the retina (a part of the eye)
• Unconsciousness
• Seizures
• Breathing difficulties
• Extreme irritability
• Vomiting
• Pale or blue-colored skin

Some symptoms may be noticed immediately, while others become evident as the child grows older. Babies and young children who have been shaken violently may develop serious health problems, including:

• Permanent brain damage
• Vision problems and possibly loss of sight
• Problems with body movement and movement control
• Weakness
• Seizures
• Abnormal physical sensations or perceptions
• Neck and spinal cord damage
• Intellectual disability

Traumatic brain injury (TBI)–related damage can be confined to one area of the brain, known as a focal injury, or it can occur over a more widespread area, known as a diffuse injury. The type of injury also affects how the brain is damaged.

All TBIs require immediate assessment by a professional who has experience evaluating head injuries. A neurological exam will judge motor and sensory skills and test hearing and speech, coordination and balance, mental status, and changes in mood or behavior, among other abilities. Screening tools for coaches and athletic trainers can identify the most concerning concussions for medical evaluation.

Initial assessments may rely on standardized instruments such as the Acute Concussion Evaluation (ACE) form from the Centers for Disease Control and Prevention (CDC) or the Sport Concussion Assessment Tool 2, which provide a systematic way to assess a person who has suffered a mild TBI. Reviewers collect information about the characteristics of the injury, the presence of amnesia (loss of memory) and/or seizures, as well as the presence of physical, cognitive, emotional and sleep-related symptoms. The ACE is also used to track symptom recovery over time. It also takes into account risk factors (including concussion, headache and psychiatric history) that can affect how long it takes to recover from a TBI.

Diagnostic imaging. When necessary, medical providers will use brain scans to evaluate the extent of the primary brain injuries and determine if surgery will be needed to help repair any damage to the brain. The need for imaging is based on a physical examination by a doctor and a person's symptoms.

• Computed tomography (CT) is the most commonly used imaging technology to assess people with suspected moderate to severe TBI. CT creates a two-dimensional image of organs, bones and tissues and can show a skull fracture or any brain bruising, bleeding or swelling.
• Magnetic resonance imaging (MRI) produces detailed images of body tissue. It may be used after the initial assessment and treatment as it is a more sensitive test and picks up subtle changes in the brain that the CT scan might have missed. Significant advances have been made in the past decade to image milder TBI damage. For example, diffusion tensor imaging can image white matter tracts, more sensitive tests like fluid-attenuated inversion recovery can detect small areas of damage, and susceptibility-weighted imaging very sensitively identifies bleeding. Despite these improvements, currently available imaging technologies, blood tests and other measures remain inadequate for detecting these changes in a way that can help diagnose mild concussive injuries.

Neuropsychological tests to gauge brain functioning are often used along with imaging in people who have suffered mild TBI. Such tests involve performing specific cognitive tasks that help assess memory, concentration, information processing, executive functioning, reaction time and problem solving.

The Glasgow Coma Scale is the most widely used tool for assessing the level of consciousness after TBI. The standardized 15-point test measures a person's ability to open their eyes and respond to spoken questions or physical prompts for movement.

Many athletic organizations recommend establishing a baseline picture of an athlete's brain function at the beginning of each season, ideally before any head injuries occur. Baseline testing should begin as soon as a child begins a competitive sport. Brain function tests yield information about an individual's memory, attention and ability to concentrate and solve problems. Brain function tests can be repeated at regular intervals (every one to two years) and also after a suspected concussion. The results may help healthcare providers identify any effects from an injury and allow them to make more informed decisions about whether a person is ready to return to their normal activities.

For shaken baby syndrome, doctors can use imaging tests like magnetic resonance imaging (MRI) or computed tomography (CT) to diagnose the disorder. Treatment must be given quickly, and some children may need surgery to stop bleeding in the body or machines to help them breathe.

When it comes to treating traumatic brain injury (TBI), many factors—including the size, severity and location of the brain injury—influence treatment and how quickly a person might recover. One of the critical elements to a person's prognosis is the severity of the injury. Although brain injury often occurs at the moment of head impact, much of the damage related to severe TBI develops from secondary injuries that happen days or weeks after the initial trauma. For this reason, people who receive immediate medical attention at a certified trauma center tend to have the best health outcomes.

Some people with mild TBI such as concussion may not require treatment other than rest and over-the-counter pain relievers. Treatment should focus on symptom relief and “brain rest.” Monitoring by a healthcare practitioner is important to note any worsening of symptoms or new ones.

Children and teens who have a sports-related concussion should stop playing immediately and return to play only after being approved by a concussion injury specialist.

Preventing future concussions is critical. While most people recover fully from a first concussion within a few weeks, the rate of recovery from a second or third concussion is generally slower.

Even after symptoms resolve entirely, people should return to their daily activities gradually once they are given permission by a doctor. There is no clear timeline for a safe return to normal activities, although there are guidelines such as those from the American Academy of Neurology and the American Medical Society for Sports Medicine to help determine when athletes can return to practice or competition. Further research is needed to better understand the effects of mild TBI on the brain and to determine when it is safe to resume normal activities.

Those with severe TBI should seek immediate treatment that focuses on preventing death; stabilizing the person's spinal cord, heart, lung and other vital organ functions; ensuring proper oxygen delivery and breathing; controlling blood pressure; and preventing further brain damage. Emergency care staff will monitor the flow of blood to the brain, brain temperature, pressure inside the skull and the brain's oxygen supply.

Surgery may be needed to for emergency medical care and to treat secondary damage, including:

• Relieving pressure inside the skull (inserting a special catheter through a hole drilled into the skull to drain fluids)
• Removing debris or dead brain tissue (especially for penetrating TBI)
• Removing hematomas
• Repairing skull fractures

In-hospital strategies for managing people with severe TBI aim to prevent conditions including:

• Infection, particularly pneumonia
• Deep vein thrombosis (blood clots that occur deep within a vein; risk increases during long periods of inactivity)

People with TBI may need nutritional supplements to minimize the effects that vitamin, mineral and other dietary deficiencies may cause over time. Some individuals may even require tube feeding to maintain the proper balance of nutrients.

After the acute care period of in-hospital treatment, people with severe traumatic brain injuries are often transferred to a rehabilitation center, where a multidisciplinary team of healthcare providers helps with recovery.

The rehabilitation team includes neurologists, nurses, psychologists, nutritionists, as well as physical, occupational, vocational, speech and respiratory therapists.

Therapy is aimed at improving the person's ability to handle activities of daily living and to address cognitive, physical, occupational and emotional difficulties. Treatment may be needed on a short-term basis or throughout a person's life. Some therapy is provided through outpatient services.

Cognitive rehabilitation therapy (CRT) is a strategy aimed at helping individuals regain their normal brain function through an individualized training program. Using this strategy, people may also learn compensatory strategies for coping with persistent deficiencies involving memory, problem solving and the thinking skills to get things done. CRT programs tend to be highly individualized and their success varies. A 2011 Institute of Medicine report concluded that cognitive rehabilitation interventions need to be developed and assessed more thoroughly.

Babies who survive shaken baby syndrome are typically diagnosed with developmental delays, behavior issues, blindness and learning delays as well as long-term brain damage.

To further your understanding of your diagnosis and to contribute to cutting-edge research, consider participating in a clinical trial so clinicians and scientists can learn more about causes, symptoms, treatment and prevention. Clinical research uses human volunteers to help researchers learn more about a disorder and perhaps find better ways to safely detect, treat or prevent disease.

All types of volunteers are needed—those who are healthy or may have an illness or disease—of all different ages, sexes, races and ethnicities to ensure that study results apply to as many people as possible, and that treatments will be safe and effective for everyone who will use them.

For information about participating in clinical research, visit NIH Clinical Research Trials and You. Learn about clinical trials currently looking for participants at Clinicaltrials.gov.