Brain Injuries

Brain injuries usually result from impact or trauma to the brain that can lead to a variety of medical problems, depending on the nature of the injury.

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* access to the brain, leading to dangerous infections. The most common type of brain injury results from minor trauma. Such injuries usually do not involve loss of consciousness (being “knocked out”). More serious brain injuries may occur with or without a skull fracture as a result of impact trauma.

The brain is surrounded by a liquid called cerebrospinal (seh-ree-bro-SPY-nal) fluid (CSF). CSF acts as a cushion to absorb some of the force of impact. Unfortunately, in the course of an impact injury to the head, the brain can shift, and tissue damage can occur, especially from rapidly speeding up or slowing down—much like what happens to Jell-O in a container that is dropped or suddenly yanked. The brain damage may be at the point of impact, opposite the point of impact, or spread across any area of the brain. The delicate nerve tissues, the blood vessels, or the membranes surrounding the brain, called the meninges (meh-NIN-jeez), may be torn or injured. The damage may result in abnormal brain activity, cerebral hemorrhage * or cerebral edema * . Because the skull is rigid and there is only limited room inside it, the swelling brain causes increasing pressure inside the skull, which can force brain tissue to press directly against the inside of the skull, resulting in more damage.

Impact to the head may cause leakage of fluid and blood from blood vessels in the scalp, forming a painful lump. A stronger blow can tear the meninges, the protective membrane surrounding the brain, or injure the brain tissue itself.

Impact to the head may cause leakage of fluid and blood from blood vessels in the scalp, forming a painful lump. A stronger blow can tear the meninges, the protective membrane surrounding the brain, or injure the brain tissue itself. The bleeding and brain swelling this type of injury can produce may lead to increased pressure within the skull, resulting in a variety of problems including concussion and permanent brain damage.
Illustration by Frank Forney. © 2016 Cengage Learning®.

Illustration depicting three types of head injury: hairline fracture, depressed fracture, and subdural hematoma.

Illustration depicting three types of head injury: hairline fracture, depressed fracture, and subdural hematoma.
Illustration by Electronic Illustrators Group. © 2016 Cengage Learning®.

What Are the Causes of Brain Injury?

* , balance, ability to move, memory, or vision.

Not all brain injuries are the result of trauma. The brain can be damaged by lack of oxygen, as with drowning, near-drowning, or a particularly difficult birth. The brain can also be damaged through starvation, vitamin deficiencies, or certain other types of malnutrition. Toxins, such as heavy metals (e.g., lead), and the overuse or overdose of legal and/or illegal substances, such as alcohol and drugs, can irreversibly damage the brain. Additionally, a wide variety of medical illnesses can have an impact on the brain and central nervous system.

What Are the Signs and Symptoms of Brain Injury?

Brain injuries are difficult to diagnose because there may be many different signs or symptoms that are present immediately after injury or that may not show up for hours or days. Signs and symptoms may also vary from individual to individual and are dependent on the extent and location of the injury to the brain. In the event of any type of head injury, it is important to gather as much information as possible about the accident. Anyone who witnessed the accident may be able to provide details about exactly what happened and how the injured person acted after the accident.

Temporary amnesia (am-NEE-zha), or loss of memory, is common with many brain injuries. It is typical for the injured person not to remember what happened immediately before, during, and immediately after the accident. Brief periods of amnesia may occur during the recovery period after brain injuries. Longer-term amnesia is not common, except when a head injury is severe.

Brain injuries can affect a person cognitively (intellectually), physically, and emotionally. The following symptoms may be present at the time of the accident. While it is less common, some symptoms may appear hours, days, or even longer after the accident. Some of the following changes may be permanent depending on the extent and location of the brain injury:

What Are the Different Types of Brain Injury?

Minor Head Trauma

Anyone who suffers minor head trauma without loss of consciousness or other associated neurological * symptoms still should be watched closely. The injury may or may not be followed by symptoms such as vomiting, paleness of the skin, irritability, or sluggishness. If any of the symptoms last more than six hours or if they worsen, they may indicate a more severe injury. A doctor should be consulted immediately for a thorough evaluation.

Skull Fracture

A skull fracture, or injury to the bony structures protecting the brain, may or may not result in any neurological symptoms. In some cases the skull may have a noticeable depression (a “pushed in” appearance, like a dent), or there may be significant swelling or bleeding from the overlying scalp. Fractures may cause bruising or tearing of brain tissue or blood vessels on the meninges. The injured person may have seizures as a result of the injury. A skull fracture is a very serious injury and a doctor should examine the person as soon as possible after the injury if there is any possibility of skull fracture.


A concussion (con-CUH-shun) is a bruise-like injury to brain tissue caused by a direct blow or violent shaking. A concussion usually is associated with amnesia or a change in level of consciousness that lasts a few seconds to a few minutes after the trauma. The patient typically shows no other signs of neurological problems immediately after the trauma, but a condition known as postconcussion syndrome might follow a minor head injury. Patients with persistent postconcussion symptoms sometimes enter the hospital for observation. These symptoms include headache, dizziness, difficulty concentrating, varying degrees of amnesia, depression, apathy (a lack of interest or feeling), nausea, and anxiety. Repeated concussions, now termed repetitive head injury syndrome, are dangerous, can lead to significant neurological damage, and may increase the person's risk of sudden death.

Contusions and Lacerations

Contusions (con-TOO-zhuns) and lacerations (la-se-RAY-shuns), which are bruises and cuts to tissue, are serious problems when the brain is affected. Brain contusions and lacerations are often associated with serious head trauma that causes severe surface wounds and skull fractures. The symptoms a person shows depend on the part of the brain that is affected. Severe contusions and lacerations generally are associated with brain swelling. The initial trauma may also cause paralysis or even coma * for several days to weeks.

Hematomas * hematoma. This kind of hematoma begins forming immediately after injury and is common in severe head injuries. It causes growing pressure within the skull that eventually can lead to coma and even death if left untreated. Some subdural hematomas are formed by very slow blood vessel bleeding, so they may not produce symptoms for several days, or even weeks, after the injury. The symptoms may be overlooked because of the time lapse between the injury and the appearance of symptoms. Symptoms may include daily headaches that slowly increase in severity, impairments in aspects of thinking and memory, changing levels of consciousness, including increase in drowsiness and confusion, and gradual paralysis on one side of the body. Subdural hematomas can occur after a concussion.

Epidural * hematomas occur when blood leaking from damaged blood vessels is trapped between the membranes covering the brain and the skull. The symptoms of an epidural hematoma usually develop within hours of the injury. Symptoms may include worsening headache, various levels of consciousness, loss of motor skills * , and fixed gaze (of one or both eyes) with dilated (widened) pupils. Epidural hematomas are less common than subdural hematomas, but they require prompt medical attention because the bleeding can quickly compress the brain and cause permanent or fatal brain damage.

How Do Doctors Diagnose and Treat Brain Injuries?

The severity of brain injuries may be difficult to determine accurately. Doctors must evaluate all the symptoms, listen to descriptions of the accident from both the injured person and witnesses, and rely on a variety of tests and procedures to make a diagnosis. The problems of diagnosis are even more complicated when the patient is unconscious or is experiencing amnesia.

The diagnosis begins with a physical examination. The doctor checks the state of consciousness, breathing patterns, pupil size and the pupils' reaction to light, and movement of the eyes and limbs. The doctor may use x-rays to find fractures of the skull. In addition to x-rays, the doctor may use special imaging studies, such as computed tomography * (CT) scans or magnetic resonance imaging *

Sports-Related Brain Injury

Every year between 1.4 million and 1.7 million people in the United States are treated for a traumatic brain injury.

For both adults and children, cycling accidents are the greatest cause of injury, over any other sport or activity.

Players of almost any sport can be injured, but those who play football, soccer, or ice hockey and those who wrestle or box may be most in danger of severe brain injuries. In just one playing season, as many as 10 percent of college football players and 20 percent of high school football players may have serious head injuries. The U.S. Centers for Disease Control and Prevention estimates an incidence of approximately 300,000 concussions among high school and college football players every year. Sports participants who are hit in the head repeatedly, such as boxers, may have permanent disabilities as the result of many injuries to the brain.

The American Medical Association in 2015 recommended the prohibition of all forms of combat sports, including boxing, for people under the age of 18.

Muhammad Ali (1942–2016), three-time world heavyweight boxing champion and Olympic gold medalist, developed Parkinson's disease, which may have resulted from his years in the ring. A person with Parkinson's disease usually has muscle rigidity, tremors, and twitches that may make it difficult to walk or even to talk. In severe cases, Parkinson's disease also may affect a person's mental abilities.

Skull fractures themselves seldom require special treatment. In most cases, the fracture heals by itself over time. In severe or penetrating cases of skull fracture, surgery may be required to remove fragments of the skull that may have been pushed into the brain.

Surgery is one method of treatment for injuries such as hematomas. Attempts to stop the bleeding associated with epidural hematomas usually are done as an emergency procedure to prevent further brain damage from increased pressure in the skull caused by the bleeding. Epidural hematomas may require repeated operations to remove blood clots. Damage to brain tissue cannot be repaired by surgery or medicine. The harmful effects of brain injuries respond best to aggressive treatment by rehabilitation teams, typically made up of specially trained physicians, rehabilitation nurses, psychologists, speech-language pathologists, physical and occupational therapists, and other professionals. Patients must be monitored constantly and their condition must be reevaluated as their behavior and symptoms change.

What Are the Long-Term Effects of Brain Injury?

Recovery from a minor brain injury, such as a first concussion, usually takes a short time (three to six months), and the recovery is often complete. For more serious injuries, degrees of recovery vary. Factors that predict good recovery are the patient's age (younger is better), duration of coma (longer is worse), presence of bleeding in the brain, and the site and amount of trauma to the head and brain. Patients who survive severe brain injury often face a long recovery process (years) and are left with permanent cognitive and physical disabilities.

Rehabilitation programs help patients regain their cognitive and emotional faculties. During the rehabilitation process, patients commonly have lapses of memory; behavioral changes, such as mood swings; emotional problems, such as anxiety or depression; changes in sleep patterns; decline in intellectual ability; and seizures. Psychological counseling and brain injury support groups are available to help patients and families deal with the long-term rehabilitation process.

Patients who end up in a coma or a persistent vegetative state (PVS) usually have the most severe types of brain injury. In these types of injuries, the cognitive centers of the brain are badly damaged, while the brain stem that controls bodily functions may remain intact.

Chronic traumatic encephalopathy (CTE)

Chronic traumatic encephalopathy is a condition characterized by brain degeneration likely caused by repeated head traumas. Initial signs and symptoms of CTE usually do not occur until decades after a person has experienced head traumas (ages 40-50). Typical signs and symptoms include a decline of recent memory and executive function, mood and behavioral disturbances (especially depression, impulsivity, aggressiveness, anger, irritability, suicidal behavior and eventual progression to dementia). As of 2016, CTE had only been possible to diagnose conclusively after death (via autopsy) because it is indistinguishable from many other brain conditions.

How Can Brain Injury Be Prevented?

Most brain injuries are the result of accidents or falls. Wearing safety belts in cars and helmets when using wheeled vehicles, such as bicycles and skateboards, can help prevent many of these injuries. Observing safety practices is important. Wearing a safety belt in the front seat of a car prevents the wearer from hitting the dashboard, steering wheel, or windshield. Wearing seat belts in the front or backseat keeps the wearer from being thrown around inside the vehicle or thrown out of the vehicle. Wearing a helmet while riding a bicycle or motorcycle or using a skateboard, hoverboard, or skates, helps protect the rider from injuries during falls. Helmets should be tight fitting and padded and have a chin strap. It is also important to wear helmets while playing contact sports such as football. Even in sports such as baseball, helmets should be worn whenever there is a possibility that the ball could strike the head.

See also Anemia, Bleeding, and Clotting • Bruises • Concussion • Consciousness • Dementia • Intellectual Disability • Memory and Amnesia • Seizures • Speech Disorders: Overview • Sports Injuries: Overview • Stupor and Coma • Substance Abuse • Trauma


Books and Articles

Esty, Mary Lee, and C. M. Shifflett. Conquering Concussion. Sewickly, PA: Round Earth, 2014.

Goldsmith, Connie. Traumatic Brain Injury: From Concussion to Coma. Minneapolis, MN: 21st Century Books, 2014.


Centers for Disease Control and Prevention. “Traumatic Brain Injury & Concussion.” (accessed March 20, 2016).


American Association of Neurological Surgeons. 45550 Meadowbrook Dr., Rolling Meadows, IL 60008. Toll-free: 888-566-AANS (2267). Website: (accessed March 20, 2016).

Brain Injury Association of America. 1608 Spring Hill Rd., Suite 110, Vienna, VA 20036. Toll-free: 800-444-6443. Website: (accessed March 20, 2016).

Brain Injury Resource Center. PO Box 84151, Seattle, WA 981045451. Telephone: 206-621-8558. Website: (accessed March 20, 2016).

Centers for Disease Control and Prevention. 1600 Clifton Rd., Atlanta, GA 30329. Toll-free: 800-232-4636. Website: (accessed March 20, 2016).

* bacteria (bak-TEER-ee-uh) are single-celled microorganisms, which typically reproduce by cell division. Some, but not all, types of bacteria can cause disease in humans. Many types can live in the body without causing harm.

* hemorrhage (HEH-muh-rij) is uncontrolled or abnormal bleeding.

* edema (eh-DEE-muh) is swelling in the body's tissues caused by excess fluids.

* level of consciousness is the state of wakefulness or alertness of an individual

* seizures (SEE-zhurs) are sudden bursts of disorganized electrical activity that interrupt the normal functioning of the brain, often leading to uncontrolled movements in the body and sometimes a temporary change in consciousness.

* double vision is a vision problem in which a person sees two images of a single object.

* neurological (nur-a-LAH-je-kal) refers to the nervous system, which includes the brain, spinal cord, and the nerves that control the senses, movement, and organ functions throughout the body.

* coma (KO-ma) is an unconscious state, like a very deep sleep. A person in a coma cannot be awakened and cannot move, see, or speak.

* subdural (sub-DOO-ral) means under the dura, the covering of the brain

* epidural (ep-I-DOO-ral) means above or outside the dura, the covering of the brain.

* motor skills are muscular movements or actions.

* computed tomography (kom- PYOO-ted toe-MAH-gruh-fee), or CT, also called computerized axial tomography (CAT), is a technique in which a machine takes many x-rays of the body to create a three-dimensional picture.

* magnetic resonance imaging, or MRI, uses magnetic waves instead of x-rays to scan the body and produce detailed pictures of the body's structures.

Disclaimer:   This information is not a tool for self-diagnosis or a substitute for professional care.

(MLA 8th Edition)