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Overview of Head Injuries


Gordon Mao

, MD, Indiana University School of Medicine

Reviewed/Revised Mar 2023
Topic Resources

Head injuries that involve the brain are particularly concerning.

  • Common causes of head injuries include falls, motor vehicle crashes, assaults, and mishaps during sports and recreational activities.

  • People with minor head injuries may have a headache or dizziness.

  • People with more severe head injuries may lose consciousness or have symptoms of brain dysfunction.

  • Computed tomography is used to check for severe head injuries.

  • Treatment of people with severe head injuries aims to ensure that the brain gets sufficient oxygen and that pressure in the brain remains normal.

The thick, hard bones of the skull help protect the brain from injury. Also, the brain is surrounded by layers of tissue (meninges) containing cerebrospinal fluid, which cushions the brain. Consequently, most bumps and knocks on the head do not injure the brain. Head injuries that do not affect the brain are considered minor.

Head injuries may cause brain injury (traumatic brain injury or TBI).

In the United States, about 50 in 10,000 people have a head injury each year. In 2019, TBIs contributed to

  • About 223,000 people being hospitalized

  • About 60,000 deaths

TBIs contribute to about 30% of all deaths caused by injuries of any kind. About 25 to 33% of people in the United States who have a severe head injury die. About 5.3 million people have permanent disabilities due to head injury.

Head injuries include the following:

The brain may not be damaged even when external injuries are severe.

Causes of Head Injuries

Common causes of head injuries are falls (especially in older adults and young children), motor vehicle crashes, assaults, and mishaps during sports or recreational activities. Mishaps in the workplace (for example, while operating machinery) and firearms also cause head injuries. In 2014, the most common cause of TBIs was falls.

Often, injury is caused by direct impact. However, the brain can be damaged even if the head has not been hit. For example, violent shaking or sudden deceleration can damage the soft brain as it collides with the rigid skull. In such cases, there may be no visible injuries to the head.

Symptoms of Head Injuries

Minor head injury

A bump may appear on the head. If the scalp is cut, bleeding may be profuse because the scalp has many blood vessels close to the skin surface. Consequently, a scalp injury may appear to be more serious than it is.

Did You Know...

  • Because the scalp has many blood vessels, a scalp injury may bleed profusely even if the injury itself is not serious.

Common symptoms of minor head injuries may include headache and the sensation of spinning or light-headedness. Some people also have mild confusion, nausea, and, more commonly in children, vomiting. Young children may simply become irritable.

A concussion Concussion A concussion is an alteration in mental function or level of awareness caused by a head injury. A concussion may involve a loss of consciousness, can occur without obvious damage to brain structures... read more is a temporary, brief change in mental function without damage to the structure of the brain. Often, people lose consciousness briefly (usually a few minutes or less), but they may simply become confused or be unable to recall events and experiences (amnesia) that occurred shortly before or soon after the injury.

For some time after a concussion, people may experience headache, dizziness, fatigue, poor memory, inability to concentrate, trouble sleeping, difficulty thinking, irritability, depression, and anxiety. These symptoms are called the postconcussion syndrome.

Severe head injury

People may have some of the same symptoms as occur with minor head injury. Some symptoms, such as headache, may be more severe.

Also, symptoms often start with a period of unconsciousness that begins at the time of impact. How long people remain unconscious varies. Some people awaken in seconds, while others do not awaken for hours or even days. On awakening, people often are drowsy, confused, restless, or agitated. They may also vomit, have seizures, or both. Balance and coordination may be impaired. Depending on which area of the brain is damaged, the ability to think, control emotions, move, feel, speak, see, hear, and remember may be impaired—sometimes permanently.

Herniation: The Brain Under Pressure

Bleeding or swelling in the brain can cause pressure that forces the brain downward in the skull. The result may be a herniation, in which brain tissue is forced through a small natural opening in the relatively rigid sheets of tissue that separate the brain into right and left compartments and into upper and lower compartments. (These dividers are extensions of the outer layer of tissue covering the brain, the dura mater.) Herniation compresses brain tissue and thus damages it.

The most common type of herniation is a transtentorial herniation. Part of the temporal lobe is forced through the tentorial notch—the opening in the sheet of tissue between the temporal lobe and cerebellum. The pupil of the eye may become dilated and may not constrict in response to light. A transtentorial herniation can have catastrophic consequences, including paralysis, stupor, coma, abnormal heart rhythms, disturbances or cessation of breathing, cardiac arrest, and death.

Herniation: The Brain Under Pressure

An injured brain may bleed or swell because fluid accumulates (called cerebral edema). This bleeding and swelling gradually increase the pressure inside the skull, called intracranial pressure. Even mild bleeding and swelling can increase intracranial pressure a lot because the skull cannot expand to accommodate any increase in its contents. As the intracranial pressure increases, it limits the amount of blood that can flow through the brain. The limited blood flow prevents the brain from working normally and causes symptoms. The first symptoms of increased intracranial pressure include worsening headache, impaired thinking, a decreased level of consciousness, and vomiting. Later, the person may become unresponsive. The pupils may widen (dilate).

Eventually (usually within a day or two of injury), the increased pressure may force the brain downward, causing a herniation of the brain—an abnormal protrusion of brain tissue through a natural opening between the compartments of the brain. Herniation of the brain can cause coma or even death if too much pressure is put on the brain stem, the lower part of the brain, which controls such vital functions as heart rate and breathing. Even without herniation, if intracranial pressure gets high enough, it can shut off blood flow through the brain, leading rapidly to brain death Brain Death Brain death is the permanent loss of brain activity. As a result, people cannot breathe or maintain other vital functions on their own, and they permanently lose all awareness and capacity for... read more .

Diagnosis of Head Injuries

  • A doctor's evaluation

  • Computed tomography or sometimes magnetic resonance imaging

Minor head injury

Diagnosis of minor head injuries is based on a person’s symptoms and results of the examination.

Injured people are checked for symptoms that indicate brain function could be worsening. These symptoms include the following:

  • Repeated vomiting

  • Severe headache

  • Inability to feel or move an arm or leg

  • Inability to recognize people or the surroundings

  • Loss of balance

  • Problems with speaking or seeing

  • Lack of coordination

  • Abnormal breathing

  • Seizures

These symptoms may develop hours or sometimes days after the original injury. If these symptoms occur, prompt medical attention is essential.

If a head injury causes loss of consciousness, even briefly, immediate evaluation by a doctor is necessary. If doctors observe symptoms or findings that indicate possible brain injury, computed tomography (CT) or sometimes magnetic resonance imaging (MRI) is done. CT is usually done first because it can be done rapidly and can detect accumulated blood (hematomas), bruises (contusions), skull fractures, and sometimes widespread nerve damage (diffuse axonal injury). MRI may be useful later to check for diffuse axonal injury, injury to the brain stem (which controls levels of consciousness and vital body functions), and less obvious brain injuries that may not have been visible on CT. MRI can also help doctors predict prognosis.

Skull x-rays are rarely helpful.

Recognizing a Serious Head Injury

Most head injuries are not serious. A serious head injury can be recognized based on certain symptoms. Many of these symptoms indicate that brain functioning is worsening. If any of them occur, medical attention should be sought immediately.

  • Vomiting, irritability, or drowsiness that continues for more than 6 hours

  • Loss of consciousness

  • Inability to move or feel part of the body

  • Inability to recognize people or the surroundings

  • Inability to maintain balance

  • Problems with speaking or seeing (for example, slurred speech, blurred vision, or blind spots)

  • Drainage of clear fluid (cerebrospinal fluid) from the nose or ear

  • Severe headache

Severe head injury

Diagnosis and treatment of severe head injuries are done at the same time.

If the injury may affect other parts of the body (for example, after a motor vehicle crash) or the person is unconscious, an ambulance or 911 (in the United States) should be called.

When the person who may have a severe head injury reaches the hospital, doctors and nurses do a physical examination to determine whether the injury is serious. First, they check vital signs, including heart rate, blood pressure, and breathing. A person who is not breathing adequately may need a ventilator.

Doctors then quickly check the following:

  • Whether the person is oriented and able to respond to commands

  • Whether or how much stimulation (such as speaking, shouting, or squeezing a finger) is needed to make the person open their eyes

  • Whether the person has basic brain function by checking the size of the pupils and their reaction to light, the ability to move the arms and legs, the use of language, coordination, and reflexes

When doctors are sure that the person is not in immediate danger, a complete neurologic examination Neurologic Examination When a neurologic disorder is suspected, doctors usually evaluate all of the body systems during the physical examination, but they focus on the different parts of the nervous system. Examination... read more is done. This examination may help doctors determine the severity and location of the injury.

Doctors periodically check the person to determine whether the person is improving or getting worse.

CT is done to check for possible brain damage. Sometimes MRI is done in addition to CT. X-rays of the skull are usually unnecessary. They can identify skull fractures but reveal very little about brain damage. X-rays or CT of the neck is done when necessary to determine whether the neck is broken (because a strong blow to the head can also injure the neck).

Did You Know...

  • The degree of external head injury may have little to do with the degree of brain injury.

Treatment of Head Injuries

  • For minor head injuries, treatment of symptoms

  • For severe head injuries, treatment to maintain vital functions and to limit complications

Minor head injury

If a head injury is minor and causes no symptoms other than pain at the site of injury, mild analgesics such as acetaminophen may be used. Aspirin or any other nonsteroidal anti-inflammatory drug should not be taken because these medications may worsen any bleeding in the brain or skull. Doctors use stitches (sutures) or medical staples to close cuts and then apply gauze or bandages.

If people did not lose consciousness or lost it only briefly and if their examination results are normal, they may be discharged home as long as a family member or friend can check them for certain symptoms every few hours during the first 24 hours after the injury. The family member or friend should bring them to the hospital if any of the following potentially serious symptoms develop:

  • Reduced alertness and awareness of the surroundings

  • Problems with vision, hearing, or walking

  • Numbness or paralysis of a body part

  • A headache that is getting worse

  • Vomiting

  • Deterioration of mental function (such as becoming confused, not being able to recognize people, or behaving abnormally)

  • Seizures

If people have lost consciousness for longer than a few moments or have abnormal examination results, they are usually kept in the emergency department or hospital for observation.

Children who have had a minor head injury may be allowed to sleep, but they should be awakened every few hours and checked for symptoms.

Did You Know...

  • Acetaminophen is the best analgesic to take after a minor head injury.

Severe head injury

If the injury may affect other parts of the body (for example, after a motor vehicle crash) or if the person is unconscious, an ambulance should be called. When emergency personnel are moving a person who has had a severe head injury, they take great care to avoid making the injuries worse. The neck should be assumed to be broken until proved otherwise. In such cases, the person’s head, neck, and spine are stabilized. Usually, the person is put in a hard neck collar, strapped to a firm board, and carefully padded to prevent movement.

People with severe head injuries are admitted to the hospital, usually to an intensive care or critical care unit.

The first priority is to keep blood pressure and levels of oxygen and carbon dioxide in the blood at desirable levels. If the head injury is severe, the areas of the brain that control breathing may be affected. Also, the reflex that protects the windpipe (trachea) may not be functioning. (This reflex prevents saliva and other substances in the mouth from being inhaled.) For these reasons, a breathing tube is usually inserted through the mouth into the windpipe to help people breathe while doctors treat other problems, such as swelling in the brain. If the head injury is very severe, mechanical ventilation Mechanical Ventilation Mechanical ventilation is use of a machine to aid the movement of air into and out of the lungs. Some people with respiratory failure need a mechanical ventilator (a machine that helps air get... read more may be used.

Doctors control blood pressure and minimize the amount of brain swelling by adjusting the amount of intravenous fluids given and sometimes by giving intravenous drugs that increase fluid excretion (diuretics, such as mannitol and furosemide) or a concentrated salt solution (hypertonic saline). The concentrated salt solution may help minimize brain swelling more effectively than diuretics. Managing oxygen and carbon dioxide levels in the blood can help relieve pressure within the skull caused by swelling and ensure that the brain is getting enough oxygen. Doctors can control these levels by adjusting the amount of oxygen given and the rate and depth of breaths given by the ventilator. The head of the bed may be raised to prevent excessive pressure within the skull and brain.

A small pressure gauge may be implanted inside the skull to measure pressure within the skull and to determine how well the treatments are preventing or treating pressure elevation within the brain. Alternatively, a catheter may be inserted into one of the spaces (ventricles) within the brain. The ventricles contain cerebrospinal fluid, which flows over the surface of the brain between the layers of tissue that cover the brain (meninges). The catheter can be used to monitor the pressure and to drain cerebrospinal fluid, reducing the pressure within the skull. Sometimes doctors need to surgically remove a large piece of the skull to relieve the pressure; the piece of skull is replaced after the swelling goes down.

Did You Know...

  • In a person with a severe head injury, the neck should not be moved because it may be broken.

Pain is treated. Opioid pain relievers may be needed. People may need to be sedated because too much muscle activity can be harmful. Fever is treated. If seizures occur, anticonvulsants are given.

Doctors closely monitor the function of other organs, such as the kidneys, heart, lungs, and intestine because severe head injury can impair function of those organs.

Prognosis for Head Injuries

Minor head injury

Most people who have had a minor head injury recover completely, particularly if symptoms of postconcussion syndrome do not develop.

Symptoms of postconcussion syndrome are common during the week after brain injury. They often resolve during the second week. However, sometimes symptoms persist for months or, rarely, years. People who have had a concussion seem to be more susceptible to another one, particularly if the new injury occurs before symptoms from the previous concussion have completely gone away (as may happen in sports-related concussions Sports-Related Concussion A concussion is a temporary change in brain function after a head injury without any signs of brain damage on imaging tests, such as computed tomography (CT) or magnetic resonance imaging (MRI)... read more , often when an athlete resumes playing too quickly).

Severe head injury

For adults who have had a severe head injury, most recovery occurs within the first 6 months, although some improvement may continue for up to several years. Children tend to recover more fully, regardless of the injury’s severity, and they continue to improve for a much longer time.

The eventual consequences of a severe head injury range from complete recovery to permanent problems or disabilities of varying degrees to death.

Common long-term problems include the following:

  • Amnesia (loss of memory for previous events and trouble forming new memories)

  • Behavioral problems (such as anxiety, restlessness, impulsivity, lack of inhibition, or lack of motivation)

  • Sudden mood swings

  • Depression

  • Sleep disturbances

  • Loss of smell

  • Decreased intellectual function

Recovery of memory after loss of consciousness due to a severe head injury depends on how quickly consciousness is regained. People who regain consciousness in the first week are most likely to recover their memory.

Rarely, a seizure disorder develops after a severe head injury. It usually starts soon after the injury but may develop up to 4 years later.

The type and severity of disabilities depend on where and how badly the brain was damaged. Different areas of the brain Brain Dysfunction by Location Because different areas of the brain control specific functions, the location of brain damage determines the type of dysfunction that results. Which side of the brain is affected is also important... read more control specific functions. Some functions, such as vision and control of arm and leg movements, are controlled by unique areas on one side of the brain. Damage to any of these areas usually causes impairment of the corresponding function and thus permanent disability.

Undamaged areas of the brain sometimes take over functions that were lost when another area was damaged, resulting in partial recovery. However, as people age, the brain becomes less able to shift functions from one area to another. For example, language skills are handled by several parts of the brain in young children but are concentrated on one side of the brain (the left hemisphere) in adults. If the left hemisphere’s language areas are severely damaged before age 8, the right hemisphere can assume near-normal language function. However, damage to language areas during adulthood results in permanent disability.

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