Overview of Head Injuries
About half of head injuries result from motor vehicle crashes. Falls, assaults, and mishaps during sports and recreational activities are also common causes.
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 13 in 10,000 people sustain minor head injury, and about 3 in 10,000 sustain severe head injury each year. In the United States, from 2002 to 2006, about 1.7 million civilians had TBI each year. About 1.4 million were treated and released from emergency departments. About 275,000 were hospitalized and discharged alive, and 52,000 died. TBI is responsible for about 33% of all deaths caused by injuries of any kind. About 5.3 million people have permanent disabilities due to head injury. About 25 to 33% of people in the United States who have a severe head injury die.
About half of head injuries result from motor vehicle crashes, and head injuries occur in more than 70% of severe motor vehicle crashes. Other common causes are falls (especially in older adults and young children), assaults, and mishaps during sports or recreational activities. Mishaps in the workplace (for example, while operating machinery) and firearms also cause head injuries. 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.
Head injuries include injury to the scalp, skull fractures, concussions, bruises (contusions) and tears (lacerations) of the brain, accumulation of blood within the brain or between the brain and skull (intracranial hematoma), and damage to nerve cells throughout the brain (diffuse axonal injury). Bleeding can also develop between the layers that cover the brain (subarachnoid hemorrhage). Alternatively, the brain may not be damaged even when external injuries are severe.
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.
Common symptoms may include headache and the sensation of spinning or light-headedness. Some people also may have mild confusion, nausea, and, more commonly in children, vomiting. Young children may simply become irritable.
A concussion (see Concussion) 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.
People may have some of the same symptoms as occur with minor head injury. Some, 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.
Clear fluid or blood may drain from the nose, ears, or both if a person has a fracture of the base of the skull (see Skull Fracture).
Herniation: The Brain Under Pressure
An injured brain may bleed or swell. This bleeding and swelling gradually increase the pressure on the brain because the skull cannot expand to accommodate any increase in its contents. As the pressure increases, the person’s symptoms worsen and new symptoms appear. The first symptoms of increased pressure within the skull include worsening headache, impaired thinking, decreased level of consciousness, and vomiting. Later, the person may become unresponsive. A pupil may widen. 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.
Most people 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 an athlete who resumes playing too quickly—see Sports-Related Concussion).
For adults who have had a severe head injury, most recovery occurs within the first 6 months, although improvement may continue for up to 2 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 amnesia, behavioral problems (such as anxiety, restlessness, impulsivity, lack of inhibition, or lack of motivation), sudden mood swings, depression, sleep disturbances, loss of smell, and 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. A seizure disorder may develop up to 4 years after a severe head injury.
The type and severity of disabilities depend on where and how badly the brain was damaged. 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.
Rehabilitation can help people minimize the effect of most disabilities on function (see Rehabilitation After a Brain Injury).
Diagnosis of minor head injuries is based on a person’s symptoms and results of the examination. 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 drugs 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. Someone should check the injured person every few hours during the first 24 hours after the injury to make sure that no potentially serious symptoms develop. 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.
Injured people are checked for symptoms that indicate brain function could be worsening. These symptoms include persistent or increasing sleepiness and confusion, seizures, 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, noisy breathing, and drainage of clear fluid (cerebrospinal fluid) from the nose or an ear. 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 magnetic resonance imaging (MRI) is done, and any significant injuries of the skull or brain tissue are treated. CT is more accurate for diagnosis of skull fractures, and MRI is more accurate for certain types of brain injuries. Skull x-rays are rarely helpful.
People are admitted to the hospital if doctors suspect brain damage based on symptoms or CT findings. Children are admitted to the hospital for these reasons or if they were unconscious even briefly or had a seizure. Children are also admitted to the hospital if child abuse is suspected.
If the injury may affect other parts of the body (for example, after a motor vehicle crash) or 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.
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 immediately check whether the person is oriented and able to respond to commands. They also determine how much stimulation the person needs before opening the eyes. Doctors next assess basic brain function by checking, for example, 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. 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.
People with severe head injuries are admitted to the hospital, usually to an intensive care unit. The blood pressure and levels of oxygen and carbon dioxide in the blood are kept at desirable levels. 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. Doctors control blood oxygen and carbon dioxide 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. Pain is treated. 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.
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 internal spaces (ventricles) within the brain. The ventricles contain cerebrospinal fluid, which flows over the surface of the brain between the 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 open the skull to relieve the pressure.