Injury to the head may occur as a result of traffic accidents, sports injuries, falls, assault, accidents at work and at home, or bullet wounds. Most people suffer a minor head injury at least once in their lives, but very few of the injuries are severe enough to require treatment. A head injury can damage the scalp, skull, or brain. Minor injuries usually cause no damage to the underlying brain. Even when there is a skull fracture, or the scalp is split, the brain may not be damaged. However, a blow to the head may severely shake the brain, and this can sometimes cause brain damage even when there are no external signs of injury.
A blow often bruises the brain tissue, causing death of some of the brain cells in the injured area. When an object actually penetrates the skull, foreign material and dirt may be implanted into the brain and lead to infection. A blow or a penetrating injury may also tear blood vessels causing brain haemorrhage (bleeding in or around the brain). Head injury may cause swelling of the brain; this is particularly evident after bullet wounds because their high velocity causes extensive damage. If the skull is fractured, bone may be driven into the underlying brain.
Symptoms and signs
If the head injury is mild, there may be no symptoms other than a slight headache. In some cases there is concussion, which may cause confusion, dizziness, and blurred vision (sometimes persisting for several days). More severe head injuries, particularly blows to the head, may result in unconsciousness that lasts longer than a few minutes, or coma (a state of unconsciousness and unresponsiveness to stimuli), which may be fatal.
Post-concussive amnesia (loss of memory of events that occurred after an accident) may occur, especially if the skull has been fractured. This amnesia usually lasts more than an hour after consciousness is regained. There may also be pretraumatic amnesia (loss of memory of events that occurred before the accident). The more serious the injury to the brain, the longer unconsciousness and amnesia are likely to last.
After a severe brain injury, a person may suffer some muscular weakness or paralysis and loss of sensation.
Symptoms such as persistent vomiting, pupils of unequal size, double vision, or a deteriorating level of consciousness suggest progressive brain damage.
Investigations may include skull X-rays and MRI or CT scanning (techniques that produce cross-sectional or three-dimensional images of body structures). A blood clot inside the skull may be life-threatening and requires surgical removal. Severe skull fractures may also require surgery.
Recovery from concussion may take several days. There may be permanent physical or mental disability if the brain has been damaged. Recovery from a major head injury can be a very slow process and there may be signs of progressive improvement for several years after the injury.
Head injury in more detail - non-technical
Injury to the head may damage the scalp, skull, or brain. The most important consequence of head trauma is traumatic brain injury. Head injury may occur either as a closed head injury, such as the head hitting a car’s windshield, or as a penetrating head injury, as when a bullet pierces the skull. Both may cause damage that ranges from mild to profound. Very severe injury can be fatal because of profound brain damage.
External trauma to the head is capable of damaging the brain, even if there is no external evidence of damage. More serious injuries can cause skull fracture, blood clots between the skull and the brain, or bruising and tearing of the brain tissue itself.
Injuries to the head can be caused by traffic accidents, sports injuries, falls, workplace accidents, assaults, or bullets. Most people have had some type of head injury at least once in their lives, but rarely do they require a hospital visit.
Each year about two million people in the US have a serious head injury and up to 750,000 of them are severe enough to require hospitalization. Brain injury is most likely to occur inmales between ages 15 and 24, usually as a result of car and motorcycle accidents. About 70% of all accidental deaths are due to head injuries, as are most of the disabilities that occur after trauma.
A person who has had a head injury and who is experiencing the following symptoms should seek medical care immediately:
- serious bleeding from the head or face
- loss of consciousness, however brief
- confusion and lethargy
- lack of pulse or breathing
- clear fluid drainage from the nose or ear
Causes and symptoms
A head injury may cause damage both from the direct physical injury to the brain and from secondary factors, such as lack of oxygen, brain swelling, and disturbance of blood flow. Both closed and penetrating head injuries can cause swirling movements throughout the brain, tearing nerve fibers and causing widespread bleeding or a blood clot in or around the brain. Swelling may raise pressure within the skull (intracranial pressure) and may block the flow of oxygen to the brain.
Head trauma may cause a concussion, in which there is a brief loss of consciousness without visible structural damage to the brain. In addition to loss of consciousness, initial symptoms of brain injury may include:
- memory loss and confusion
- partial paralysis or numbness
After a head injury, there may be a period of impaired consciousness followed by a period of confusion and impaired memory with disorientation and a breakdown in the ability to store and retrieve new information. Others experience temporary amnesia following head injury that begins with memory loss over a period of weeks, months, or years before the injury (retrograde amnesia). As the patient recovers, memory slowly returns. Post-traumatic amnesia refers to loss of memory for events during and after the accident.
Epilepsy occurs in 2–5% of people who have had a head injury; it is much more common in people who have had severe or penetrating injuries. Most cases of epilepsy appear right after the accident or within the first year and become less likely with increased time following the accident.
Closed head injury
Closed head injury refers to brain injury without any penetrating injury to the brain. It may be the result of a direct blow to the head; of the moving head being rapidly stopped, such as when a person’s head hits a windshield in a car accident; or by the sudden deceleration of the head without its striking another object. The kind of injury the brain receives in a closed head injury is determined by whether or not the head was unrestrained upon impact and the direction, force, and velocity of the blow. If the head is resting on impact, the maximum damage will be found at the impact site. A moving head will cause a ‘‘contrecoup injury’’ where the brain damage occurs on the side opposite the point of impact, as a result of the brain slamming into that side of the skull. A closed head injury also may occur without the head being struck, such as when a person experiences whiplash. This type of injury occurs because the brain is of a different density than the skull and can be injured when delicate brain tissues hit against the rough, jagged inner surface of the skull.
Penetrating head injury
If the skull is fractured, bone fragments may be driven into the brain. Any object that penetrates the skull may implant foreign material and dirt into the brain, leading to an infection.
A skull fracture is a medical emergency that must be treated promptly to prevent possible brain damage. Such an injury may be obvious if blood or bone fragments are visible, but it is possible for a fracture to have occurred without any apparent damage. A skull fracture should be suspected if there is:
- blood or clear fluid leaking from the nose or ears
- unequal pupil size
- bruises or discoloration around the eyes or behind the ears
- swelling or depression of part of the head Intracranial hemorrhage
Bleeding (hemorrhage) inside the skull may accompany a head injury and cause additional damage to the brain. A blood clot (hematoma) may occur if a blood vessel between the skull and the brain ruptures; when the blood leaks out and forms a clot, it can press against brain tissue, causing symptoms from a few hours to a few weeks after the injury. If the clot is located between the bones of the skull and the covering of the brain (dura), it is called an epidural hematoma. If the clot is between the dura and the brain tissue itself, the condition is called a subdural hematoma. In other cases, bleeding may occur deeper inside the brain. This condition is called intracerebral hemorrhage or intracerebral contusion (from the word for bruising).
In any case, if the blood flow is not stopped, it can lead to unconsciousness and death. The symptoms of bleeding within the skull include:
- nausea and vomiting
- loss of consciousness
- unequal pupil size
If the head injury ismild, theremay be no symptoms other than a slight headache. There also may be confusion, dizziness, and blurred vision. While the head injury may seem to have been quite mild, in many cases symptoms persist for days or weeks.Up to 60%of patients who sustain a mild brain injury continue to experience a range of symptoms called ‘‘post-concussion syndrome,’’ as long as six months or a year after the injury.
The symptoms of post-concussion syndrome can result in a puzzling interplay of behavioral, cognitive, and emotional complaints that can be difficult to diagnose, including:
- behavior changes
- memory loss
- cognitive deficits
- emotional outbursts
The extent of damage in a severe head injury can be assessed with computed tomography (CT) scan, magnetic resonance imaging (MRI), positron emission tomography (PET) scans, electroencephalograms (EEG), and routine neurological and neuropsychological evaluations.
Doctors use the Glasgow Coma Scale to evaluate the extent of brain damage based on observing a patient’s ability to open his or her eyes, respond verbally, and respond to stimulation by moving (motor response). Patients can score from 3 to 15 points on this scale. People who score below eight when they are admitted usually have suffered a severe brain injury and will need rehabilitative therapy as they recover. In general, higher scores on the Glasgow Coma Scale indicate less severe brain injury and a better prognosis for recovery.
Patients with a mild head injury who experience symptoms are advisedtoseek out the care of a specialist; unless a family physician is thoroughly familiar with medical literature in this newly emerging area, experts warn that there is a good chance that patient complaints after a mild head injury will be downplayed or dismissed. In the case of mild head injury or post-concussion syndrome, CT and MRI scans, electroencephalograms (EEG), and routine neurological evaluations all may be normal because the damage is so subtle. In many cases, these tests cannot detect the microscopic damage that occurs when fibers are stretched in a mild, diffuse injury. In this type of injury, the axons lose some of their covering and become less efficient. This mild injury to the white matter reduces the quality of communication between different parts or the brain. A PET scan, which evaluates cerebral blood flow and brain metabolism, may be of help in diagnosing mild head injury.
Patients with continuing symptoms after a mild head injury should call a local chapter of a head-injury foundation that can refer patients to the best nearby expert.
If a concussion, bleeding inside the skull, or skull fracture is suspected, the patient should be kept quiet in a darkened room, with head and shoulders raised slightly on a pillow or blanket.
After initial emergency treatment, a team of specialists may be needed to evaluate and treat the problems that result. A penetrating wound may require surgery. Those with severe injuries or with a deteriorating level of consciousness may be kept hospitalized for observation. If there is bleeding inside the skull, the blood may need to be surgically drained; if a clot has formed, it may need to be removed. Severe skull fractures also require surgery.
Supportive care and specific treatments may be required if the patient experiences further complications. People who experience seizures, for example, may be given anticonvulsant drugs, and people who develop fluid on the brain (hydrocephalus) may have a shunt inserted to drain the fluid.
In the event of long-term disability as a result of head injury, there are a variety of treatment programs available, including long-term rehabilitation, coma treatment centers, transitional living programs, behavior management programs, life-long residential or day treatment programs and independent living programs.
Prompt, proper diagnosis and treatment can help alleviate some of the problems after a head injury. It usually is difficult to predict the outcome of a brain injury in the first few hours or days; a patient’s prognosismay not be knownformanymonths or even years.
The outlook for someone with a minor head injury generally is good, although recovery may be delayed and symptoms such as headache, dizziness, and cognitive problems can persist for up to a year or longer after an accident. This can limit a person’s ability to work and cause strain in personal relationships.
Serious head injuries can be devastating, producing permanent mental and physical disability. Epileptic seizures may occur after a severe head injury, especially a penetrating brain injury, a severe skull fracture, or a serious brain hemorrhage. Recovery from a severe head injury can be very slow, and it may take five years or longer to heal completely. Risk factors associated with an increased likelihood of memory problems or seizures after head injury include age, length and depth of coma, duration of post-traumatic and retrograde amnesia, presence of focal brain injuries, and initial Glasgow Coma Scale score.
As researchers learn more about the long-term effects of head injuries, they have started to uncover links to later conditions. A 2003 report found that mild brain injury during childhood could speed up expression of schizophrenia in those who were already likely to get the disorder because of genetics. Those with a history of a childhood brain injury, even a minor one, were more likely to get familial schizophrenia than a sibling and to have earlier onset. Another study in 2003 found that people who had a history of a severe head injury were four times more likely to develop Parkinson’s disease than the average population. Those requiring hospitalization for their head injuries were 11 times as likely. The risk did not increase for people receiving mild head injuries.
Many severe head injuries could be prevented by wearing protective helmets during certain sports or when riding a bike or motorcycle. Seat belts and airbags can prevent many head injuries that result from car accidents. Appropriate protective headgear always should be worn on the job where head injuries are a possibility.