Head trauma and the resulting brain injuries are one of the leading causes of death and disability in the industrialized world. In the United States, more than 50,000 people die every year as a result of traumatic brain injury. Furthermore, it is estimated that a head injury occurs every seven seconds, and hospital emergency rooms treat 1 million people for brain injuries every year. Currently about 5.3 million Americans — a little more than 2 percent of the U.S. population — live with disabilities resulting from such injuries.
Traumatic brain injury may occur at any age, but the peak incidence is among people between the ages of 15 and 24. Men are affected three to four times more often than women. Motor vehicle accidents are the leading cause, accounting for approximately 50 percent of all cases. Falls produce the most brain injuries in people older than 60 and younger than 5. Other causes include violent assault and firearms misuse. It has been estimated that after one brain injury, the risk of a second injury is three times greater, and that after a second injury, the risk of a third is eight times greater.
There are many head injury symptoms, ranging in seriousness. Minor injuries will cause mild or no symptoms, while severe injuries will cause major derangement of function. The most common symptom of brain injury after head trauma is a disturbance of consciousness; some people remain awake, but others are confused, disoriented, or unconscious. Headache, nausea, and vomiting are other common symptoms.
Anyone who sustains a head injury should be examined by a physician. Symptoms of brain trauma can be initially subtle, seemingly unrelated to the head, and not immediately apparent. A person who has sustained a serious head injury should not be manipulated or moved by people who are not trained to do so, because this may aggravate an injury.
Diagnosing Brain Trauma
The first thing doctors do when assessing a head injury is determine whether the person is in imminent danger of death. Once the person’s vital functions are stabilized, physicians examine the individual from a neurological perspective, checking:
- level of consciousness
- function of the cranial nerves (through pupillary responses to light, eye movements, and facial symmetry)
- motor function (strength, symmetry, and any abnormality of movements)
- breathing rate and pattern (linked to brain stem function)
- deep tendon reflexes, such as the knee jerk
- sensory function, such as response to a pinprick
- external signs of trauma, fracture, deformity, and bruising in the head and neck
Each of these parts of the physical exam will give a physician clues about the extent and location of any brain injury.
Doctors also need to know about the person’s behavior before, during, and after the injury. All of these points yield clues about what might have happened and how best to treat the person. Family members or people who witnessed the accident can usually provide helpful information. They can help medical professionals provide the best care possible by taking note of certain symptoms:
- unusual sleepiness or difficulty awakening
- mental confusion
- vomiting that continues or worsens
- restlessness or agitation that continues or worsens
- stiff neck
- unequal pupil size or peculiar eye movements
- inability to move arms and legs on either side
- clear or bloody drainage from the ears or nose
- bruising around the eyes or behind the ears
- difficulty breathing
This is a partial list.
Physicians can use a variety of radiological tests to assess a person with head trauma. Most hospital emergency departments can now do computed tomography (CT) scans. CT provides more information, and is excellent for diagnosing skull fractures, bleeding, or other important lesions in the brain. CT also helps doctors follow people with head trauma as they recover. Magnetic resonance imaging (MRI) currently has little involvement in diagnosing and treating an emergency, but once a person’s condition is stable an MRI may provide useful information that a CT cannot, such as evidence of white matter damage.
Different types of injuries require particular treatments. Surgery is needed to remove blood or foreign material, or to reconstruct parts of the skull. Very often brain trauma causes tissue to swell against the inflexible bone. In these cases, a neurosurgeon may relieve the pressure inside the skull by placing a ventriculostomy drain that removes cerebrospinal fluid. If the swelling is massive, a neurosurgeon may remove a piece of the skull so that the brain has room to expand; the surgeon keeps and reimplants the bone after the swelling has gone down significantly. Often during these procedures, the surgeon places a small pressure valve inside the skull to measure pressure on a moment-to-moment basis.
Most nonsurgical management of brain trauma involves close monitoring, often in an intensive care unit, to prevent further injury. Physicians will conduct further neurological exams in order to assess whether the person is improving or worsening. Doctors have no “miracle drug” to prevent nerve injury or improve brain function immediately after trauma, but they can use medication to modify a person’s blood pressure, optimize the delivery of oxygen to the brain tissue, and prevent further brain swelling.
Specific Injuries in Head Trauma
Trauma to the head can produce many problems because so many components may be injured. Brain tissue is surrounded both by the skull and by a tough membrane called the dura, which is right next to the brain. Within, and surrounding, the brain tissue and dura are many arteries, veins, and important nerves (the cranial nerves). Therefore, trauma to the head may damage the skull, the blood vessels, the nerves, the brain tissue itself, or all of the above. Depending on the nature and severity of their injuries, people may exhibit a very wide range of symptoms: from absolutely none to coma.
Injuries to the Skull
Fractures of the skull can be divided into linear fractures, depressed fractures, and compound fractures. Linear fractures are simple “cracks” in the skull. Most require no treatment. The concern with these fractures is that a force large enough to break the skull may have damaged the underlying brain or blood vessels. This is especially true for fractures of the bottom, or “base,” of the skull.
Depressed skull fractures are those in which part of the bone presses on or into the brain. The extent of the damage depends on what part of the brain the depressed skull overlies, as well as the nature of any associated injuries to other tissues.
In compound fractures, the trauma is severe enough to break the skin, bone, and dura and expose the brain tissue. These types of fractures are usually associated with severe brain damage.
Treating skull fractures depends on the extent of damage to structures beneath the bone. Most linear fractures will not damage other structures unless the fractured bone becomes displaced and presses on the brain. In this case a surgical repair may be necessary to restore the bone to its normal position. Depressed skull fractures are usually also treated surgically in order to restore normal anatomy and prevent damage to underlying tissues by bone fragments.
Compound fractures are a special case since, by definition, there has been contact between the brain tissue and the outside air. These fractures therefore bring the possibility of infection from environmental debris. The fracture site is therefore vigorously cleaned and decontaminated before repair. In addition, these fractures are usually associated with severe injuries to the brain, blood vessels, and nerves, and repairing these structures may also be necessary.
Injuries Involving Vessels
Injuries to the blood vessels within the skull may lead to the collecting of blood in abnormal places. A collection of blood outside a vessel is called a hematoma. In all of the following types of hematomas, individuals are in danger if there is enough accumulating blood to press on the brain or other important structures within the skull. (In this respect, a head injury can resemble a hemorrhagic stroke.) In these cases, the hematoma may compress the brain and shift it from its normal position. Too much shifting can damage the crucial brain stem. Bleeding may also raise the pressure inside the skull to the point that it shuts off the blood supply to the brain (as in an ischemic stroke. These conditions can be very serious and require emergency surgery.
Epidural hematomas occur between the skull and the dura. These are usually caused by a direct impact injury that causes a forceful deformity of the skull. Eighty percent are associated with skull fractures across an artery called the middle meningeal artery. Because arteries bleed quickly, this type of injury can cause significant bleeding within the skull and require emergency surgery. Although uncommon (affecting only 0.5 percent of all head-injured individuals), epidural hematomas are a surgical emergency, and people with this type of injury must have the damage immediately repaired in the operating room.
Subdural hematomas appear between the dura and the surface of the brain. These are more common than epidural hematomas, occurring in about 30 percent of people with severe head trauma. They are produced by the rupture of small veins, so the bleeding is much slower than in epidural hematomas. A person with a subdural may have no immediate symptoms. As blood slowly collects within the skull, however, it compresses the brain and increases the intracranial pressure.
There are three types: acute, subacute, and chronic. The acute subdural may cause drowsiness or coma within a few hours and requires urgent treatment. A subacute subdural should be removed within one to two weeks. The most treacherous is a chronic subdural hematoma. It is not uncommon for such an injury to go undiagnosed for several weeks because individuals or their families do not recognize subtle symptoms. A person may appear well but nonetheless have a large subdural. That is why it is important for a heath professional to evaluate all individuals with head injuries. Depending on the symptoms and size of the subdural, treatment may involve careful monitoring or surgical removal of the blood.
Scans should be done on any person with prolonged headaches or other symptoms after head injury.
Intracerebral hematoma. Injuries to small blood vessels in the brain may also lead to bleeding within the brain tissue, called an intracerebral hematoma. The effect of this hematoma depends on how much blood collects, and where, and whether the bleeding continues. Doctors may respond conservatively, finding no need for treatment, or treat the problem as an emergency. More than half of people with intracerebral hematomas lose consciousness at the time of injury. There may be associated brain contusions with this hematoma.
Subarachnoid hemorrhage. Bleeding may occur in a thin layer immediately surrounding the brain (the subarachnoid space). In head trauma, it is common to have some degree of subarachnoid hemorrhage, depending on the force applied to the head. In fact, subarachnoid hemorrhage is the most commonly diagnosed abnormality after head trauma. CT detects it in 44 percent of severe head trauma cases. Fortunately, individuals with subarachnoid hemorrhage but no other associated injuries usually do very well. However, they may get delayed hydrocephalus as a result of blockage of the flow of cerebrospinal fluid.
Injuries to the Brain Tissue
Our brains are somewhat mobile inside our skulls, which can give rise to other injuries. There are some spiny contours on the inside of the skull, but under normal circumstances a barrier of cerebrospinal fluid surrounds the brain and cushions it from direct contact with the hard bone. However, when a person’s head is subjected to violent forces, the brain may be forcibly rotated and battered within the skull. During such episodes brain tissue may be ripped, stretched, battered, and bruised. Bleeding, swelling, and further bruising of brain tissue usually follows. In these cases, people usually sustain permanent damage.
Injuries to the brain are classified according to the degree of tissue damage that they cause. It is important to remember that the different types of brain injuries are part of a spectrum. There may not be a clear distinction in every case, and one person may suffer multiple types of injuries.
Concussion. A concussion is a temporary and fully reversible loss of brain function caused by direct injury to the brain. It is the mildest form of brain injury, usually resulting from minor trauma to the head. In concussions, it is not possible to identify any structural damage to the brain tissue.
Contusion. Contusions are localized areas of “bruising” of the brain tissue. They consist of areas of swollen brain and blood that has leaked out of small arteries, veins, or capillaries. Contusions will often occur under the impact point on the skull (coup). They may also, in the same incident, occur on the side directly opposite the impact because the brain may rock away from the blow and strike the inside of the skull (contrecoup). Sometimes the skull is broken at the site of a contusion, but not always. Whatever the cause, contusions are likely to be most severe in the tips of the frontal and temporal lobes, after trauma forces these areas of the brain against bony ridges inside the skull.
Lacerations. Lacerations are actual tears in the brain tissue. They can be caused by shear forces placed on the brain, or by an object (such as a bullet) penetrating the skull and brain. The degree of damage depends on the depth and location of the laceration, as well as on whether associated blood vessels and cranial nerves suffer damage.
Diffuse axonal injury. Diffuse axonal injury (DAI) refers to impaired function and eventual loss of axons (the long extensions of nerve cells, which enable them to communicate with one another). It is caused by the acceleration, deceleration, and rotation of the head during trauma, as in a car crash, probably the most frequent cause of this type of injury. These forces can stretch and shear axons. DAI is a microscopic injury that does not show up on a CT scan. Therefore, diagnosing DAI depends on physicians’ observations. Individuals with this sort of injury are usually unconscious for longer than six hours and, depending on the degree and location of axonal injury, may remain this way for days or weeks. DAI may be mild and reversible or, if extensive, may lead to severe brain damage or death. This is the most common cause of injury from high-velocity trauma and has no treatment.
Brain swelling and ischemia. Often, a person’s immediate injury may not be the worst. Usually, there is additional secondary injury to the brain that occurs hours to days later. The damage to the brain tissue, blood vessels, and nerves causes the brain to swell. If that swelling is severe, the blood supply to the brain may be blocked (ischemia), leading to tissue death. Also, since the brain is encased in a hard skull, the swelling may actually compress the tissue against bone. Excessive compression of areas such as the brain stem, which is responsible for regulating our breathing and consciousness (among other vital functions), can lead to severe disability and death.
Perhaps the most widely used system to predict outcome after head injury is the Glasgow Coma Scale (GCS). The individual is evaluated in each of three parameters, and the sum of the three parts provides the total score.
People with mild head injury, usually defined as Glasgow Coma Score 13–15, tend to do very well. These individuals have often suffered concussions or minor degrees of brain swelling or contusion. Although headaches, dizziness, irritability, or similar symptoms may sometimes trouble them, most suffer no residual effects. For people with a simple concussion, the mortality rate is zero. Of people with mild brain swelling, fewer than 2 percent die.
People with moderate head injuries (GCS 9–12) do less well. Approximately 60 percent will make a good recovery, and another 25 percent or so will have moderate degrees of disability. Death or persistent vegetative state (PVS) will be the outcome for 7 percent to 10 percent. The remainder are usually left with severe disability.
People with severe head injuries (GCS under 8) have the worst prognoses. About 25 percent to 30 percent of these individuals have good long-term outcomes, 17 percent have moderate to severe disabilities, and 30 percent die. A small percentage remain in PVS.
In penetrating head injuries, such as those inflicted by bullets, the statistics are a bit different. Over half of all people with gunshot wounds to the head who are alive when they arrive at a hospital later die because their initial injuries are so severe. But the other half, with more mild injuries, usually do fairly well.
The outcome for people in coma after brain injury depends in part on their age. People under 20 are three times more likely to survive than those over 60. One study found that people who showed no motor response to painful stimuli and no pupillary response to light (normally our pupils get smaller when light is shone on them) 24 hours after brain injury were likely to die. However, the presence of both of these responses was a very positive finding, especially in young people.
Rehabilitation After Brain Injury
People who have suffered head trauma and resultant brain injury will often benefit from some physical therapy during their hospital stay or after they leave the hospital. If they are not acutely ill, moving to a rehabilitation program may speed any further recovery. These centers usually teach individuals strategies for reaching the maximum level of functioning their impairments allow. People sometimes have to relearn skills essential for everyday activities. Another major goal of these centers is to work with families to educate them about realistic future expectations and how they can best help their injured family member.
After brain trauma, individuals may have persistent cognitive or emotional disabilities that include:
- short-term memory loss
- long-term memory loss
- slowed ability to process information
- trouble concentrating or paying attention for periods of time
- difficulty keeping up with a conversation
- problems finding words
- spatial disorientation
- organizational problems and impaired judgment
- inability to do more than one thing at a time
Physical consequences can include:
- muscle weakness or spasticity
- double vision or impaired vision
- loss of smell or taste
- speech impairments such as slow or slurred speech
- headaches or migraines
- fatigue, increased need for sleep
- balance problems
Long-term recovery from brain injuries depends on many factors, including the severity of the trauma, associated injuries, and a person’s age. Unlike in the movies, people rarely recover their preinjury level of functioning after severe head trauma. Rather than emphasizing complete recovery, treatment aims to improve function, prevent further injury, and rehabilitate individuals and their families physically and emotionally.
About Peter M. Black
Peter M. Black, M.D., Ph.D., is Chief of Neurosurgery at Children's Hospital/Brigham and Women's Hospital, Harvard University
About Patricio C. Gargollo
Patricio C. Gargollo, M.D., is a urologist, instructor of surgery at Harvard Medical School, and a fellow in pediatric urology at Children's Hospital Boston.
About Adam C. Lipson
Adam C. Lipson, M.D., is Resident Physician, Department of Neurological Surgery, University of Washington Medical Center, Seattle
From the Dana Foundation. Used with permission. www.dana.org.