Section 6. Brain, Spinal Cord, and Nerve Disorders

Chapter 87. Head Injuries

Topics: Introduction | Skull Fracture | Concussion | Cerebral Contusions and Lacerations | Intracranial Hematomas

Introduction

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, and most head injuries are minor.

Nonetheless, some head injuries are serious. Head injuries kill and disable more people younger than 50 than does any other type of neurologic damage. Head injuries occur in more than 70% of motor vehicle accidents, which are the leading cause of death in males younger than 35. Nearly 50% of people who have a severe head injury die.

About half of head injuries result from motor vehicle accidents. Other common causes are falls in the home, physical assaults, and accidents during sports, during recreational activities, or in the workplace (for example, while operating machinery).

Head injuries include external injury to the scalp, skull fractures, concussions, bruises (contusions) and tears (lacerations) of the brain, and accumulation of blood within the brain or between the brain and skull (intracranial hematoma). The brain can be damaged even if the skull is not fractured. Often, the severity of brain damage does not correlate with the severity of external injuries.

Symptoms

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.

After a concussion, consciousness may be lost, usually for less than 15 minutes. A bump may appear on the head, and headache, dizziness, nausea, and vomiting may occur. Usually, such symptoms resolve in days to weeks. Sometimes after a head injury, even a minor one, symptoms persist for a considerable time. Symptoms that persist are called the postconcussion syndrome (see Section 6, Chapter 87).

Certain symptoms indicate that the head injury is serious and that brain function is worsening. They include increasing sleepiness and confusion, vomiting that persists, 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, increasing blood pressure, slowing pulse, and drainage of clear fluid (cerebrospinal fluid) from the nose or mouth. These symptoms may develop hours or sometimes days after the original injury. Health care practitioners tell people who have a head injury what symptoms to watch for. Parents of small children are told how to monitor their children for these symptoms during the hours after an injury. If these symptoms occur, prompt medical attention is essential.

See the figure Herniation: The Brain Under Pressure.

Symptoms of worsening brain function occur because pressure within the skull is increased. For example, pressure increases when blood vessels and tissues in or around the brain are torn, allowing blood and fluid to leak out. The result is accumulation of blood (hematoma) or of fluid (edema) and swelling. Pressure increases because the skull cannot expand to accommodate the increase in its contents. Increased pressure can damage or destroy brain tissue, causing loss of various functions, depending on which area of the brain is damaged (see Section 6, Chapter 82). Increased pressure within the skull 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 be life threatening if pressure is put on the brain stem, the lower part of the brain, which controls such vital functions as heart rate and breathing. Unconsciousness, coma, and even death may result.

See the sidebar Recognizing a Serious Head Injury.

Posttraumatic epilepsy may occur months to years (usually not more than 4 years) after the brain is damaged by a severe head injury. Seizures (see Section 6, Chapter 85) occur in about 70% of people who have had a severe head injury with penetration of the brain and in about 5 to 30% of those who have had a severe head injury without penetration of the brain. Symptoms often depend on where in the brain the seizure originates. For example, seizures originating in the frontal lobe cause twitches in specific muscles of the limbs on the opposite side of the body.

Prognosis

Most people who develop symptoms after a minor head injury recover completely within a few days.

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 disability of varying degrees to death. The type and severity of disabilities depend on where and how badly the brain was damaged. 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 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.

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 permanent disability. Nonetheless, rehabilitation can help people minimize the effect of disabilities on function (see Section 1, Chapter 7).

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.

Diagnosis and Treatment

If a head injury is minor and causes no symptoms other than pain at the site of injury, acetaminophen (see Section 6, Chapter 78) (but not aspirin or any other nonsteroidal anti-inflammatory drug) may be taken. Applying cold compresses may also help relieve pain. Having another person check in with the injured person for a few hours to make sure that no symptoms develop is advisable. Children who have had a minor head injury may be allowed to sleep, but they should be awakened at regular intervals to make sure they can be aroused. The length of the interval (ranging from every 2 to 4 hours) depends on the relative severity of the injury and the appearance and behavior of the child.

If a head injury causes loss of consciousness, even briefly, or if symptoms of worsening brain function develop, immediate evaluation by a doctor is necessary.

If head injury is traumatic (for example, due to a motor vehicle accident) 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. If the head injury was severe enough to cause loss of consciousness, the neck is assumed to be broken until proved otherwise. In such cases, the person's head, neck, and spine are stabilized. Usually, the person is strapped to a firm board and carefully padded to prevent movement.

When the person reaches the hospital, doctors and nurses perform a physical examination to determine whether the injury is serious. First, they check vital signs: heart rate, blood pressure, and breathing. A person who is not breathing adequately may need a ventilator. Level of consciousness, memory, and ability to use language are immediately assessed (see Section 6, Chapter 77). Basic brain function is evaluated by checking the size of the pupils and their reaction to light, by evaluating the response to sensations such as heat or pinpricks, and by testing the ability to move the arms and legs. Computed tomography (CT) or magnetic resonance imaging (MRI) is performed to check for possible brain damage. Standard x-rays can identify skull fractures but reveal very little about brain damage. These procedures are also used to determine whether the neck is broken.

If the head injury is severe and the person's condition is worsening, mannitol is usually given intravenously to reduce swelling (which can develop quickly) and thus reduce pressure within the skull. Mannitol draws fluid from the brain and promotes urine excretion. Sometimes corticosteroids are given intravenously to reduce swelling. A small pressure gauge may be implanted inside the skull to measure pressure within the skull and to determine how well the treatments are working. 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.

If a head injury is severe, most doctors recommend giving an anticonvulsant (such as phenytoin, carbamazepine, or valproate (see Section 6, Chapter 85)) for up to 2 weeks to prevent seizures. If no seizures occur, the anticonvulsant is stopped. If a seizure occurs, the anticonvulsant is continued for several years or indefinitely.

See the sidebar Head Injuries in Children.