HEAD TRAUMA

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CHAPTER 103 HEAD TRAUMA

Traumatic brain injury (TBI) is a major cause of death and disability in the United States and many other parts of the world. An estimated 1.5 million people sustain a TBI each year in the United States. There are 50,000 deaths from TBI, which accounts for one third of all injury-related deaths. Among TBI survivors, more than 200,000 require hospitalization, and 80,000 to 90,000 experience the onset of a long-term or lifelong disability associated with a TBI. The social and economic costs related to TBI are enormous. Direct and indirect costs of TBI were estimated to be $56.3 billion in 1995. These statistics indicate that TBI is a major public health problem with significant socioeconomic implications.

The leading causes of TBI are motor vehicle accidents, gunshot wounds and other types of physical assault, and falls. TBI also occurs in a wide variety of athletic activities. Approximately 300,000 sports-related TBIs occur each year in the United States.

Boys and men are twice as likely as girls and women to sustain a TBI. Individuals 15 to 24 years of age and those older than 75 constitute the two age groups at highest risk for TBI.

TRAUMA CARE SYSTEMS

The development of organized trauma care systems has also played a role in improving the outcomes of patients with TBI and other injuries. These systems, which have been introduced in the United States since the late 1970s, have been shown to decrease mortality after major trauma.1 The most advanced of these is the level 1 trauma center, which maintains trauma surgeons and anesthesiologists in the hospital 24 hours per day and ready access to trauma surgical suites. Neurosurgeons and other specialists are immediately available as needed. The next echelon is the level 2 trauma center, which has immediate access to surgeons and anesthesiologists but does not maintain in-house physician staffing. A level 2 center is able to initiate definitive care for all injured patients but may have to refer some tertiary trauma care needs to a level 1 center. Some cities also have specialized pediatric trauma centers.

TRAUMATIC BRAIN INJURY CLASSIFICATION

TBI is a very common problem with a wide spectrum of severity. Both clinical examination and radiographic imaging are essential components of the optimal evaluation of these patients.

Glasgow Coma Scale and Glasgow Outcome Scale

A simple and reliable clinical assessment tool is needed for evaluating acute TBI. An accurate baseline assessment is crucial, and serial assessments are also needed, because neurological status may change with time, sometimes rapidly. TBI care is provided by a wide range of physicians, nurses, and allied health personnel. Many classification schemes have been developed; however, the Glasgow Coma Scale (GCS) (Table 103-1), introduced by Teasdale and Jennett in 1974, is the most widely used.2 The GCS has proved to be accurate, capable of detecting clinically important changes in neurological status, and easy to use by a variety of health care professionals.

TABLE 103-1 The Glasgow Coma Scale

Activity Score Performance
Eye opening
  4 Spontaneously
3 In response to voice
2 In response to pain
1 None
Best verbal response
  5 Oriented
4 Confused
3 Inappropriate words
2 Incomprehensible sounds
1 None
Best motor response
  6 Follows commands
5 Localizes to pain
4 Withdraws in response to pain
3 Abnormal flexion in response to pain
2 Abnormal extension in response to pain
1 None

Total score ranges from 3 to 15.

Scores on the GCS range from 3 to 15. A GCS score of 3 to 8 is indicative of severe head injury, with a mortality rate of 35% to 40%. A GCS score of 9 to 12 is indicative of moderate head injury, with a mortality rate of 5% to 10%, and a score of 13 to 15 is indicative of mild head injury, with a mortality rate of less than 2%. Children older than 2 years and teenagers have a better prognosis than do adults. The postresuscitation GCS is one of the strongest predictors of ultimate outcome after TBI.

For example, a patient who opens eyes only in response to pain, has a best motor response of abnormal flexion to pain, and a best verbal response of incomprehensible sounds would receive 2 points for eye opening, 3 points for motor response, and 2 points for verbal response. The GCS score would therefore be 7, in the severe TBI category.

The GCS cannot be used reliably in patients younger than 2 years, because children in that age group are not able to carry out the normal motor and verbal responses required by the test. Various pediatric head injury scales have been proposed, but none has been widely adopted.

A reliable scale is also needed to assess the long-term outcomes of patients as they recover from TBI. The Glasgow Outcome Scale (Table 103-2) is a commonly used system that has been developed for this purpose. Serial testing indicates that more than two thirds of patients reach their final outcome category on the Glasgow Outcome Scale within 3 months of injury.

TABLE 103-2 The Glasgow Outcome Scale

Outcome Category Definition
Good recovery Patient able to return to former occupation, although not necessarily at the same level; may have minor neurological or psychological impairments
Moderate disability Patient unable to return to work but otherwise able to perform the activities of daily living independently
Severe disability Patient requires assistance to perform daily activities and cannot live independently
Persistent vegetative Absence of speech or no evidence of mental function in a patient who appears awake with spontaneous eye opening
Death  

IMAGING OF TRAUMATIC BRAIN INJURY

Computed tomography (CT) has revolutionized the imaging of patients with acute TBI. Since its introduction in the 1970s, the procedure has become much faster, and image quality has improved dramatically. On a modern scanner, each image is acquired in less than a second, and an entire head examination can be completed in less than a minute. CT has replaced plain skull radiography and angiography as the primary imaging modality in acute TBI.

CT provides a very detailed look at the brain parenchyma, skull, and extracranial soft tissues and is very accurate in the diagnosis of important sequelae of TBI, including intracranial hematoma, midline shift, cerebral edema, pneumocephalus, and skull fracture.

Magnetic resonance imaging (MRI) is less useful in evaluating acute head injury, because scanning times are longer and because it is more difficult to perform in patients who are agitated and combative and in patients on mechanical ventilation. For these reasons, MRI is generally not performed in the setting of acute TBI. MRI may be useful in selected cases, such as when the patient is unconscious but CT yields normal or unremarkable findings. In these situations, MRI may reveal evidence of diffuse axonal injury or a brainstem injury that was not seen on CT.

The clinical severity of TBI is not always correlated with the magnitude of findings seen on CT. For example, in a patient with clinically mild TBI, an intracranial hematoma may be apparent on the admitting computed tomographic scan. With modern high-resolution scanning techniques, head CT displays abnormal findings in up to 50% of cases of mild TBI.3 Conversely, a patient, who is deeply unconscious with a severe TBI, may undergo initial head CT that yields completely normal findings. This underscores the fact that the clinician cannot rely solely on clinical findings or on results of CT when evaluating patients with TBI. The clinical and imaging examinations are complementary, and both are needed for the optimal evaluation of patients with TBI.

SPECIFIC INJURIES

Concussion

The most common head injury is concussion, also known as mild traumatic brain injury. The hallmark of concussion is an alteration of consciousness as a result of nonpenetrating injury to the brain. There is often a period of amnesia for the event, and recovery is generally rapid. Aside from altered mental status, the neurological examination yields normal findings. Results of CT and MRI of the brain are normal.

No specific treatment for concussion is required. Prognosis is excellent, and a full recovery may be expected in most cases. Patients are allowed to return to their usual activities as their symptoms resolve.

Two complications of concussion warrant further discussion. First, it is now believed that the effects of repeated concussion are cumulative and can lead to the development of chronic dementia. The “punch drunk” syndrome that occurs in professional boxers exemplifies this phenomenon.

Another serious complication of seemingly mild head injury is the second-impact syndrome, a rare condition that has been described in athletes who sustain a second head injury while still symptomatic from an earlier injury. Although the individual appears to have only minimal impairment from the first injury, malignant cerebral edema, which is refractory to all interventions, occurs soon after the second injury. The mortality rate with second-impact syndrome is 50% to 100%. Recognition and increasing understanding of this syndrome have led to the development of guidelines that allow for a safe return to athletic competition while avoiding the devastating complications of second-impact syndrome. In addition to neurological examination and imaging studies, neuropsychological testing is now an important part of the decision-making process for allowing athletes to return to competition after TBI (Bailes, Day, 2001).4

Contusion

Cerebral contusion is the classic example of focal TBI. In the pre-CT era, cerebral contusion could be diagnosed only in the operating room during craniotomy or at the autopsy table. Thus, contusion was considered only in cases of severe TBI and was therefore thought to be pathognomonic for severe injury. Since the advent of CT, especially current high-resolution techniques, contusions have commonly been observed in patients with clinically mild and moderate TBI. It is now recognized that there is a wide range of severity associated with cerebral contusion. Tiny punctate contusions in patients with mild TBI have little or no clinical significance and carry the same prognosis as normal findings on CT.5 At the other end of the spectrum, large contusions with significant mass effect in patients with severe TBI can be life-threatening.

Contusions can be classified as coup or contrecoup injuries. Coup contusions occur at the location of impact, whereas contrecoup contusions occur on the opposite side or at a point distant from the impact. Contusions may be present in any part of the brain but are most common in the frontal and temporal lobes. Figure 103-1 shows a typical hemorrhagic contusion in the left inferior frontal region, just above the roof of the orbit.

Contusions often enlarge during the first week after injury. Repeated CT should be considered if the patient exhibits clinical deterioration. Surgery may be necessary to resect areas of contused brain if there is significant mass effect with raised ICP. Temporal lobe contusions are particularly ominous because of their proximity to the brainstem and risk of herniation.

Subdural Hematoma

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