Chapter 19: Traumatic Brain Injury

TRAUMATIC BRAIN INJURY

Traumatic brain injury (TBI) remains frustratingly resistant to the advances that have improved outcome from so many other types of injury. Recent progress in resuscitation, hemostasis, imaging, noninvasive management, critical care, rehabilitation, and emergency medical system organization has not yet had a significant impact on reducing the toll of this disease. New and developing insights into our classification and approach to TBI may soon pave the way for meaningful advances. Until then, the clinicians who care for these patients must keep themselves as informed as possible about the limitations and appropriate uses of existing therapies.

TBI has been defined in many different ways. A good working definition is that it is a disruption or alteration of brain structure or function caused by external mechanical forces. The disruption may be variable in severity and may be transient or permanent. The causative external forces are diverse and include rapid acceleration or deceleration, direct compression, penetration and physical disruption of brain tissue, blast and other complex mechanisms, and various combinations of these and other etiologies. Mild TBI may be present with no abnormalities on imaging studies. At the other end of the spectrum, more severe injuries may be associated with large contusions, traumatic hematomas, or other immediately life-threatening structural lesions.

EPIDEMIOLOGY

The exact number of people who sustain TBI is unknown since some patients with severe systemic injuries do not survive long enough to undergo a thorough evaluation that would uncover the presence of brain injury. At the other end of the spectrum, many individuals suffering mild or moderate TBI choose not to seek medical care.

Many epidemiologic studies include only those TBI patients who receive medical care in an emergency department. By this criterion, approximately 1.4 million people per year suffer TBI in the United States. Approximately 1.1 million are treated and released, 240,000 are hospitalized, and 50,000 die.¹

Common causes of TBI include falls, motor vehicle collisions (MVCs), pedestrian impact, and assault. TBI has a bimodal age distribution, with the greatest risk in 0–4 and 15- to 19-year-olds. Falls predominate at the extremes of age, whereas MVCs are most common in teenagers and young adults. The incidence in males is 1.5-fold higher than in females. The youngest patients are often the victim of abuse and cannot protect themselves. Military personnel comprise a statistically small number of the overall volume of TBI patients, but combat operations cause them to have a higher incidence of penetrating and blast injuries.

TYPES OF INJURY

Classification and Management

Primary versus Secondary Injury

TBI is a dynamic process. Management priorities for a given patient may change rapidly as his or her underlying pathophysiology changes. Primary injuries result directly from the forces imparted at the time of the accident. These may ...