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Traumatic brain injury (TBI) represents a significant global public health problem. In the United States, estimates of the frequency of TBI range between 2.5 and 4 million cases per year, depending on the study and methods used to define and include cases. Age-specific rates show a bimodal distribution, with highest risk in younger individuals and older adults. The most common mechanism of injury in the young is motor vehicle accidents and is more common in men, whereas in older adults, falls are the major cause of injury and are more likely to occur in women.
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TBI imposes substantial demands on health care systems. Worldwide, at least 10 million TBIs are serious enough to result in death or hospitalization, producing a global economic burden of $400 billion annually. In the United States, the estimated annual cost is >$76 billion. Due to advances in medical care and other factors, more people are surviving TBI than ever before. Brain injury accounts for more lost productivity at work among Americans than any other form of injury. An estimated 5.3 million Americans are living with significant disabilities resulting from TBI that complicate their return to a full and productive life. Increased media attention to military and sports-related TBI has highlighted the growing concern that injuries that were previously dismissed can have lifelong consequences for some individuals.
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Head injuries are so common that almost all physicians will be called upon to provide some aspect of immediate care or to see patients who are suffering from various sequelae. Patients and their families initially need education regarding the natural history of TBI along with treatment of acute symptoms such as headache. Continued follow-up is important to ensure that the sequelae experienced by some patients—such as postconcussive disorder (PCD), depression, or sleep disorder—are identified and treated appropriately. Effective management of TBI and its consequences often requires a coordinated multidisciplinary care team.
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DEFINITION AND CLASSIFICATION
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TBI is commonly defined as an alteration in brain function, or other evidence of brain pathology, caused by an external force, and characterized by the following: (1) any period of loss or decreased level of consciousness (LOC), (2) any loss of memory for events immediately before (retrograde) or after (posttraumatic) the injury, (3) any neurologic deficits, and/or (4) any alteration in mental state at the time of injury.
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Evidence of TBI can include visual, neuroradiologic, or laboratory confirmation of damage to the brain, but TBI is more often diagnosed on the basis of acute clinical criteria. In addition to standard CT imaging, structural MRI and functional imaging (resting-state functional MRI) techniques show increasing sensitivity, and it is likely that sensitive blood-based biomarkers will play an increasingly important role in the diagnosis and treatment of these patients (described below).
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Common mechanisms of TBI include the head being struck ...