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Traumatic brain injury (TBI) is defined as impairment in brain function as a result of mechanical force. The dysfunction can be temporary or permanent, and may or may not result in underlying structural changes in the brain. The clinical severity ranges from very mild (dazed or momentarily stunned) to profoundly impaired (unresponsive, comatose). TBI is classified based on the clinical assessment of a patient’s level of consciousness with little or no regard to the actual underlying injury. Therefore, patients with the same TBI severity classification may have a dramatically different pathophysiology (Figure 254-1). The current classification system, based on the Glasgow Coma Scale (GCS), divides TBI into severe (GCS score of 3 to 8), moderate (GCS score of 9 to 13), and mild (GCS score of 14 or 15) TBI. Mild TBI makes up a majority of head injuries in the U.S. (approximately 80%).1 Moderate TBI accounts for approximately 10% of head injuries. Mortality rates for patients with isolated moderate TBI is <20%, but long-term disability is as high as 50%. Overall, 40% of patients with moderate TBI have an abnormal finding on CT scan and 8% require neurosurgical intervention.2 In severe TBI mortality approaches 40%, with most deaths occurring within the first 48 hours. Fewer than 10% of patients with severe TBI make even a moderate recovery.

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Figure 254-1.
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Each of these CT images shows a distinct trauma-induced pathophysiologic abnormality, yet all patients had a Glasgow Coma Scale score of 4. A. Epidural hematoma. B. Contusion/hematoma. C. Diffuse axonal injury. D. Subdural hematoma. E.Subarachnoid hemorrhage with intraventricular hemorrhage. F. Diffuse edema. (Courtesy of Alisa Gean, MD, University of California, San Francisco.

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Every 15 seconds, a U.S. citizen sustains a significant TBI. Between 1.2 and 2 million Americans sustain a TBI each year.1 In the U.S. alone, it is estimated that TBI is responsible for 50,000 deaths and 235,000 hospitalizations each year. Over 80,000 Americans are disabled annually due to TBI, approximately 17,000 of whom require specialized care for life. Another 37,000 patients experience moderate disabilities.2 Among children aged 0 to 14 years sustaining TBI, it is estimated that 2685 die and 37,000 are hospitalized annually. The aggregate toll of TBI is enormous (Figure 254-1.1). The Centers for Disease Control and Prevention estimates that 5.3 million Americans are living with some degree of disability from a TBI.1

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Figure 254-1.1.
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Average annual traumatic brain injury–related ED visits, hospitalizations, and deaths by external cause in the U.S., 1995 to 2001. (January 2006 update from the National ...

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