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.
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.
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
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 ...