The legislation did not preclude an IOM recommendation of or a Department of Veterans Affairs (VA) request for additional studies, particularly if a subject of concern arises. Consequently, a VA request that IOM consider whether there is an increased risk of amyotrophic lateral sclerosis in all veteran populations resulted in Amyotrophic Lateral Sclerosis in Veterans (IOM, 2006a), a request for an examination of all health effects in veterans deployed to the Persian Gulf irrespective of specific exposures resulted in Gulf War and Health, Volume 4: Health Effects of Serving in the Gulf War (IOM, 2006b), and a request for a review of long-term health effects that might be associated with deployment-related stress resulted in Gulf War and Health, Volume 6: Health Effects of Deployment-Related Stress (IOM, 2007). The present report is in response to a VA request regarding whether traumatic brain injury has long-term health effects.
Damage to the brain after trauma (for example, a blow or jolt to the head, a penetrating head injury, or exposure to an external energy source) is referred to as traumatic brain injury (TBI). A TBI may be open (penetrating) or closed and is categorized as mild, moderate, or severe, depending on the clinical presentation (Gennarelli and Graham, 2005). The terms mild, moderate, and severe TBI are defined and discussed in Chapters 2 and 3. A brain injury that results from something passing through the skull, such as a bullet discharged from a gun or fragments from a missile, would be referred to as a penetrating or open head injury. A brain injury that results from something hitting the head or the head hitting something forcefully, such as the dashboard of a car, is referred to as a nonpenetrating or closed head injury. According to the Centers for Disease Control and Prevention, a mild TBI is manifest as a brief change in mental status or unconsciousness, whereas a severe TBI results in an extended period of unconsciousness or amnesia (NCIPC, 2008). According to the World Health Organization Collaborating Task Force on Mild Traumatic Brain Injury, a mild TBI also might be referred to as a concussion, a minor brain injury, a mild head injury, or a minor head injury (von Holst and Cassidy, 2004). Furthermore, von Holst and Cassidy (2004) note that the term concussion is often used to indicate a mild or moderate brain injury, refers to a disturbance in neurologic function caused by “the mechanical force of rapid acceleration and deceleration,” and can cover varied symptoms and severity (see Chapter 2).
Assessment of injury severity is important in the clinical diagnosis and management of patients with TBI. The Glasgow Coma Scale has been the gold standard of neurologic assessment of trauma patients since its development by Teasdale and Jennett in 1974. Other TBI severity-classification systems grade single indicators, such as loss of consciousness and duration of posttraumatic amnesia.
During peacetime, over 7,000 Americans with a TBI diagnosis are admitted to military and veterans hospitals each year. During the Vietnam War, 12–14% of all combat casualties had a TBI, and another 2–4% had a TBI and a lethal wound to the chest or abdomen (Okie, 2005). In the recent conflicts in Afghanistan and Iraq, however, TBI appears to account for a larger percentage of casualties, about 22%. Furthermore, all patients admitted to Walter Reed Army Medical Center in the period January 2003–February 2005 who had been exposed to blasts were routinely evaluated for brain injury, and 59% of them were found to have a TBI. Of those injuries, 56% were moderate or severe, and 44% were mild (Okie, 2005). However, for many