conflicts in Afghanistan and Iraq, however, TBI appears to account for about 22% of casualties. 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 TBI. Of those injuries, 56% were moderate or severe, and 44% were mild. In many people who sustain mild TBI, the effects might not be immediately evident and might not be evident with conventional neuroimaging. That clearly presents a problem for VA with regard to preparation for the return of veterans from OEF and OIF with TBI that might not be apparent.
Throughout OEF and OIF, explosive devices have become more powerful, their detonation systems more creative, and their additives more devastating. According to the Department of Defense (DoD) Personnel and Procurement Statistics, 75% of all US military casualties in OEF and OIF are caused by explosive weaponry. As of January 2008, DOD reported that over 5,500 soldiers had suffered TBIs. As a continuing threat to our troops, blast injury, especially blast-induced neurotrauma (BINT), has been called the signature wound of the war in Iraq. In both civilian and military environments, exposure to a blast might cause instant death, injuries with immediate manifestation of symptoms, or injuries with delayed manifestation. BINT is a complex type of TBI that features closed (blunt) head injury that may be accompanied by polytrauma. The pathobiology of BINT parallels that seen in TBI, including secondary injury cascades that result in vasogenic and cytotoxic edema, emerging hemorrhagic lesions, metabolic disturbances, compromise of neural and glial structures that leads to cell death, and diffuse axonal injury in cases of sudden brain acceleration and deceleration.
As of June 30, 2008, there had been about 1.64 million US deployments as part of OEF and OIF and 4,128 US troop fatalities. The ratio of wounded troops to troop fatalities, 7.37:1, is higher than that in previous military conflicts, probably because of the widespread use of body armor, improved battlefield medical response, and advances in aeromedical evacuation. Despite those improvements, military personnel continue to be critically wounded, and TBI continues to be a source of concern. Furthermore, there is an outdated dogma that neurologic impairments caused by primary blasts are rare because the skull provides excellent protection for the brain, that is, that brain injury is a consequence solely of air emboli in cerebral blood vessels. Despite recent clinical findings, experimental findings, and experience in contemporary military operations that suggest that substantial short-term and long-term neurologic deficits can be caused by blast exposure without a direct blow to the head, the old belief prevails in the professional literature and in civilian clinical practice. Indeed, information on blast injuries consists mainly of the consequences of secondary and tertiary blast mechanisms. Although BINT is one cause of in-theater injuries, it is often underdiagnosed. Its complex clinical syndrome is caused by the combination of all blast effects. It is noteworthy that blast injuries are usually manifested in a form of polytrauma, that is, injury involving multiple organs or organ systems.
The charge to this IOM committee was to examine the strength of the evidence of an association between TBI and long-term health effects. The committee also was to consider the severity of TBI (that is, mild, moderate, and severe) and possible long-term consequences.