Epidemiology of moderate-to-severe penetrating versus closed traumatic brain injury in the Iraq and Afghanistan wars.

BACKGROUND US combat operations in Iraq and Afghanistan have resulted in a greater proportion of service members with head and neck wounds caused by explosions compared with that of previous wars. Although penetrating traumatic brain injury (TBI) is frequently associated with these wounds, the epidemiology of penetrating TBI from these conflicts has not been well described. METHODS The Joint Theater Trauma Registry was queried for January 2003 through December 2010 to identify all patients with moderate-to-severe brain injury with a maximum Abbreviated Injury Scale (AIS) score of the head of 3 or greater and a diagnosis of penetrating or closed TBI in accordance with the Department of Defense Traumatic Brain Injury Surveillance definition. The epidemiology of these injuries was examined, including demographics, TBI severity, overall injury severity, and surgical interventions provided. RESULTS A total of 1,255 TBI patients (774 penetrating, 481 closed) meeting criteria were identified. Penetrating brain injuries were more severe, more likely to be battle related, and less likely to be isolated injuries than a group of moderate-to-severe closed TBIs within the same range of anatomic injury severity. During the 5-year period of the Iraq war with the largest numbers of TBIs (2004-2008), the numbers of penetrating TBIs exceeded closed TBIs by a ratio of 2:1. During the 3-year period of the Afghanistan war with the greatest numbers of TBIs (2008-2010), the ratio of penetrating to closed TBIs was substantially lower, approximately 1.3:1. CONCLUSION This study represents the first comprehensive report on the epidemiology of moderate-to-severe penetrating and closed TBIs resulting from the wars in Iraq and Afghanistan using Joint Theater Trauma Registry data. With the maturing theater of conflicts, penetrating TBIs were substantially less predominant compared with closed TBIs. While this finding may reflect changes in the use of protective measures and tactics or improvements in diagnosis of closed TBIs, additional research is needed to identify the reason for this shift and the subsequent effect on outcome after combat-related TBIs. LEVEL OF EVIDENCE Epidemiologic study, level III.