Epidemiology and Outcomes of Battlefield-Related Penetrating and Closed Traumatic Brain Injuries Compared to Non-Head Injuries: A Retrospective Cohort Study

Introduction Traumatic brain injuries (TBIs) are associated with substantial morbidity and mortality. We examined characteristics and outcomes among military personnel with battlefield-related penetrating TBI (pTBI) compared to closed TBI (cTBI) and non-head injuries (without cranial injuries). Materials and Methods Military personnel admitted to participating U.S. military hospitals (2009-2014) were classified based on injury patterns: pTBI, cTBI (head Abbreviated Injury Scale [AIS] ≥3), and non-head (≥1 non-head injury AIS ≥3). Propensity score and inverse probability of treatment weighting (IPTW) were used to assess associations with mortality, hospital stay, and infection burden. Results The study population included 106 pTBI patients, 259 cTBI patients, and 715 patients with non-head injuries. Patients with pTBIs were more severely injured with differing injury mechanisms compared to the other 2 groups. Patients with pTBIs had more critical care requirements versus both cTBI and non-head injury patients (P < .05) and longer hospitalization (median 27 days vs. 22; P = .041) compared to cTBI patients. More central nervous system (CNS) infections were diagnosed among patients with pTBIs (11.3%) versus cTBIs (1.2%) and non-head injuries (0.7%; P < .001). Although the overall proportion of patients who developed non-CNS infections was not significantly different between the TBI groups, there was a higher proportion among pTBI versus non-head injury patients (53.8% vs. 40.8%; P = .012). Patients with pTBIs also had less skin and soft-tissue infections and more pneumonia compared to non-head injury patients (P < .05). There was no significant difference in the proportion of mortality between the pTBI and cTBI patients (7.6% vs. 3.1%); however, it was higher compared to patients with non-head injuries (1.0%; P < .001). Sustaining any TBI (penetrating or closed) was associated with greater risk of mortality compared to non-head injuries (risk ratio: 3.71; 95% CI, 1.83-7.55). Conclusions Patients with pTBIs are critically injured with substantial critical care requirements and morbidity. Between patients with pTBIs and cTBIs, there was not a significant difference in non-CNS infection burden or mortality, but pTBI patients did have longer hospitalization. When compared to severely injured military personnel with non-head injuries using propensity scores and IPTW analysis, sustaining a TBI (penetrating or closed) was not associated with having more non-CNS infections or a longer hospital stay. This may be a result of the high injury severity (median of 26) and relative occurrence of polytrauma in the total population. Patients with TBIs (penetrating or closed) did have a greater risk of mortality compared to patients with non-head injuries.