Two-year Mortality and Functional Outcomes in Combat-related Penetrating Brain Injury: Battlefield Through Rehabilitation

M. Benjamin Larkin, MD, PharmD; Erin K. M. Graves, MD, MA; Jason H. Boulter, MD; Nicholas S. Szuflita, MD, MPH; R. Michael Meyer, MD; Michael E. Porambo, MD; John J. Delaney, MD; Randy S. Bell, MD

Disclosures

Neurosurg Focus. 2019;45(6):e4 

In This Article

Abstract and Introduction

Abstract

Objective: There are limited data concerning the long-term functional outcomes of patients with penetrating brain injury. Reports from civilian cohorts are small because of the high reported mortality rates (as high as 90%). Data from military populations suggest a better prognosis for penetrating brain injury, but previous reports are hampered by analyses that exclude the point of injury. The purpose of this study was to provide a description of the long-term functional outcomes of those who sustain a combat-related penetrating brain injury (from the initial point of injury to 24 months afterward).

Methods: This study is a retrospective review of cases of penetrating brain injury in patients who presented to the Role 3 Multinational Medical Unit at Kandahar Airfield, Afghanistan, from January 2010 to March 2013. The primary outcome of interest was Glasgow Outcome Scale (GOS) score at 6, 12, and 24 months from date of injury.

Results: A total of 908 cases required neurosurgical consultation during the study period, and 80 of these cases involved US service members with penetrating brain injury. The mean admission Glasgow Coma Scale (GCS) score was 8.5 (SD 5.56), and the mean admission Injury Severity Score (ISS) was 26.6 (SD 10.2). The GOS score for the cohort trended toward improvement at each time point (3.6 at 6 months, 3.96 at 24 months, p > 0.05). In subgroup analysis, admission GCS score ≤ 5, gunshot wound as the injury mechanism, admission ISS ≥ 26, and brain herniation on admission CT head were all associated with worse GOS scores at all time points. Excluding those who died, functional improvement occurred regardless of admission GCS score (p < 0.05). The overall mortality rate for the cohort was 21%.

Conclusions: Good functional outcomes were achieved in this population of severe penetrating brain injury in those who survived their initial resuscitation. The mortality rate was lower than observed in civilian cohorts.

Introduction

SEVERE closed and penetrating brain injuries (PBIs) remain considerable clinical and research challenges, and there is a relative paucity of evidence to guide management practices. This is due largely to the fact that the majority of PBI patients seen at civilian trauma centers in the US are victims of gunshot wounds to the head (GSWH) and their prognosis is poor,[2,16,24,27] with overall mortality cited to be as high as 91%.[1] The majority of these deaths occur at the point of injury or shortly thereafter. Aarabi et al. reported in 2014 that 76% of 786 patients died at the point of injury, which is consistent with the 71% reported by Kaufman et al. in 1986 and the 73% reported by Siccardi et al. in 1991.[1,17,34]

For patients who sustain PBI and do survive their injuries, little is known about their potential for a functional recovery. In a review of 4 previous studies concerning civilian GSWH,[2,16,24,27] a total of 349 patients were re-stratified on the basis of their admission Glasgow Coma Scale (GCS) and long-term Glasgow Outcome Scale (GOS) scores (with GOS scores ≥ 4 indicating a good functional outcome). This review found that 66% had an admission GCS score of 3–5 and 93% of patients in this group died, with only 2 patients (0.9%) ever achieving functional independence, defined by a GOS ≥ 4.[5] In the remaining one-third of patients with an admission GCS score ≥ 6, 60% eventually achieved functional independence.[5] In all, 21% of patients who presented to the emergency department after damage control resuscitation ever achieved functional independence.[5]

In contrast, a 2012 study by Weisbrod et al. of 137 military PBI patients managed at the Walter Reed National Military Medical Center (WRNMMC) reported 5.8% mortality and 68% achievement of functional independence (mean GOS 4).[35] Notably, 32% of those with an admission GCS score of 3–5 ultimately had a GOS score ≥ 4. This contrasts markedly with the < 1% of civilian patients with similar admission GCS scores.[5] While a superficial analysis might conclude that this represents a significant difference in survivability between military and civilian cohorts, this conclusion cannot be drawn based on available data due to immortal time bias. The study by Weisbrod et al., like many before it, was unable to account for those who died prior to arrival at hospitals within the US and therefore may overestimate the survivability of PBI in that cohort.[3,4,13,28,35]

With this in mind, our purpose in this paper was to characterize the long-term outcomes of those who sustain combat-related PBI by analyzing a cohort of patients from point of injury forward. The following is therefore a retrospective analysis of a cohort of active-duty US military personnel who sustained a PBI in combat and survived to be evaluated by a deployed neurosurgeon and for whom GOS scores could be calculated at 6, 12, and 24 months after injury.

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