Olfactory impairment and traumatic brain injury in blast-injured combat troops: a cohort study.

OBJECTIVE: To determine whether a structured and quantitative assessment of differential olfactory performance-recognized between a blast-injured traumatic brain injury (TBI) group and a demographically comparable blast-injured control group-can serve as a reliable antecedent marker for preclinical detection of intracranial neurotrauma. METHODS: We prospectively and consecutively enrolled 231 polytrauma inpatients, acutely injured from explosions during combat operations in either Afghanistan or Iraq and requiring immediate stateside evacuation and sequential admission to our tertiary care medical center over a 2½-year period. This study correlates olfactometric scores with both contemporaneous neuroimaging findings as well as the clinical diagnosis of TBI, tabulates population-specific incidence data, and investigates return of olfactory function. RESULTS: Olfactometric score predicted abnormal neuroimaging significantly better than chance alone (area under the curve = 0.78, 95% confidence interval [CI] 0.70-0.87). Normosmia was present in all troops with mild TBI (i.e., concussion) and all control subjects. Troops with radiographic evidence of frontal lobe injuries were 3 times more likely to have olfactory impairment than troops with injuries to other brain regions (relative risk 3.0, 95% CI 0.98-9.14). Normalization of scores occurred in all anosmic troops available for follow-up testing. CONCLUSION: Quantitative identification olfactometry has limited sensitivity but high specificity as a marker for detecting acute structural neuropathology from trauma. When considering whether to order advanced neuroimaging, a functional disturbance with central olfactory impairment should be regarded as an important tool to inform the decision process. CLASSIFICATION OF EVIDENCE: This study provides Class III evidence that central olfactory dysfunction identifies patients with TBI who have intracranial radiographic abnormalities with a sensitivity of 35% (95% CI 20.6%-51.7%) and specificity of 100% (95% CI 97.7%-100.0%).

Epidemiologic aspects of traumatic brain injury in acute combat casualties at a major military medical center: a cohort study.

OBJECTIVE: From the ongoing military conflicts in Iraq and Afghanistan, an understanding of the neuroepidemiology of traumatic brain injury (TBI) has emerged as requisite for further advancements in neurocombat casualty care. This study reports population-specific incidence data and investigates TBI identification and grading criteria with emphasis on the role of loss of consciousness (LOC) in the diagnostic rubric. METHODS: This is a cohort study of all consecutive troops acutely injured during combat operations-sustaining body-wide injuries sufficient to require immediate stateside evacuation-and admitted sequentially to our medical center during a 2-year period. A prospective exploration of the TBI identification and grading system was performed in a homogeneous population of blast-injured polytrauma inpatients. RESULTS: TBI incidence was 54.3%. Structural neuroimaging abnormalities were identified in 14.0%. Higher Injury Severity Score (ISS) was associated with abnormal neuroimaging, longer length of stay (LOS), and elevated TBI status-primarily based on autobiographical LOC. Mild TBI patients had normal neuroimaging, higher ISS, and comparable LOS to TBI-negative patients. Patients who reported LOC had a lower incidence of abnormal neuroimaging. INTERPRETATION: This study demonstrates that the methodology used to assign the diagnosis of a mild TBI in troops with complex combat-related injuries is crucial to an accurate accounting. The detection of incipient mild TBI, based on an identification system that utilizes LOC as the principal diagnostic criterion to discern among patients with outcomes of interest, misclassifies patients whose LOC may not reflect actual brain injury. Attempts to identify high-risk battlefield casualties within the current point-of-injury mild TBI case definition, which favors high sensitivity, will be at the expense of specificity.

Outcomes of 33 patients from the wars in Iraq and Afghanistan undergoing bilateral or bicompartmental craniectomy.

OBJECT: There are no published long-term data for patients with penetrating head injury treated with bilateral supratentorial craniectomy, or supra- and infratentorial craniectomy. The authors report their experience with 33 patients treated with bilateral or bicompartmental craniectomy from the ongoing conflicts in Iraq and Afghanistan. METHODS: An exploratory analysis of Glasgow Outcome Scale (GOS) scores at 6 months in 33 patients was performed. Follow-up lasting a median of more than 2 years was performed in 30 (91%) of these patients. The association of GOS score with categorical variables was explored using the Wilcoxon rank-sum test or Kruskal-Wallis analysis of variance. The Spearman correlation coefficient was used for ordinal/continuous data. To provide a clinically meaningful format to present GOS scores with categorical variables, patients with GOS scores of 1-3 were categorized as having a poor outcome and those with scores of 4 and 5 as having a good outcome. This analysis does not include the patients who died in theater or in Germany who underwent bilateral decompressive craniectomy because those figures have not been released due to security concerns. RESULTS: All patients were men with a median age of 24 years (range 19-46 years) and a median initial Glasgow Coma Scale (GCS) score of 5 (range 3-14). At 6 months, 9 characteristics were statistically significant: focus of the initial injury, systemic infection, initial GCS score, initial GCS score excluding patients with a GCS score of 3, GCS score on arrival to the US, GCS score on dismissal from the medical center, Injury Severity Score, and patients with cerebrovascular injury. Six factors were significant at long-term follow-up: focus of initial injury, systemic infection, initial GCS score excluding patients with a GCS score of 3, GCS score on arrival to the US, and GCS score on dismissal from the medical center. At long-term follow-up, 7 (23%) of 30 patients had died, 5 (17%) of 30 had a GOS score of 2 or 3, and 18 (60%) of 30 had a GOS score of 4 or 5. CONCLUSIONS: In this selected group of patients who underwent bilateral or bicompartmental craniectomy, 60% are independent at long-term follow-up. Patients with bifrontal injury fared best. Systemic infection and cerebrovascular injury corresponded with a worse outcome.