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.

Post-viral effects of COVID-19 in the olfactory system and their implications.

BACKGROUND: The mechanisms by which any upper respiratory virus, including SARS-CoV-2, impairs chemosensory function are not known. COVID-19 is frequently associated with olfactory dysfunction after viral infection, which provides a research opportunity to evaluate the natural course of this neurological finding. Clinical trials and prospective and histological studies of new-onset post-viral olfactory dysfunction have been limited by small sample sizes and a paucity of advanced neuroimaging data and neuropathological samples. Although data from neuropathological specimens are now available, neuroimaging of the olfactory system during the acute phase of infection is still rare due to infection control concerns and critical illness and represents a substantial gap in knowledge. RECENT DEVELOPMENTS: The active replication of SARS-CoV-2 within the brain parenchyma (ie, in neurons and glia) has not been proven. Nevertheless, post-viral olfactory dysfunction can be viewed as a focal neurological deficit in patients with COVID-19. Evidence is also sparse for a direct causal relation between SARS-CoV-2 infection and abnormal brain findings at autopsy, and for trans-synaptic spread of the virus from the olfactory epithelium to the olfactory bulb. Taken together, clinical, radiological, histological, ultrastructural, and molecular data implicate inflammation, with or without infection, in either the olfactory epithelium, the olfactory bulb, or both. This inflammation leads to persistent olfactory deficits in a subset of people who have recovered from COVID-19. Neuroimaging has revealed localised inflammation in intracranial olfactory structures. To date, histopathological, ultrastructural, and molecular evidence does not suggest that SARS-CoV-2 is an obligate neuropathogen. WHERE NEXT?: The prevalence of CNS and olfactory bulb pathosis in patients with COVID-19 is not known. We postulate that, in people who have recovered from COVID-19, a chronic, recrudescent, or permanent olfactory deficit could be prognostic for an increased likelihood of neurological sequelae or neurodegenerative disorders in the long term. An inflammatory stimulus from the nasal olfactory epithelium to the olfactory bulbs and connected brain regions might accelerate pathological processes and symptomatic progression of neurodegenerative disease. Persistent olfactory impairment with or without perceptual distortions (ie, parosmias or phantosmias) after SARS-CoV-2 infection could, therefore, serve as a marker to identify people with an increased long-term risk of neurological disease.

Analysis of battlefield head and neck injuries in Iraq and Afghanistan.

OBJECTIVE: At the time of this study, the 1st place that an injured or ill American soldier in Iraq or Afghanistan would have been evaluated by an ENT-head and neck surgeon was at a tertiary care medical center as a result of air evacuation out of theater: Landstuhl Regional Medical Center (LRMC), Ramstein, Germany. By examining the ENT-related diagnoses of all air evacuations from downrange, we were able to match the patients classified as having battle injuries to determine the percentage with head and neck trauma. STUDY DESIGN: A prospective review of 11,287 soldiers air-evacuated from Afghanistan and Iraq, representing the 1st year of combat operations. A new, computerized patient-tracking system was created by our team to merge several disparate databases to generate and compile our data. RESULTS: The ENT-head and neck surgery department evaluated and primarily managed 8.7% of all patients evacuated out of theater by air to Germany. Other medical and surgical services managed 7.3% of all patients evacuated out of theater with overlapping ENT diagnoses. The number of potential ENT patients increased to 16% when one looked at all head and neck pathology instances seen by all medical and surgical departments hospitalwide. Of all patients air-evacuated and classified as having battle injuries, 21% presented with at least 1 head and neck trauma code. CONCLUSIONS: This is the 1st paper focusing on the role of the ENT-head and neck surgeon in treating a combat population and also the patterns of illness and head and neck injuries in a deployed force in our modern military. Improved soldier body armor has resulted in distinctly new patterns of combat injuries. Unprotected areas of the body account for the majority of injuries. SIGNIFICANCE: These findings should be used to improve the planning and delivery of combat medical care.

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%).