title: Olfactory impairment and traumatic brain injury in blast-injured combat troops: a cohort study.
abstract: 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.
  
  
  CONCLUSIONS
  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.
  
  
  METHODS
  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%).
authors: From Otorhinolaryngology/Head & Neck Surgery (M.S.X.), Neurosurgery (L.P.M.), and Neuroradiology (A.B.S.), Walter Reed National Military Medical Center, Bethesda; Traumatic Brain Injury Surgical Research Program (M.S.X., L.P.M., D.M.L.), Otorhinolaryngology/Head & Neck Surgery (M.S.X.), Neurosurgery (L.P.M.), Neuroradiology (A.B.S.), Preventive Medicine & Biostatistics (C.H.O.), Uniformed Services University (M.S.X., L.P.M., A.B.S., D.M.L.), Bethesda; and Neurological Disorders and Stroke (L.B.), National Institutes of Health, Bethesda, MD. michael.xydakis@usuhs.edu.
authors: Michael S
authors: MS
authors: Xydakis
authors: From Otorhinolaryngology/Head & Neck Surgery (M.S.X.), Neurosurgery (L.P.M.), and Neuroradiology (A.B.S.), Walter Reed National Military Medical Center, Bethesda; Traumatic Brain Injury Surgical Research Program (M.S.X., L.P.M., D.M.L.), Otorhinolaryngology/Head & Neck Surgery (M.S.X.), Neurosurgery (L.P.M.), Neuroradiology (A.B.S.), Preventive Medicine & Biostatistics (C.H.O.), Uniformed Services University (M.S.X., L.P.M., A.B.S., D.M.L.), Bethesda; and Neurological Disorders and Stroke (L.B.), National Institutes of Health, Bethesda, MD.
authors: Lisa P
authors: LP
authors: Mulligan
authors: From Otorhinolaryngology/Head & Neck Surgery (M.S.X.), Neurosurgery (L.P.M.), and Neuroradiology (A.B.S.), Walter Reed National Military Medical Center, Bethesda; Traumatic Brain Injury Surgical Research Program (M.S.X., L.P.M., D.M.L.), Otorhinolaryngology/Head & Neck Surgery (M.S.X.), Neurosurgery (L.P.M.), Neuroradiology (A.B.S.), Preventive Medicine & Biostatistics (C.H.O.), Uniformed Services University (M.S.X., L.P.M., A.B.S., D.M.L.), Bethesda; and Neurological Disorders and Stroke (L.B.), National Institutes of Health, Bethesda, MD.
authors: Alice B
authors: AB
authors: Smith
authors: From Otorhinolaryngology/Head & Neck Surgery (M.S.X.), Neurosurgery (L.P.M.), and Neuroradiology (A.B.S.), Walter Reed National Military Medical Center, Bethesda; Traumatic Brain Injury Surgical Research Program (M.S.X., L.P.M., D.M.L.), Otorhinolaryngology/Head & Neck Surgery (M.S.X.), Neurosurgery (L.P.M.), Neuroradiology (A.B.S.), Preventive Medicine & Biostatistics (C.H.O.), Uniformed Services University (M.S.X., L.P.M., A.B.S., D.M.L.), Bethesda; and Neurological Disorders and Stroke (L.B.), National Institutes of Health, Bethesda, MD.
authors: Cara H
authors: CH
authors: Olsen
authors: From Otorhinolaryngology/Head & Neck Surgery (M.S.X.), Neurosurgery (L.P.M.), and Neuroradiology (A.B.S.), Walter Reed National Military Medical Center, Bethesda; Traumatic Brain Injury Surgical Research Program (M.S.X., L.P.M., D.M.L.), Otorhinolaryngology/Head & Neck Surgery (M.S.X.), Neurosurgery (L.P.M.), Neuroradiology (A.B.S.), Preventive Medicine & Biostatistics (C.H.O.), Uniformed Services University (M.S.X., L.P.M., A.B.S., D.M.L.), Bethesda; and Neurological Disorders and Stroke (L.B.), National Institutes of Health, Bethesda, MD.
authors: Dina M
authors: DM
authors: Lyon
authors: From Otorhinolaryngology/Head & Neck Surgery (M.S.X.), Neurosurgery (L.P.M.), and Neuroradiology (A.B.S.), Walter Reed National Military Medical Center, Bethesda; Traumatic Brain Injury Surgical Research Program (M.S.X., L.P.M., D.M.L.), Otorhinolaryngology/Head & Neck Surgery (M.S.X.), Neurosurgery (L.P.M.), Neuroradiology (A.B.S.), Preventive Medicine & Biostatistics (C.H.O.), Uniformed Services University (M.S.X., L.P.M., A.B.S., D.M.L.), Bethesda; and Neurological Disorders and Stroke (L.B.), National Institutes of Health, Bethesda, MD.
authors: Leonardo
authors: L
authors: Belluscio
mesh_terms: D000328:Adult; D055826:Afghan Campaign 2001-; D015415:Biomarkers; D001753:Blast Injuries / Q000150:complications / Q000175:diagnosis* / Q000453:epidemiology; D001924:Brain Concussion / Q000150:complications / Q000175:diagnosis / Q000453:epidemiology; D001930:Brain Injuries / Q000150:complications / Q000175:diagnosis* / Q000453:epidemiology; D015331:Cohort Studies; D005260:Female; D005625:Frontal Lobe / Q000293:injuries*; D006801:Humans; D054542:Iraq War, 2003-2011; D008297:Male; D008889:Military Personnel / Q000706:statistics & numerical data*; D000857:Olfaction Disorders / Q000175:diagnosis* / Q000453:epidemiology / Q000209:etiology; D064367:Olfactometry / Q000592:standards*; D012680:Sensitivity and Specificity; D014481:United States / Q000453:epidemiology; D055815:Young Adult
chemical_list: D015415:Biomarkers