title: White matter hyperintensities on MRI in high-altitude U-2 pilots.
abstract: OBJECTIVE
  To demonstrate that U-2 pilot occupational exposure to hypobaria leads to increased incidence of white matter hyperintensities (WMH) with a more uniform distribution throughout the brain irrespective of clinical neurologic decompression sickness history.
  
  
  METHODS
  We evaluated imaging findings in 102 U-2 pilots and 91 controls matched for age, health, and education levels. Three-dimensional, T2-weighted, high-resolution (1-mm isotropic) imaging data were collected using fluid-attenuated inversion recovery sequence on a 3-tesla MRI scanner. Whole-brain and regional WMH volume and number were compared between groups using a 2-tailed Wilcoxon rank sum test.
  
  
  RESULTS
  U-2 pilots demonstrated an increase in volume (394%; p = 0.004) and number (295%; p < 0.001) of WMH. Analysis of regional distribution demonstrated WMH more uniformly distributed throughout the brain in U-2 pilots compared with mainly frontal distribution in controls.
  
  
  CONCLUSIONS
  Pilots with occupational exposure to hypobaria showed a significant increase in WMH lesion volume and number. Unlike the healthy controls with predominantly WMH in the frontal white matter, WMH in pilots were more uniformly distributed throughout the brain. This is consistent with our hypothesized pattern of damage produced by interaction between microemboli and cerebral tissue, leading to thrombosis, coagulation, inflammation, and/or activation of innate immune response, although further studies will be necessary to clarify the pathologic mechanisms responsible.
authors: U.S. Air Force School of Aerospace Medicine, Aerospace Medicine Consultation Division, Wright-Patterson AFB, OH, USA. smcguire@satx.rr.com
authors: Stephen
authors: S
authors: McGuire
authors: Paul
authors: P
authors: Sherman
authors: Leonardo
authors: L
authors: Profenna
authors: Patrick
authors: P
authors: Grogan
authors: John
authors: J
authors: Sladky
authors: Anthony
authors: A
authors: Brown
authors: Andrew
authors: A
authors: Robinson
authors: Laura
authors: L
authors: Rowland
authors: Elliot
authors: E
authors: Hong
authors: Beenish
authors: B
authors: Patel
authors: David
authors: D
authors: Tate
authors: Elaine S
authors: ES
authors: Kawano
authors: Peter
authors: P
authors: Fox
authors: Peter
authors: P
authors: Kochunov
mesh_terms: D000328:Adult; D000401:Aircraft / Q000706:statistics & numerical data*; D001921:Brain / Q000473:pathology*; D003665:Decompression Sickness / Q000453:epidemiology* / Q000473:pathology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000706:statistics & numerical data*; D008297:Male; D008875:Middle Aged; D008889:Military Personnel / Q000706:statistics & numerical data*; D009413:Nerve Fibers, Myelinated / Q000473:pathology*; D015995:Prevalence; D012307:Risk Factors; D014481:United States / Q000453:epidemiology
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