title: Abnormal myelin and axonal integrity in recently diagnosed patients with obstructive sleep apnea.
abstract: OBJECTIVE
  Patients with obstructive sleep apnea (OSA) show significant white matter injury; whether that injury represents myelin or axonal damage is unclear. The objective was to examine myelin and axonal changes in patients with newly diagnosed OSA over control subjects.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  University-based medical center.
  
  
  METHODS
  Twenty-three newly-diagnosed, treatment-naïve OSA and 23 age- and sex-matched control subjects.
  
  
  METHODS
  None.
  
  
  RESULTS
  Radial and axial diffusivity maps, calculated from diffusion tensor imaging data (3.0 Tesla MRI scanner), indicating diffusion perpendicular (myelin status) or parallel (axonal status) to fibers, respectively, were normalized, smoothed, and compared between groups (analysis of covariance; covariate: age). Global brain radial and axial diffusivity values, and global brain volume with myelin and axonal changes were determined, and region-of-interest analyses performed in areas of significant differences between groups based on voxel-based procedures. Global radial and axial diffusivity values were significantly reduced in OSA versus control subjects (radial, P = 0.004; axial, P = 0.019), with radial (myelin) diffusivity reduced more than axial (axonal), and more left-sided reduction for both measures. Localized declines for myelin and axonal measures appeared in the dorsal and ventral medulla, cerebellar cortex and deep nuclei, basal ganglia, hippocampus, amygdala, corpus callosum, insula, cingulate and medial frontal cortices, and other cortical areas (P < 0.005), all regions mediating functions affected in OSA.
  
  
  CONCLUSIONS
  Fiber injury appears in critical medullary respiratory regulatory sites, as well as cognitive and autonomic control areas. Myelin is more affected in newly diagnosed OSA than axons, and primarily on the left side, possibly from the increased myelin sensitivity to hypoxia and asymmetric perfusion.
authors.affiliation: Department of Anesthesiology ; Department of Radiological Sciences ; The Brain Research Institute, University of California at Los Angeles, Los Angeles, CA.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Kumar
authors.affiliation: Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA.
authors.forename: Tiffany T
authors.initials: TT
authors.lastname: Pham
authors.affiliation: UCLA School of Nursing, Los Angeles, CA ; The Brain Research Institute, University of California at Los Angeles, Los Angeles, CA.
authors.forename: Paul M
authors.initials: PM
authors.lastname: Macey
authors.affiliation: UCLA School of Nursing, Los Angeles, CA.
authors.forename: Mary A
authors.initials: MA
authors.lastname: Woo
authors.affiliation: Department of Neurology, David Geffen School of Medicine at UCLA, Los Angeles, CA.
authors.forename: Frisca L
authors.initials: FL
authors.lastname: Yan-Go
authors.affiliation: Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA ; The Brain Research Institute, University of California at Los Angeles, Los Angeles, CA.
authors.forename: Ronald M
authors.initials: RM
authors.lastname: Harper
mesh_terms: D000328:Adult; D000368:Aged; D001369:Axons / Q000473:pathology*; D001921:Brain / Q000473:pathology*; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D056324:Diffusion Tensor Imaging; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009186:Myelin Sheath / Q000473:pathology*; D009413:Nerve Fibers, Myelinated / Q000473:pathology*; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis / Q000473:pathology*
keywords: Acute; brain; diffusion; hypoxia; medulla; respiration; tensor imaging