title: Myelination in children with partial deletions of chromosome 18q.
abstract: OBJECTIVE
  We compared myelin levels in white matter (WM) in typically developing children with those of children with partial deletions of chromosome 18q (18q-).
  
  
  METHODS
  Conventional spin-echo MR imaging at 1.9T was used to acquire T1-, T2-, and proton density-weighted images of the brain. From these images, a three-pool model was used to estimate the fraction of water in myelin, myelinated axon, and mixed water compartments (or pools) in six WM regions. A model curve was fit to the pool fractions to model the trend of myelin development by age in each region. Water-pool fractions in children with 18q- aged 5 months to 13 years were compared with those of age-matched, typically developing children.
  
  
  RESULTS
  In children with 18q-, the model predicted later onset of myelination (P <.02), lower myelination rates (P <.001), and smaller equilibrium myelin pool fractions (P <.001). Significant differences were seen between the two groups for all three water pool fractions (P <.001). The mixed pool fraction was larger in children with 18q-. Although the myelin pool fraction was significantly smaller, the myelinated axon pool fraction was only slightly smaller, leading to a significantly smaller estimate of myelin per myelinated axon in children with 18q- (P <.001).
  
  
  CONCLUSIONS
  Myelination modeling in 18q- children indicated delayed onset, a lower rate of myelination, and equilibrium myelin levels less than 50% those of age-matched, typically developing children.
authors.affiliation: Research Imaging Center, University of Texas Health Science Center at San Antonio, TX 78284, USA.
authors.forename: Jack L
authors.initials: JL
authors.lastname: Lancaster
authors.forename: Jannine D
authors.initials: JD
authors.lastname: Cody
authors.forename: Trevor
authors.initials: T
authors.lastname: Andrews
authors.forename: L Jean
authors.initials: LJ
authors.lastname: Hardies
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Hale
authors.forename: Peter T
authors.initials: PT
authors.lastname: Fox
mesh_terms: D001369:Axons / Q000473:pathology; D001921:Brain / Q000473:pathology*; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D002887:Chromosomes, Human, Pair 18; D003711:Demyelinating Diseases / Q000175:diagnosis* / Q000235:genetics*; D005260:Female; D017353:Gene Deletion; D006801:Humans; D007223:Infant; D008279:Magnetic Resonance Imaging; D008297:Male; D008959:Models, Neurological; D009186:Myelin Sheath / Q000473:pathology*