Myelination in Children with Partial Deletions of Chromosome 18q

We compared myelin levels in white matter (WM) in typically developing children with those of children with partial deletions of chromosome 18q (18q-). 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. In children with 18q-, the model predicted later onset of myelination (P