Structural MRI of pediatric brain development: what have we learned and where are we going?

Abstract

Magnetic resonance imaging (MRI) allows unprecedented access to the anatomy and physiology of the developing brain without the use of ionizing radiation. Over the past two decades, thousands of brain MRI scans from healthy youth and those with neuropsychiatric illness have been acquired and analyzed with respect to diagnosis, sex, genetics, and/or psychological variables such as IQ. Initial reports comparing size differences of various brain components averaged across large age spans have given rise to longitudinal studies examining trajectories of development over time and evaluations of neural circuitry as opposed to structures in isolation. Although MRI is still not of routine diagnostic utility for evaluation of pediatric neuropsychiatric disorders, patterns of typical versus atypical development have emerged that may elucidate pathologic mechanisms and suggest targets for intervention. In this review we summarize general contributions of structural MRI to our understanding of neurodevelopment in health and illness.

Figure 1. Developmental Trajectories of Brain Morphometry: Ages 6–20 Years

Mean volume by age in years for males (n = 475 scans) and females (n = 354 scans). Middle lines in each set of three lines represent mean values, and upper and lower lines represent upper and lower 95% confidence intervals. All curves differed significantly in height and shape with the exception of lateral ventricles, in which only height was different, and midsagittal area of the corpus callosum, in which neither height nor shape was different. (A) Total brain volume, (B) gray matter volume, (C) white matter volume, (D) lateral ventricle volume, (E) midsagittal area of the corpus callosum, and (F) caudate volume. Reprinted from Lenroot et al. 2007).

Figure 2. Regional Maturation of Cortical Thickness: Ages 4–21 Years

Right lateral and top views of the dynamic sequence of GM maturation over the cortical surface. The side bar shows a color representation in units of GM volume. Reprinted from Gogtay et al. (2004a).

Figure 3. Developmental Delay of Cortical Thickness in ADHD

Regions where the ADHD group had delayed cortical maturation, as indicated by an older age of attaining peak cortical thickness. Reprinted from Shaw et al. (2006b).