Age‐related topographic map of magnetic resonance diffusion metrics in neonatal brains

Abstract

Accelerated maturation of brain parenchyma close to term‐equivalent age leads to rapid changes in diffusion‐weighted imaging (DWI) and diffusion tensor imaging (DTI) metrics of neonatal brains, which can complicate the evaluation and interpretation of these scans. In this study, we characterized the topography of age‐related evolution of diffusion metrics in neonatal brains. We included 565 neonates who had MRI between 0 and 3 months of age, with no structural or signal abnormality—including 162 who had DTI scans. We analyzed the age‐related changes of apparent diffusion coefficient (ADC) values throughout brain and DTI metrics (fractional anisotropy [FA] and mean diffusivity [MD]) along white matter (WM) tracts. Rate of change in ADC, FA, and MD values across 5 mm cubic voxels was calculated. There was significant reduction of ADC and MD values and increase of FA with increasing gestational age (GA) throughout neonates' brain, with the highest temporal rates in subcortical WM, corticospinal tract, cerebellar WM, and vermis. GA at birth had significant effect on ADC values in convexity cortex and corpus callosum as well as FA/MD values in corpus callosum, after correcting for GA at scan. We developed online interactive atlases depicting age‐specific normative values of ADC (ages 34–46 weeks), and FA/MD (35–41 weeks). Our results show a rapid decrease in diffusivity metrics of cerebral/cerebellar WM and vermis in the first few weeks of neonatal age, likely attributable to myelination. In addition, prematurity and low GA at birth may result in lasting delay in corpus callosum myelination and cerebral cortex cellularity.

Impact of postnatal weight gain on brain white matter maturation in very preterm infants

“…These Z‐scores were used instead of raw weight values for all further analyses. In a prior study, we analyzed the DTI scans of a larger cohort of 162 subjects 15 . The current study includes subjects born before 32 weeks gestational from our prior study and includes additional subjects who were outside of the age criteria of the prior study.…”

“…We used the tract‐based spatial statistics (TBSS) toolbox in FSL for voxel‐wise statistical analysis of FA, MD, RD, and AD values along WM tracts 15 . Briefly, each FA map was linearly coregistered to all other FA maps to identify the most representative FA map of the cohort.…”

“…Figure 1 displays the coregistered John's Hopkins University WM atlas overlayed on the pediatric brain template. The means of nonzero FA, MD, RD, and AD values in each of the 48 specific WM tracts were calculated using FSL for each infant 15 . Multiple linear regressions were then applied to determine the association of birth weight Z‐scores with DTI metrics in each WM tract while controlling for gestational age at birth and time between birth and scan as covariates.…”

“…Prior studies have utilized DTI scans obtained in the early postnatal period to characterize WM microstructural development in neonates of varying gestational age 14 . Such works have also identified specific WM regions that experience a microstructural delay in neonates born at lower gestational age, suggesting that DTI can serve as a marker for neurodevelopment for VPIs 15 . Furthermore, as clinical neurological examination and prognostication of long‐term neurodevelopmental outcome using early clinical evaluations in neonates are challenging, neuroimaging performed in the early postnatal period can fill these gaps by providing insight into early brain maturation 16,17 .…”

Alteration of the Oligodendrocyte Lineage Varies According to the Systemic Inflammatory Stimulus in Animal Models That Mimic the Encephalopathy of Prematurity

“…Myelin is visible in the human brain from 30 weeks of gestation and increases thereafter ( Hüppi et al, 1998 ; Mukherjee et al, 2001 ; Bobba et al, 2022 ). However, oligodendrocytes (OLs) appear earlier in the developing brain ( van Tilborg et al, 2018 ).…”