Maturation of the brainstem and cerebellar white matter tracts from the neonatal period to adolescence: a diffusion tensor imaging study

Aims: Diffusion tensor imaging (DTI) allows to study the normal development of white matter tracts. Several studies focused on the supratentorial white matter tracts. Almost no data are available about the temporal changes of DTI scalars for the infratentorial white matter tracts during the progressing myelination. We evaluated the quantitative changes of fractional anisotropy (FA) and mean (MD), axial (AD), and radial (RD) diffusivity within the brainstem and cerebellar white matter tracts from the neonatal period to adolescence. Methods: We selected 96 subjects (47 females, 49 males, age 3 days to 17.9 years) with normal brain anatomy and absence of neurological disorders. Single shot spin-echo, echo-planar axial DTI sequences were acquired on a 1.5T MR scanner. Balanced pairs of diffusion gradients were applied along 20 orthogonal directions. Atlas-based analysis with parcellation of the brain in 130 regions was performed using MRI Studio software. The following infratentorial white matter tracts were evaluated: corticospinal tract, medial lemniscus, and superior, middle, and inferior cerebellar peduncles. Results: For all white matter tracts, an increase of FA and decrease of MD, RD, and less pronounced AD values was seen over time. For all white matter tracts, changes in DTI parameters were higher for the youngest subjects (younger than 12 months of age). Additionally, changes in DTI parameters, particularly MD, RD, and AD, differed depending on the studied white matter tracts and were higher for the corticospinal tracts and middle cerebellar peduncles compared with medial lemnisci and superior and inferior cerebellar peduncles. Conclusion: The changes in DTI parameters correlate well with the normal myelination and developmental processes. The most pronounced changes were seen in white matter tracts that myelinate later. We report on normative values for pediatric DTI parameters of the infratentorial white matter tracts using atlas-based analysis.