Normal brain development.
Midline T1-weighted MR images of 4 infants at different ages. A. Six days. The corpus callosum is thin and unmyelinated. The early stage of myelination in the cord and brainstem (except the ventral pons) results in subtle hyperintensity. Note hyperintensity of both the anterior and posterior lobes of the pituitary. B. Three months. There is increased myelination of the ventral pons, cerebellar vermis, and dorsal aspect of the corpus callosum. C. Eight months. The brainstem and vermis now have an adult pattern. The corpus callosum is myelinated but is still somewhat thin. D. Eighteen months. The corpus callosum has mature morphology and myelination.