Normal 31-week fetus.
An axial T2-weighted fetal MR image shows the normal lissencephalic character of the developing fetal brain.
A transverse head ultrasound image of a newborn 25-week-gestation infant shows a smooth brain surface that lacks gyral development. The sylvian fissures are shallow. This is a normal appearance for this stage of development.
3. Normal brain development
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.
4. Normal brain myelination
Normal brain myelination.
T2-weighted images in children of different ages. A. Six days. Beginning myelination in the posterior limbs of the internal capsules (arrow) is hypointense. The adjacent thalamic nuclei are also hypointense. B. Two months. There is additional myelination of the posterior aspects of the posterior limbs. The basal ganglia and thalami are hypointense relative to the unmyelinated cerebral white matter. C. Seven months. The entire posterior limbs are myelinated. There is faint hypointensity in the anterior limbs. D. Twelve months. There is myelination of the anterior and posterior limbs of the internal capsules (arrows) and the genu and splenium of the corpus callosum. Hyperintensity of the cerebral white matter is less pronounced.
5. Terminal zone white matter
Terminal zone white matter.
There is mild bilateral peritrigonal white matter hyperintensity (arrows) on this T2-weighted image of a normal 4-year-old child.
6. Cavum septum pellucidum
Cavum septum pellucidum.
The cavum is between the frontal horns on this coronal sonographic image of a 1-day-old infant.
7. Cavum septum pellucidum et vergae
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