What are the expected MRI findings of brain myelination in a typically developing child by 18 months of age?

By 18 months, brain MRI should show an adult-like pattern of myelination, with the exception of terminal myelination zones in the periatrial region and adjacent to the frontal horns. Key diagnostic features include high T1 and low T2 signal intensity in myelinated areas. Clinically, recognizing these patterns helps differentiate normal development from pathological delays. A common pitfall is mistaking delayed myelination for leukodystrophy; correlating clinical history and progression is essential.