Normal myelination: a practical pictorial review.

MRI is currently the best imaging modality to assess myelin maturation in the human brain. Myelin is the insulator for nerves and is present in both the peripheral nervous system and the central nervous system (CNS). In the CNS, it is a modified extension of the oligodendrocyte cell and is made up of multiple sheaths of protein-lipid-protein-lipid-protein. Standard T1-weighted and T2-weighted sequences can be performed on any MR imaging platform and with knowledge of normal age-related myelin maturation, myelin delay can be detected. Myelination progresses in a constant predetermined pattern from bottom to top, central to peripheral and back to front.