Sequence of Central Nervous System Myelination in Human Infancy. I. An Autopsy Study of Myelination

This study establishes the sequence of myelination in a population of autopsied infants from birth through the second postnatal year. Myelination was assessed in 62 precisely defined central nervous system (CNS) sites of 162 infants with diverse diseases who were autopsied from 1972 to 1984 at Children's Hospital, Boston. The degree of myelination was graded on an ordinal scale of 0-4 using the inferior cerebellar peduncle as an internal standard. This grading system is a modification of that used for fetal myelination in the National Collaborative Perinatal Project (NCPP). The data are summarized by, median degree of myelination for each age group and site; and Ayer estimates for the age at which at least 10, 50, and 90% of infants reach a particular myelin degree in each site. "Marker" sites in the cerebrum are provided for the pathologist to compare myelination between an individual infant brain and the brains from our autopsy population. These data should be useful in identifying diverse peri- and postnatal conditions affecting myelination in human infancy. They also provide guidelines for the assessment of CNS myelination by sophisticated imaging techniques in living infants.