Sequence of central nervous system myelination in human infancy. II. Patterns of myelination in autopsied infants.

The timing and synchronization of postnatal myelination in the human central nervous system (CNS) are complex. We found eight time-related patterns of CNS myelination during the first two postnatal years in autopsied infants. The intensity of myelination was graded in 162 infants with diverse diseases on an ordinal scale of degrees 0-4. The Ayer method for maximum likelihood estimates for censored data was utilized to generate curves of the temporal changes in the percent of infants with degrees 0 through 4 of myelin in 62 white matter sites. These sites fall into eight subgroups determined by the presence or absence of microscopic myelin (degree 1) at birth and the median age at which mature myelin (degree 3) is reached. There is variability in the timing of myelination within and across axonal systems, and early onset of myelination is not always followed by early myelin maturation. We reexamined general rules governing the timing of myelination proposed by previous investigators, and found that those rules are neither complete nor inviolate, and that there is a complex interplay among them. This study specifies distinct periods of maturation in which myelinating pathways are potentially vulnerable to insult during the first two postnatal years.

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.

Nonvasculitic, steroid-responsive mononeuritis multiplex.

We report two patients with mononeuritis multiplex, both of whom had focal inflammation of the perineurium and endoneurium on sural nerve biopsy without necrosis of blood vessel walls, histologic evidence of lymphoid malignancy, or mycobacterial infection. The predominant early sensory symptoms were asymmetric pain and paresthesias; subsequently, muscle weakness developed. Electrophysiologic studies showed an asymmetric sensorimotor axon loss radiculoneuropathy with denervation of limb and paraspinal muscles. Spinal fluid protein was elevated in one patient. There was no cause or underlying systemic disease. Marked improvement occurred with steroid therapy.