Myelination of the human vagus nerve from 24 weeks postconceptional age to adolescence

Abstract

Significant changes in respiratory reflexes occur with maturation. The vagus nerve, the pathway for the Hering-Breuer and irritant-receptor reflexes, was studied quantitatively in 33 infants and 5 adolescents. In the infants, total myelinated vagus fibers increased linearly (r = +0.682, p < 0.001) with postconceptional age (PCA), and by 40 weeks after conception, total counts were comparable to those of adolescent group. Counts of total myelinated vagus fibers in 16 term infants (s=41 weeks PCA) were comparable to those in the adolescent group (p < 0.40), whereas 17 preterm infants (=s38 weeks PCA) showed significantly fewer total myelinated vagus fibers than term or adolescent groups (p < O.0G1). Smaller-diameter (=s2 jitm) myelinated vagus fibers depended upon PCA in the preterm group (p < 0.005), but were independent of PCA in the term group (p < 0.5). Preterm infants have a higher percentage of small to total myelinated vagus fibers than term infants (p < 0.1). © 1982 by the American Association of Neuropathologists.