Myenteric plexus neuropathy in infantile hypertrophic pyloric stenosis

The myenteric plexus and intramuscular nerve bundles in the circular muscle layer of the pylorus from 37 children with infantile hypertrophic pyloric stenosis (IHPS) obtained at pyloromyotomy were studied by light and electron microscopy and compared to six control cases without clinical evidence of IHPS. In certain IHPS cases degenerative alterations of the axons predominated. The axonal changes consisted of (1) severely increased variability of diameters with evidence of degeneration and regeneration of some axons, (2) accumulation of electron-dense bodies, lysosomes and pleomorphic membranous cytoplasmic bodies, (3) increase in the number of maloriented neurofilaments, and (4) aggregation of glycogen granules. Degenerative changes or immaturity of perikarya of neurons and glial cells in the myenteric plexus were not a significant feature. While axonal changes predominated in some IHPS cases there were severe changes of smooth muscle cells in others suggesting that a primarily neurogenic type of IHPS can be distinguished from a predominantly myogenic type. Although the etiology of the axonal changes in IHPS is not clear, it is suggested that they play an important role in the pathogenesis of pyloric stenosis and hypertrophy.