ALTERED RATIO BETWEEN AXON CALIBER AND MYELIN THICKNESS IN SURAL NERVES OF CHILDREN

Abstract

Maturation of myelin sheaths in normal sural nerves of children proceeds more slowly than axon growth. This asynchronous development of axons and myelin sheaths results in a statistically significant change of the ratio between axon caliber and myelin thickness during normal development. Therefore, myelin thickness of individual nerve fibers must be related to the size of the axons as well as to the age of the individuals studied. Abnormalities of the relationship between myelin thickness and axon diameter (primary hypomyelination of large, or small, or all fibers) were clearly identified in cases with metachromatic leukodystrophy, KRABBE's, DEJERINE.SOTTAS’, COCKAYNE'S and SANFILIPPO's disease, and in children with malignant neoplasms. A striking reduction of axon diameters was seen in a unique case with congenital, total absence of central and peripheral myelin. On the other hand, in GM2 gangliosidosis and ceroid lipofuscinosis no such disturbances were detected despite storage of pathologic material in Schwann cells.