NMR intensity of corpus callosum differs with age but not with diagnosis of autism.

NMR signal intensities in five regions of the midsagittal corpus callosum were measured in autism patients and normal controls. An age-related increase in signal was observed in the anterior regions in both groups. No significant differences in intensity were detected between the groups. The finding of normal myelination supports the attribution of callosal narrowing to absence of axons rather than absence of myelin.