Early myelination patterns in the central auditory pathway of the higher brain: MRI evaluation study

SummaryObjectiveThe purpose of this study was to use magnetic resonance imaging (MRI) to investigate the early myelination patterns of the central auditory pathway and then compare the data with past histological research. We observe the MRI signal intensity of the central auditory pathway and clarify the time course difference between MRI and previous histological research studies.MethodsA total of 192 infants ranging in age from −4 to 224 corrected postnatal weeks were included in the study. Images were obtained using a 1.5 T MR unit. We chose three sites (medial geniculate body, auditory radiation, and splenium of the corpus callosum) of the central auditory pathway for analysis. Three cross sections were obtained perpendicular to the long axis of the brain and used to analyze the signal changes of the T1- and T2-weighted MRI by employing a region-of-interest (ROI) methodology that was corrected for postnatal age.ResultsAt 10 corrected postnatal weeks, the medial geniculate body showed myelinated intensity changes on T2-weighted images. Auditory radiation showed myelinated intensity changes at 19 corrected postnatal weeks on the T1-weighted images and at 24 corrected postnatal weeks on the T2-weighted images. The splenium of the corpus callosum showed myelinated intensity changes at 16 corrected postnatal weeks on T1-weighted images and at 24 corrected postnatal weeks on T2-weighted images.ConclusionsAs compared to the histological literature, the MRI documented signal intensity changes caused by myelination occurred approximately 3 weeks later for the medial geniculate body, 7–24 weeks later for the auditory radiation and 7–15 weeks later for the splenium of the corpus callosum. Since myelination is a process that occurs gradually, substantial changes of the myelin sheath makeup, a loss of water and the addition of lipids are more required in order to be detectable by MRI than myelin staining of histological study.