Age-related changes in the posterior limb of the internal capsule revealed by magnetic resonance imaging.

In this study, we examined the age-related differences in the corticospinal tract (CST) of the posterior limb (PL) of the internal capsule (IC) by analyzing 53 magnetic resonance (MR) images from 45 subjects. Regions in the posterior part of the PL of the IC were observed as hypointense areas in T1-weighted images of axial sections at 4 years of age. These regions became clear, spotty hyperintense areas in T2-weighted images of subjects older than 9 years. These regions persisted in all cases beyond 9 years of age, level on both T1- and T2-weighted images. The region is consistent with the CST from MR images of coronal and sagittal sections in our study. These results suggest that differences among the region may occur, such as an increase in fiber size and an increase in the thickness of the myelin sheaths, depending on age after the completion of general myelination in the CST.