MR features of the developing perianterior horn structure including subcallosal fasciculus in infants and children

Introduction To describe the changes in the magnetic resonance (MR) signal of the perianterior horn structure (PAS) with increasing age, we studied 69 infants and children aged between 3 days and 9.4 years (average: 2.8 years) without any neurological deficits. Methods T1- and T2-weighted images and FLAIR (fluid attenuation inversion recovery) images were obtained in the axial plane. Based on a comparison of the intensity of the PAS with that of the cortex in each sequence (T1-WI/FLAIR/T2-WI), we classified the signal-intensity patterns into four types: I, low/low/high; II, low/high/high; III, iso/high/high; IV, high/low/low. Results Signal-intensity types I, II, III and IV were seen in 22, 8, 17, and 22 subjects, respectively, with younger subjects showing type I or II intensity patterns and older subjects showing type III or IV. In addition, T1-weighted and FLAIR images of subjects with a type I intensity pattern showed a rim of an isointensity component around the PAS that histologically coincided with migrating glial cells. The low-intensity area on FLAIR and T2-WI images of subjects with a type IV intensity pattern may represent myelinated fibers of the subcallosal fasciculus (ScF). Conclusion The intensity of the MR signals of the PAS changes with increasing age, and this change may reflect histological features. A better understanding of these characteristics may help us to clarify myelination abnormalities, particularly those related to the ScF in the frontal lobe in infants and children.