MR features of developing periventricular white matter in preterm infants: evidence of glial cell migration.

PURPOSE: MR imaging of the brain is increasingly used in the investigation of the newborn, but little information is available on the normal appearance of the developing brain. We scanned a series of newborn infants in an attempt to define the normal appearance of developing periventricular white matter and to assess how pathologic conditions may modify this appearance.
METHODS: Sixty-eight newborn infants, median postmenstrual age (PMA) 34 weeks (range, 24 to 42 weeks), were subdivided into two groups: group A (n = 33), which included those with normal clinical and sonographic examinations, and group B (n = 35), which contained those with evidence of neuroabnormality detected prior to the MR study, either clinically or by cerebral sonography. Images were acquired in two planes on a 1.5-T imager using turbo spin-echo pulse sequences.
RESULTS: Symmetric periventricular bands of reduced signal intensity were noted in the frontal periventricular white matter on T2-weighted images in 98% of group A infants and in 97% of group B infants. The number of bands was inversely related to PMA. The reduction in number of bands with increasing PMA was delayed in group B infants.
CONCLUSION: The uniform appearance of periventricular bands in a population of healthy infants and their relationship to the infants' maturity is consistent with the results of previous histologic studies. These studies demonstrate the presence of migrating glial cells within the periventricular white matter of infants beyond 20 weeks' gestation, when neuronal migration to the cortex is complete. We postulate that the bands seen on T2-weighted images represent groups of migrating glial cells, providing a further marker of cerebral maturation.