Magnetic resonance imaging of the brain in premature infants during the neonatal period. Normal phenomena and reflection of mild ultrasound abnormalities.

An MRI study was performed in 34 preterm infants who were clinically and neurologically normal and whose cranial ultrasound revealed no or only mild abnormalities. The postconceptional age at MRI varied between 30.6 and 37 weeks. The purpose of the study was to evaluate the significance of periventricular changes in signal intensity on MRI, comparing MRI with ultrasound. T1-weighted and T2-weighted images were assessed for changes in signal intensity of the periventricular white matter relative to the remainder of the cerebral hemispheric white matter. Cerebral MRIs of 13 postterm infants were additionally investigated. In all preterm infants small localized areas of high signal intensity on T1-weighted images and low signal intensity on T2-weighted images were seen adjacent to the frontal horns of the lateral ventricles. They faded with increasing age and were no longer seen one month after term in the group of postterm infants. The areas were considered normal before term age and probably represent remnants of the germinal matrix. Periventricular echodensities corresponded with a zone of changed signal intensity within the periventricular white matter on MRI. MRI signal change correlated with the presence and location of echodensities; the MRI signal changes slowly faded away after the echodensities disappeared.