MAGNETIC-RESONANCE-IMAGING OF THE BRAIN IN VERY PRETERM INFANTS - VISUALIZATION OF THE GERMINAL MATRIX, EARLY MYELINATION, AND CORTICAL FOLDING

Objective. To investigate preterm infants, we have installed in our ne onatal intensive care unit a dedicated magnetic resonance (MR) imaging system which was specifically designed for neonatal use. The aim of t his study was to describe the MR appearances of the brain in preterm i nfants who were first scanned between 25 and 32 weeks gestational age (GA) and to outline changes to the brains of these infants between the ir first scan and term. Methods. Preterm infants of 25 to 32 weeks GA were imaged using the IT neonatal MR system (Oxford Magnet Technology, Eyensham, Oxfordshire, England/Picker International, Cleveland, OH). The scanning protocol included T1-weighted conventional spin echo (rep etition time [TR], 600; echo time, 20 ms), inversion recovery fast spi n echo (TR, 3530; effective echo time, 30; inversion time, 950 ms), an d Ta-weighted fast spin echo (TR, 3500; effective echo time, 208 ms) s equences. Results. Seventeen infants of median 28 weeks GA (lange, 24 to 31 weeks) at birth were imaged a total of 53 times between birth an d term. The median number of images per infant was two (range, 1 to 9) . In infants of <30 weeks GA, the germinal matrix was visualized at th e margins of the lateral ventricles. It had a short T1 and short T2 an d the bulk of it involuted at between 30 and 32 weeks GA. The white ma tter had a relatively homogeneous low signal except for bands of alter ed signal (probably originating from regions containing radial glia an d migrating cells) which were most apparent anterolateral and posterol ateral to the lateral ventricles. Myelination was seen in the posterio r brainstem, cerebellum, and region of the ventrolateral nuclei of the thalamus. Infants had very little cortical folding at 25 weeks GA. bu t this developed later in an orderly fashion. Conclusion. The neonatal MR system allowed extremely preterm infants to be studied safely with MR imaging. The images acquired demonstrated the germinal matrix, ear ly myelination, and early cortical folding. Evolution of these feature s was demonstrated with serial studies.