Cranial ultrasound and MRI at term age in extremely preterm infants.

OBJECTIVES Conventional MRI at term age has been reported to be superior to cranial ultrasound (cUS) in detecting white matter (WM) abnormalities and predicting outcome in preterm infants. However, in a previous study cUS was performed during the first 6 weeks only and not in parallel to MRI at term age. Therefore, the aim of the present work was to study brain injuries in preterm infants performing concomitant cUS and MRI at full-term age. METHODS In a population-based cohort of 72 extremely low gestational age infants paired cUS and conventional MRI were performed at term age. Abnormalities on MRI were graded according to a previously published scoring system. On cUS images the lateral ventricles, the corpus callosum, the interhemispheric fissure and the subarachnoidal spaces were measured and the presence of cysts, grey matter abnormalities and gyral folding were scored. RESULTS Moderate or severe WM abnormalities were detected on MRI in 17% of infants and abnormalities of the grey matter in 11% of infants. Among infants with normal ultrasound (n=28, 39%) none had moderate or severe WM abnormalities or abnormal grey matter on MRI. All infants with severe abnormalities (n=3, 4%) were identified as severe on MRI and cUS. CONCLUSIONS All severe WM abnormalities identified on MRI at term age were also detected by cUS at term, providing the examinations were performed on the same day. Infants with normal cUS at term age were found to have a normal MRI or only mild WM abnormalities on MRI at term age.