Supplementary Material for: Relationship between brain function and microstructural brain maturation in preterm infants

Introduction: Preterm infants are at risk for impairment in brain maturation at term equivalent age (TEA). Diffusion tensor imaging (DTI) is a powerful magnetic resonance imaging (MRI) technique, quantitatively reflecting microstructural brain development of white matter regions with parameters such as fractional anisotropy (FA) and apparent diffusion coefficient (ADC). Amplitude-integrated electroencephalography (aEEG) assesses electrocortical activity and brain function. Methods: Aim of this study was to investigate a possible correlation between functional and microstructural brain maturation using neonatal aEEG and DTI-MRI at TEA. The study was conducted as a retrospective single center study in 446 infants born below 32 gestational weeks. Spearman rank´s correlation coefficients were calculated between aEEG (total maturation score) and FA/ADC value. To compare aEEG and DTI-MRI to neurodevelopmental outcome at 24 months of corrected age, we performed a multivariate linear regression analysis. Results: Analysis showed an all-time significant correlation between total maturation score and FA/ADC values of the corpus callosum at TEA with the strongest correlation at day 2, day 3, week 3 and week 4. After including perinatal variables in the model, this correlation remained highly significant at day 2 and 3. When comparing the association of aEEG and DTI-MRI to outcome, both the total maturation score at day 2, day 3 and FA/ADC of the splenium of the corpus callosum showed a significant correlation. Conclusion: This study indicates that early monitoring of functional brain maturation may predict later assessment of microstructural brain development of corpus callosum in preterm infants with a relation to neurodevelopmental outcome.