Hagmann, C.F.; (2011) Qualitative and quantitative MR imaging in preterm infants: relation to neurodevelopmental outcome. Doctoral thesis , UCL (University College London).

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Abstract

Despite improved survival of extremely preterm infants within the last two decades, long term cognitive, motor and behavioural impairment remain a significant burden for preterm born children. Motor impairment includes cerebral palsy (CP) and minor motor dysfunction occurring in 5-10% and 40% of very preterm born children respectively. A meta-analysis showed that children born preterm might manifest moderate to severe deficits in academic achievement, attention problems, internalizing problems and poor executive functions. Recent neuroimaging studies have helped to understand the nature of brain injuries in preterm infants. Various brain lesions occur in preterm infants, most commonly white matter (WM) injury and accompanying neuronal/axonal deficits that involve the cerebral WM, thalamus, basal ganglia, cerebral cortex, brainstem and cerebellum. However, precise prediction of outcome with conventional MRI is to date lacking. Quantitative MR has been mainly used to show normal and abnormal brain development, however few studies have tried to correlate quantitative MR at term equivalent age with later neurodevelopmental outcome. A better understanding of the mechanisms leading to neurodevelopmental impairment in preterm born children is critical in order to develop and monitor neuroprotective strategies. The aim of this thesis was to evaluate whether quantitative MRI at term corrected age is more predictive than conventional MRI of neurodevelopmental outcome in preterm infants. 80 preterm infants born < 32 weeks were recruited from the neonatal intensive care unit. MRI data was acquired on a Siemens (Erlangen, Germany) Avanto 1.5T scanner using the Siemens CP extremity coil. T1 weighted 3D-FLASH, T2-weighted fast spin echo, T2 relaxometry and diffusion weighted images were acquired. The infants were assessed at one and two years of age with Bayley III. Correlation between clinical data, conventional and quantitative MR findings and neurodevelopmental outcome at one and two years was evaluated with the focus on how quantitative MR measures might provide more information on outcome compared to conventional MRI. WM and GM T2 values showed significant differences between preterm subgroups and between control and preterm infants with regional variation in preterm infants. T2 values correlated well with cognitive, motor and language outcome at two years of age, even after multiple corrections for clinical and MR variables. At two years of age, caudate ADC correlated significantly with language and expressive language outcome, and periventricular frontal WM ADC correlated significantly with receptive language outcome. Splenium FA correlated with cognitive, language and receptive communication outcome at two years of age. Cognitive outcome correlated with the presence of IVH, cerebellar haemorrhage, HPI and cPVL. Small CC and DEHSI were independent risk factors for expressive language and HPI, small CC and PWML were associated with motor outcome.

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