106 Cortical Growth and Neurocognitive Impairment in Preterm Infants

Abstract

Background. Neurocognitive impairment after preterm birth is common and directly related to increasing prematurity. The neural substrate for this dysfunction is unknown, but cannot be wholly accounted for by major destructive brain lesions.Aims. To test the hypothesis that the timing of premature delivery is associated with a dose-dependent reduction in the rate of growth of the cerebral cortex which parallels the increase in neurocognitive impairment.Methods. MR images were obtained from a consecutive cohort of extremely preterm infants serially from soon after delivery until term corrected age and neurodevelopment was assessed using the Griffiths Developmental Scales at median 24 months corrected age. Total cerebral volume and cortical surface area were measured semi-interactively, and their rate of growth found to be related by a power law, the scaling exponent of which gives a direct measure of the growth rate of cortical surface area relative to cerebral volume. A generalized least squares random effects regression model was constructed to test the effect of gestational age at birth and potential confounding variables on the scaling exponent, and the relation to neurodevelopmental outcome was tested.Results. 113 infants born at 23–29 weeks gestation were imaged providing 274 images without major destructive lesions for analysis. Complete neurodevelopmental data are available on 63 infants. Increasing prematurity was associated with a reduced rate of cortical growth (p<0.0001) which was independent of intrauterine or postnatal somatic growth. There was a significant relation between reduced cortical growth and the Griffiths Developmental Quotient (p<0.05), seen with all subscales except the locomotor.Conclusions. Reduced rate of growth of the cerebral cortex parallels the dose-dependent effect of prematurity on neurodevelopmental function. Cortical growth failure may be a neural substrate for the high rate of non-locomotor neurocognitive impairment seen in preterm infants.