Assessment of infant physiology and neuronal development using magnetic resonance imaging

Previous work has demonstrated both that there are substantial individual differences in the rate of physiological development,and that infants with risk factors for Sudden Infant Death Syndrome (SIDS) develop more slowly, suggesting that their increased vulnerability may be due to delayed neuronal development associated with compromised development in fetal or early neonatal life. This project aims to test the hypothesis that individual differences in the rate of physiological development of infants correlate with measurable differences in the rate of brain development as assessed by magnetic resonance imaging (MRI). Sixty infants were recruited to this study in three different groups that are known to have differing rates of physiological development. MRI was performed successfully in 49 cases at 6 weeks of age without sedation. Forty-one of these cases had full follow-up (15 normal; 19 IUGR; 11 'high risk'). Postnatal physiological development was assessed by measuring age-related deep body temperature patterns during sleep. Neuronal development was assessed by subjective analysis of MRI images and objective measurements relating to myelination using T1 and diffusion weighted (23 cases) MRI images. As expected the normal group acquired the adult temperature pattern earlier, but this was not statistically significant. All MRI scan appearances were within normal limits. Ranking cases subjectively in order of maturity revealed no significant pattern. The normal group had a significantly higher myelination score than the IUGR and 'high risk' groups (P = 0.001). This trend was also shown by the diffusion weighted myelination score but did not reach statistical significance. No significant differences were seen in both the subjective and objective MRI measurements and development of nocturnal temperature patterns. The results suggest there may be differences in neurodevelopment between the different groups at 6 weeks of age but these are not linked to late development of temperature patterns. It is therefore unlikely that this related to a global delay in maturation.