Measuring neural development in premature babies

Children born prematurely are more likely to display signs of neurodevelopmental impairment, often manifest as cognitive deficits, lower academic performance than their peers, and behavioural problems such as attention deficit hyperactivity disorder.

Conventional MRI has so far failed to detect structural abnormalities that can fully account for the impairment seen in these cases. However, there have been indications that structural deficits in brain white matter, suggested by diffuse signals from the tissue in preterm individuals, are linked to neurological impairment.

Serena Counsell of the CSC’s Imaging Physics and Engineering Group led research published in Brain, which demonstrated a link between the directional dependence of water diffusing in brain white matter and neurodevelopmental impairment in two-year old children born prematurely. The technique used, called diffusion tensor imaging, measures Brownian motion of water in tissue: Water moves more freely along white matter fibres than across them. Previous work had shown that the degree of directional dependence of water diffusing in white matter, termed the ‘FA’ (fractional anisotropy) value, increases during adolescence and can be correlated to increased working memory and reading age. FA values are indicators of the tissue microstructure of brain white matter, being dependent on fibre coherence, axonal density, cell membrane and myelination.

Counsell and coworkers have shown that FA values in two-year olds, all born preterm (median birth at 28 weeks), correlate to their performance the Griffiths mental development scale, which measures a number of factors including cognitive performance and hand-eye coordination. Lower FA values were associated with a lower performance score.

The incidence of preterm birth in developed countries is increasing while mortality rates are also falling. It is hoped that early assessment using FA as an indicator may assist in prognosis and that FA can be used as a biomarker for therapeutic studies.

Stefan Janusz

This work was published in Brain