Presented at the Neonatal Society 2005 Autumn Meeting.
Perkins L1, Hughes E2, Glover A2, Kumar S3, Rutherford M1
1 Imaging Sciences Department, Clinical Sciences Centre, Imperial College, London W12, UK
2 Department of Radiology, Hammersmith Hospital, London W12, UK
3 Centre for Fetal Care. Hammersmith Hospital, London W12, UK
Objective: To investigate the potential of using fetal MRI to document, in vivo, the evolution of the subplate, a transient layer of the developing cortex which until now has been restricted to in vitro exploration (1).
Method: Ethical approval for these studies was obtained from the Hammersmith Hospital Ethics Committee. Investigation centred on two-dimensional measurements of intraparenchymal laminar diameters, in ten regions of interest, using clinical T2-weighted MRI images from twenty-six single foetus pregnancies ranging from 20 to 35 weeks gestational age. Bi-parietal diameter, ventricular diameter and germinal matrix were also assessed. The coefficient of variability for all measurements was between 0.14 and 1.87%.
Results: At 20 weeks gestation the subplate is visible globally as a thick band of characteristic high intensity, subjacent to the developing cortical plate. A distinctive pattern of development follows, diameter peaking around 29 weeks, before becoming increasingly isodense to neighbouring layers, restricted to gyral crests and finally MRI invisible. Regional variation in the timing of these events was evident. Cortical plate diameter appeared constant throughout.
Discussion: The developmental course observed correlates with that established using in vitro investigation. In common with other aspects of brain development subplate maturation occurs earlier in primary cortical areas, with association cortex lagging behind.
Conclusion: Fetal MRI can indeed be used to qualitatively and quantitatively analyse subplate development, providing a potential means of assessing cortical developmental disturbances antenatally. Comparison of subplate evolution in the normal fetus with the postnatal evolution in the preterm infant may allow insights into the neurocognitive impairments in children born preterm.
References
1. Kostovic I et al. Cereb Cortex. 2002;12:536-44.