Fetal MRI of CNS abnormalities

Ultrasound (US) is currently the standard approach for the initial evaluation of fetal anatomy and maternal conditions during pregnancy; however, fetal magnetic resonance imaging (MRI) has now become a valuable adjunct to US in confirming/excluding suspected abnormalities and in the detection of additional abnormalities, thus changing the outcome of pregnancy and optimising perinatal management. MRI is a non-invasive diagnostic examination that does not involve ionising radiation and has no known associated negative side effects or reported delayed sequela according to the Safety Committee of the Society for MRI. The main drawback of MRI is fetal motion. The development of fast MRI sequences has significantly decreased fetal motion artefacts allowing the evaluation of the highly mobile fetus. Single-shot fast spin-echo (SSFSE) T2-weighted imaging is a standard sequence. T1-weighted sequences are primarily used to demonstrate haemorrhage, fat, and calcification. Balanced steady-state free-precession (SSFP) sequences are beneficial in demonstrating fetal structures as well as the heart and vessels. Diffusion-weighted imaging (DWI) and magnetic resonance spectroscopy (MRS) have important applications in fetal brain imaging. In this review, we illustrate a spectrum of structural abnormalities affecting the central nervous system and the spine. The aim of this article is to provide a practical approach for radiologists and clinicians to fetal MRI performance and interpretation.