• Vol. 38 No. 9, 774–781
  • 15 September 2009

Magnetic Resonance Imaging of the Fetal Central Nervous System in Singapore

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ABSTRACT

Introduction: Fetal imaging has improved with the development of faster magnetic resonance imaging (MRI) sequences, obviating the requirement for sedation. It is useful in characterising abnormality of the central nervous system in fetuses with abnormal or equivocal antenatal ultrasound findings. We reviewed all cases of fetal brain and spine MRI performed in our institution. Materials and Methods: All cases of fetal central nervous system MRI imaging from May 2006 to December 2008 were retrospectively reviewed, including fetal MRI, postnatal MRI and autopsy findings. Results: Thirty-one fetuses were imaged with MRI for evaluation of the central nervous system of which 3 were specifically for spinal evaluation. On fetal MRI, there were 11 normal fetuses (2 with minor ventricular asymmetry), 4 fetuses with minor ventriculomegaly and 16 fetuses with significant abnormalities. Twenty-three fetuses were delivered and 8 were terminated. Fifteen of 23 babies underwent postnatal imaging, 21 had clinical follow-up and 2 were lost to clinical follow-up. Of the 11 fetuses reported as normal on fetal MRI, 3 had additional postnatal findings. A fetus with a megacisterna magna on fetal MRI was diagnosed with a posterior fossa arachnoid cyst on postnatal MRI. One, who had fetal MRI to assess suspected absent inferior cerebellar vermis, had intracranial calcifications from rubella infection. One was diagnosed with cerebro-occular-facio-skeletal (COFS) syndrome postnatally, 1 was lost to follow-up and the rest were discharged well. Seven out of 16 fetuses with significantly abnormal fetal MRI findings had confirmation of the findings on postnatal imaging. Postnatal MRI detected 2 cases of polymicrogyria which were not seen on fetal MRI. Autopsy was available in 1 abortus confirming intrauterine diagnosis of Dandy Walker malformation. A myelomeningocele was clinically obvious in 1 abortus. Conclusion: Fetal MRI is a good method of assessing brain and spine abnormalities in utero. However, disorders of neuronal migration remain a challenging diagnostic problem in fetal imaging.


Fetal magnetic resonance imaging (MRI) has been performed for 2.5 decades,1 with fetal motion being a limiting factor in early studies. With the introduction of the faster MRI sequences such as the half-Fourier acquisition single-shot turbo spin echo (HASTE) sequence which can obtain images in just 430 milliseconds,2 sedation is no longer required for diagnostic images. Although other fast MRI sequences have been utilised in fetal MRI,3 HASTE and single-shot fast spin echo (SSFESE) T2 remain the mainstay of fetal MRI.4 Real time MRI5 allows almost continuous imaging of the moving fetus, using the freshly acquired set of images for orientation, obviating the need for additional scouts and thus improving the efficiency of imaging a moving fetus. No adverse effects have been described on the fetus with a magnet strength of 1.5 Tesla or less.6,7

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