Fetal MRI in the evaluation of intrauterine myelomeningocele.

BACKGROUND: Accurate fetal imaging is essential to the practice of maternal-fetal medicine. While ultrasonography has been the traditional mainstay of fetal imaging, its ability to resolve critical features of central nervous system (CNS) anatomy remains limited. As interest in intrauterine therapy for myelomeningocele has increased, so has the need for more accurate, noninvasive imaging of the CNS. Fetal magnetic resonance imaging (MRI) promises to fill the gap left by ultrasound.

METHODS: Thirty-seven MRI scans of fetuses previously diagnosed with myelomeningocele were reviewed by 2 neuroradiologists. The ability of fetal MRI to resolve the commonest CNS stigmata of spina bifida, and the incidence and extent of interobserver error, was assessed. In 4 cases, postnatal MRIs were also available. These were compared to the corresponding fetal studies.

RESULTS: The imaging quality with the technique used in this study was excellent, even without the use of maternal or fetal sedation. There were no complications, and the imaging times were minimal. Interobserver error was minimal with respect to the evaluation of ventricular dilatation and hindbrain herniation, but moderate in the description and location of the spinal lesion. As had previously been documented with ultrasonography, a reduction was seen in hindbrain herniation when comparing pre- and postnatal MRIs.

CONCLUSION: It is concluded that fetal MRI is an effective, noninvasive means of assessing fetal CNS anatomy. Its ability to resolve posterior fossa anatomy is superior to ultrasonography while, with respect to the evaluation of hydrocephalus and the level and nature of the spinal lesion, it may be equivalent to inferior. Inclusion of the fetal MRI into the standard diagnostic armamentarium will probably await the next major advance in speed and resolution. It is conceivable that, with further advances, MRI might supplant ultrasonography as the diagnostic tool of choice for evaluation of fetal anomalies including myelomeningocele.