Fetal MRI in the Evaluation of Intrauterine Myelomeningocele

Abstract

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.

Clinical Significance of Prenatal and Postnatal Heavily T2-Weighted Magnetic Resonance Images in Patients with Myelomeningocele

“…Determination of the level of the lesion on fetal MR images is indispensable as it informs the counseling of parents about the likelihood of their child having shunt-dependent hydrocephalus and his or her likely leg function; furthermore, it guides treatment strategy, which may include termination of pregnancy, conventional postnatal closure or intrauterine repair [20,21,22,23]. We found that prenatal MR images were suitable for these purposes, in agreement with other investigators [1,3,5,17,24,25,26,27,28,29]. The presence of a skin defect and enlarged CSF space on prenatal MR images allowed the diagnosis to be made without difficulty and the approximate level of MMC to be established in all cases.…”

“…The presence of a skin defect and enlarged CSF space on prenatal MR images allowed the diagnosis to be made without difficulty and the approximate level of MMC to be established in all cases. As Mangels et al [28] commented, the resolution of the images obtained is generally good, but does not provide sufficient detail for individual vertebral bodies to be differentiated and thus for the anatomic level or morphology of the spinal dysraphism to be identified. It has previously been reported that fetal MR imaging can lead to the misdiagnosis of the spinal level by up to 2 levels in 20% of cases [1].…”

Congenital Craniopharyngioma: A Role for Imaging in the Prenatal Diagnosis and Treatment of an Uncommon Tumor

“…Indeed, definition of the extent of brain injury secondary to the growth of the tumor suggested that a successful surgical result would not have resulted in a favorable functional outcome. Fetal repair of congenital spinal cord abnormalities such as myelomeningoceles [32], has been shown to be a safe procedure that improves specific outcomes such as rate of shunt insertion [33]. It is hoped that technical advances will allow development of surgical techniques that may permit fetal surgery for complex problems such as congenital brain tumors.…”

Fetal Myelomeningocele Closure: Technical Considerations

“…Imaging studies are useful in surgical planning [7,8,9]. The fetus with a wide defect and no sac (myeloschisis) may present difficulty in closing the skin, and a graft may be required and should be available and prepared.…”