Purpose or Case Report: Open spinal dysraphism occurs as a consequence of failed neurulation during embryological development and includes two subtypes, myelomeningocele and myelocele. Intrauterine fetal repair can result in reversal of the associated Chiari II malformation and is now considered a treatment option.
The main imaging method for prenatal detection, management, and monitoring of open neural tube defects is US, but MRI is essential for the preoperative assessment, indications and workup for fetal surgery, and postnatal follow-up. This prospective study describes the contribution of MRI in this clinical scenario.
Methods & Materials: Fourteen fetuses underwent prenatal closure of myelomeningocele (9) or myelocele (5) over the last 5 years. Gestational age was below 27 weeks (19-26 weeks). The first 7 fetuses underwent surgery using a conventional laparotomic approach, whereas a fetoscopic approach was used in the last 7 fetuses.
Prenatal MR images were obtained on a 1.5T system (Avanto; Siemens, Erlangen, Germany), using a phased array abdominal coil. Axial, sagittal, and coronal HASTE, T1 fast low-angle shot (GRE), axial T2 GRE, and axial DWI sequences were part of the routine examination of the fetal spine and brain. Fetal sedation was not used. All cases were examined at least 3 times by MR imaging: preoperatively, immediately after prenatal surgery, and postnatally. All MR images were interpreted by at least 2 experienced pediatric neuroradiologists.
Results: The assignment of lesion level, verification of Chiari II, and ventricular size were similar by prenatal US and MRI. The main contribution of prenatal MRI was to confirm or exclude the indication for surgery.
During postoperative prenatal MRI some relevant parameters were analyzed, including posterior fossa size and lower cerebellar position, visualization of the 4th ventricle and CSF posterior fossa spaces, improvements in ventricular size, and presence or not of adequate coverage of the neural defect. Confirmation of this last factor was the most challenging task for MRI.
Postnatal MRI can clarify patch-related fistula, need for VP shunt, and postnatal Chiari status.
Conclusions: Recent advances in fetal repair of open neural defects, such as earlier closure in gestation and development of less invasive approaches, require parallel improvements in the fetal MRI technique.
The information provided by MR imaging beyond US findings makes MR essential in the workup and follow-up of intrauterine repair of open neural tube defects.