Spinal Imaging Findings of Open Spinal Dysraphisms on Fetal and Postnatal MRI

Abstract

BACKGROUND AND PURPOSE: Fetal MRI has become a valuable tool in the evaluation of open spinal dysraphisms making studies comparing prenatal and postnatal MRI findings increasingly important. Our aim was to determine the accuracy of predicting the level of the spinal dysraphic defect of open spinal dysraphisms on fetal MR imaging and to report additional findings observed when comparing fetal and postnatal MR imaging of the spine in this population. MATERIALS AND METHODS: A single-center retrospective analysis was performed of fetal MRIs with open spinal dysraphisms from 2004 through 2016 with available diagnostic postnatal spine MR imaging. Images were reviewed by 2 board-certified fellowship-trained pediatric neuroradiologists. Corresponding clinical/operative reports were reviewed. RESULTS: One hundred nineteen fetal MRIs of open spinal dysraphisms were included. The level of the osseous defect between fetal and postnatal MR imaging was concordant in 42.9% (51/119) of cases and was 1 level different in 39% (47/119) of cases. On postnatal MR imaging, type II split cord malformation was seen in 8.4% (10/119) of cases, with only 50% (5/10) of these cases identified prospectively on fetal MR imaging. Syrinx was noted in 3% (4/119) of prenatal studies, all cervical, all confirmed on postnatal MR imaging. CONCLUSIONS: Fetal MR imaging is accurate in detecting the level of the spinal dysraphic defect, which has an impact on prenatal counseling, neurologic outcomes, and eligibility for fetal surgery. In addition, fetal MR imaging is limited in its ability to detect split cord malformations in patients with open spinal dysraphisms. Although rare, fetal MR imaging has a high specificity for detection of cervical spinal cord syrinx.

Prenatal and postnatal MRI findings in open spinal dysraphism following intrauterine repair via open versus fetoscopic surgical techniques

“…Defect levels are routinely reported in most cohorts for patient counseling and for determination of candidates for fetal surgery on both fetal MRI and US. In a previous publication, we carefully analyzed prenatal and postnatal MRIs in a larger cohort (both prenatal and postnatal repair patients) and found that the exact level was concordant in only 42.9% of patients with the discrepant postnatal‐level assignments falling both below (42.6%) and above (57.4%) the prenatal‐level assingments . For the purposes of this paper, we highlight a few cases describing the challenges of selecting candidates for fetal surgery with sacral spinal dysraphisms.…”

“…For the purposes of this paper, we highlight a few cases describing the challenges of selecting candidates for fetal surgery with sacral spinal dysraphisms. Given the known limitations of anatomic‐level assignment on fetal ultrasound and MRI, in addition to descriptions of fetal spine ossification with S2 being ossified by 22 weeks GA, it may be reasonable to offer fetal surgery to any open sacral spinal dysraphism regardless of the perceived level . Further advances in fetal MRI imaging with faster sequences with better spatial resolution may potentially improve level concordance in the future .…”

“…When evaluating the brain on fetal MRI, the degree of hindbrain herniation was described as grades 1 to 3 as previously described by Nagaraj et al in 2017, a modified version of a grading system initially described by Sutton et al in 1999 . When evaluating the spine, the level of the spinal dysraphic defect was determined in relation to the lumbosacral junction . The presence of a myelomeningocele, which has a measurable sac, was differentiated from a myelocele (a.k.a.…”

“…On postnatal MR imaging of the spine, the defect level was determined superior to inferior by examining the entire spine, with the odontoid being labeled C2 and assuming 7 cervical vertebral bodies and 12 thoracic vertebral bodies. The presence or absence of a measurable postoperative fluid collection (such as a pseudomeningocele), arachnoid cyst, visible spinal cord syrinx, or type II split cord malformation was also documented …”

“…There is now a growing body of literature describing both the fetal and postnatal MRI findings in this patient population, not only describing changes between presurgical and postsurgical findings but also the expected postoperative imaging appearance in these patients. There are very few imaging descriptions in the fetoscopic repair population, with one study examining postoperative growth parameters and a second study from the same group examining diffusion characteristics in patients undergoing fetoscopic repair of OSD . We present our imaging data in patients with OSD undergoing fetal surgery as well as our initial experience with preoperative and postoperative fetal MRI imaging and patients undergoing prenatal repair of OSD by both the open and the fetoscopic techniques.…”