Differentiating Closed Versus Open Spinal Dysraphisms on Fetal MRI.

OBJECTIVE: The purpose of this study is to identify differences in findings between open and closed spinal dysraphisms seen on fetal MR images.

MATERIALS AND METHODS: A single-institution retrospective analysis of fetal MR images for spinal dysraphism was performed. Postnatal images and clinical and operative reports were reviewed.

RESULTS: Sixteen fetuses with postnatally confirmed closed spinal dysraphisms were included. Of these, 25% (4/16) had posterior fossa anomalies, 12.5% (2/16) had ventriculomegaly, and 37.5% (6/16) had OEIS (omphalocele, exstrophy, imperforate anus, and spinal defects) complex. Of 90 fetuses with postnatally confirmed open spinal dysraphism, 95.6% (86/90) had posterior fossa anomalies, 85.6% (77/90) had ventriculomegaly, and none had OEIS complex. Twenty fetuses with open spinal dysraphism were randomly selected to compare with fetuses with closed spinal dysraphisms. Continuity of the epidermal and subcutaneous tissues with the sac wall on fetal MR images was seen in 93.8% (15/16) of patients with closed spinal dysraphisms, as opposed to 5% (1/20) of patients with open spinal dysraphisms. The mean (± SD) sac wall thickness was less in open (0.7 ± 0.6 mm) than closed (2.9 ± 1.3 mm; p < 0.001) spinal dysraphism. None of the fetuses had T1-hyperintense fat within the defect.

CONCLUSION: On fetal MR images, closed spinal dysraphisms tend to have a sac wall in continuity with the epidermal and subcutaneous tissues, a thicker sac wall, fewer posterior fossa anomalies, and high association with OEIS complex.