Reliability of MR Imaging–Based Posterior Fossa and Brain Stem Measurements in Open Spinal Dysraphism in the Era of Fetal Surgery

Abstract

BACKGROUND AND PURPOSE: Fetal MR imaging is part of the comprehensive prenatal assessment of fetuses with open spinal dysraphism. We aimed to assess the reliability of brain stem and posterior fossa measurements; use the reliable measurements to characterize fetuses with open spinal dysraphism versus what can be observed in healthy age-matched controls; and document changes in those within 1 week after prenatal repair. MATERIALS AND METHODS: Retrospective evaluation of 349 MR imaging examinations took place, including 274 in controls and 52 in fetuses with open spinal dysraphism, of whom 23 underwent prenatal repair and had additional early postoperative MR images. We evaluated measurements of the brain stem and the posterior fossa and the ventricular width in all populations for their reliability and differences between the groups. RESULTS: The transverse cerebellar diameter, cerebellar herniation level, clivus-supraocciput angle, transverse diameter of the posterior fossa, posterior fossa area, and ventricular width showed an acceptable intra-and interobserver reliability (intraclass correlation coefficient Ͼ 0.5). In fetuses with open spinal dysraphism, these measurements were significantly different from those of healthy fetuses (all with P Ͻ .0001). Furthermore, they also changed significantly (P value range ϭ .01 to Ͻ .0001) within 1 week after the fetal operation with an evolution toward normal, most evident for the clivus-supraocciput angle (65.9 Ϯ 12.5°; 76.6 Ϯ 10.9; P Ͻ .0001) and cerebellar herniation level (Ϫ9.9 Ϯ 4.2 mm; Ϫ0.7 Ϯ 5.2; P Ͻ .0001). CONCLUSIONS: In fetuses with open spinal dysraphism, brain stem measurements varied substantially between observers. However, measurements characterizing the posterior fossa could be reliably assessed and were significantly different from normal. Following a fetal operation, these deviations from normal values changed significantly within 1 week. ABBREVIATIONS: ACi ϭ atriocerebral index; CHL ϭ cerebellar herniation level; CSA ϭ clivus-supraocciput angle; GA ϭ gestational age; ICC ϭ intraclass correlation coefficient; OSD ϭ open spinal dysraphism; PF ϭ posterior fossa; TCD ϭ transverse cerebellar diameter; TDPF ϭ transverse diameter of the PF; VW ϭ ventricular width

Biometric assessments of the posterior fossa by fetal MRI: A systematic review

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

“…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.…”