Hindbrain Herniation in Chiari II Malformation on Fetal and Postnatal MRI

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The authors examined the neuroimaging findings with a focus on hindbrain herniation and ventricular size in fetuses with open spinal dysraphism and compared them with postnatal imaging features in groups undergoing prenatal-versus-postnatal repair. Thirty-two of 102 (31.3%) fetuses underwent in utero repair of open spinal dysraphism; 68.6% (70/102) underwent postnatal repair. Of those who underwent prenatal repair 81.3% (26/32) had resolved cerebellar ectopia postnatally. Of those who had severe cerebellar ectopia (grade 3) that underwent postnatal repair, 65.5% (36/55) remained grade 3, while 34.5% (19/55) improved to grade 2. They conclude that most fetuses who undergo in utero repair have resolved cerebellar ectopia postnatally.

Abstract

Figure 2 from paper
A and B, Sagittal T2 SSFSE from fetal MR imaging performed at 24 weeks’ and 5 days’ gestational age (A) demonstrates severe cerebellar ectopia or grade 3 Chiari II malformation (arrow). Note that there is also effacement of the prepontine cistern and extra-axial CSF spaces over the cerebral hemispheres. Sagittal T2 FSE from postnatal MR imaging of the same patient at 2 weeks of age after postnatal repair of OSD shows a persistent grade 3 Chiari II malformation (arrow).

BACKGROUND AND PURPOSE

As the practice of in utero repair of myelomeningoceles becomes more prevalent, knowledge of the expected MR imaging findings has become increasingly important. Our aim was to examine neuroimaging findings with a focus on hindbrain herniation and ventricular size in fetuses with open spinal dysraphism and to compare them with postnatal imaging features in groups undergoing prenatal-versus-postnatal repair.

MATERIALS AND METHODS

Single-center retrospective analysis was performed on MRIs of fetuses with open spinal dysraphism from January 2004 through July 2015 with available postnatal imaging. One hundred two fetuses were included. Reports from available fetal ultrasound were also examined. Images were reviewed by 2 board-certified fellowship-trained pediatric neuroradiologists. Descriptive analyses were performed to demonstrate the distribution of the imaging findings.

RESULTS

Thirty-two of 102 (31.3%) fetuses underwent in utero repair of open spinal dysraphism; 68.6% (70/102) underwent postnatal repair. Ninety-four of 102 (92.2%) fetuses had cerebellar ectopia. Of those who underwent prenatal repair (26 grade 3, 6 grade 2), 81.3% (26/32) had resolved cerebellar ectopia postnatally. Of those who had severe cerebellar ectopia (grade 3) that underwent postnatal repair, 65.5% (36/55) remained grade 3, while the remaining 34.5% (19/55) improved to grade 2. The degree of postnatal lateral ventriculomegaly in those that underwent prenatal repair (20.3 ± 5.6 mm) was not significantly different from that in those that underwent postnatal repair (21.5 ± 10.2 mm, P = .53). Increased Chiari grade was significantly correlated with decreased head size for gestational age on fetal sonography (P = .0054).

CONCLUSIONS

In fetuses with open spinal dysraphism and severe Chiari II malformation that do not undergo prenatal repair, most have no change in the severity of cerebellar ectopia/Chiari grade. However, in fetuses that undergo in utero repair, most have resolved cerebellar ectopia postnatally.

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Hindbrain Herniation in Chiari II Malformation on Fetal and Postnatal MRI
Jeffrey Ross
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