PMC4899545_01
Sagittal (A) and axial (B) sonographic images show prominent fourth ventricle (arrow) and retrocerebellar CSF space (arrowhead).
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Routine prenatal sonography of a 25-year-old pregnant female at 25 weeks' gestation revealed a retrocerebellar cystic area that communicated with a prominent fourth ventricle (Figs. 1A, B).
Prenatal axial (A, B) and sagittal (C, D) MRI images show prominent fourth ventricle (arrow), elevation of superior medullary velum (open arrow), and prominent retrocerebellar CSF space (arrowhead).
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Fetal MRI performed two days later showed a prominent fourth ventricle, elevation of superior medullary velum, an appropriate-sized vermis, and bilateral cerebellar hemispheres (Figs. 2A-D).
Postnatal sagittal (A) and axial (B, C) MRI images show unremarkable fourth ventricle (arrow), vermis (arrowhead), and retrocerebellar CSF space (open arrow).
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Postnatal MRI of the neonate showed regression of the retrocerebellar CSF collection (Figs. 3A-C).