Hindbrain Herniation in Chiari II Malformation on Fetal and Postnatal MRI

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).

Sagittal T2 FSE from postnatal MR imaging in the same patient as in Fig 1A, status post postnatal repair of OSD at 11 days of age again demonstrates no cerebellar ectopia (arrow). Note the presence of other intracranial findings of a Chiari II malformation, including callosal hypogenesis/dysgenesis, a thickened massa intermedia, and tectal beaking.