Fig 4.

A single-shot fast spin-echo sequence in the axial planes (A and B) through the fetal head in a 23-week fetus and postnatal axial T2-weighted sequence (C and D) demonstrate asymmetric lateral ventriculomegaly with focal parenchymal disruption resulting in a posterior ventricular diverticulum (black arrowheads). Note also perforation of the septum pellucidum in A and C (arrow). Within the posterior fossa (B and D), there are a small transverse cerebellar diameter, absence of the cerebellar vermis, midline fusion of cerebellar folia, and a convex posterior cerebellar contour (white arrowheads), compatible with rhombencephalosynapsis.