Congenital Aqueductal Stenosis: Findings at Fetal MRI That Accurately Predict a Postnatal Diagnosis

Sagittal balanced steady-state free precession sequence from fetal MR imaging (A) of a 33-week fetus and a postnatal sagittal T1-weighted sequence (B) of the same patient demonstrating stenosis of the inferior cerebral aqueduct with associated aqueductal funneling (arrow). As a result, there is marked enlarged of the lateral and third ventricles with dilation of the inferior third ventricular recesses (white arrowheads) depicted by bowing of the lamina terminalis and inferior third ventricular floor. The corpus callosum is thin and superiorly bowed (black arrowheads). Note also the normal size of the fourth ventricle.

Fetal MR imaging of a 30-week fetus (A) and postnatal MR imaging correlation (B) of prenatally diagnosed aqueductal stenosis with tectal thickening and loss of intercollicular sulcus (arrows). There is subtle early prominence of the supraoptic recess of the third ventricle on fetal MR imaging (white arrowhead), which progressed to more obvious dilation of both supraoptic and infundibular recesses on postnatal imaging (white arrowheads). Note also the presence of a superiorly bowed and thinned corpus callosum (black arrowheads).

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.

T2-weighted EPI sequences of 2 different fetuses with aqueductal stenosis demonstrating T2-hypointense hemorrhage within the cerebral aqueduct (A) in a 21-week fetus (white arrow) and within the lateral ventricles (B) in a 23-week fetus (black arrows).

Single-shot fast spin-echo sagittal midline (A) and axial posterior fossa (B) images in a 34-week fetus with multiple findings of dystroglycanopathy suggesting Walker-Warburg syndrome. Postnatal correlation includes a sagittal T1-weighted sequence (C) and an axial T2-weighted sequence (D). Sagittal views of both pre- and postnatal MR imaging demonstrate a hypoplastic kinked brain stem (white arrowheads) and a markedly hypoplastic cerebellar vermis. Note also the dysplastic midbrain with thickening of the tectum causing stenosis of the cerebral aqueduct (arrows). Lateral and third ventricles are markedly enlarged. Incidentally noted was a small occipital cephalocele (asterisk). Axial views show cerebellar dysplasia with irregular cerebellar margins (black arrowheads) and multiple small cerebellar cysts, which account for the increased white matter T2 signal on fetal MR imaging (asterisk). Note also a midline pontine cleft (white arrowheads in B and D), another common finding in Walker-Warburg syndrome.