Aqueduct stenosis

Case contributed by Dr Alexandra Stanislavsky

Presentation

Ventriculomegaly on routine second trimester morphology ultrasound.

Patient Data

Age: 22 w GA
Gender: Female
Ultrasound

Selected ultrasound images at 21 weeks gestation demonstrating bilateral ventriculomegaly, measuring 16 and 18mm. Cavum septum pellucidum is not identified.

Complete study was not available. The cerebellum and posterior fossa were reported normal. The third ventricle appeared prominent, measuring 2.5 mm.  Detailed survey of the rest of the fetal anatomy showed no additional abnormality. Female fetal gender. 

MRI

Severe bilateral lateral ventriculomegaly but the third ventricle is non dilated. The septum pellucidum is absent, with configuration of the frontal horns suggesting that this is likely due to perforation of the septal leaves rather than failed formation. Supporting this is:

  1. The severe degree of ventriculomegaly
  2. Severe thinning of the parenchyma overlying the occipital horns of the lateral ventricles consistent with increased intraventricular pressure.

Impression of a forniceal nodule suggesting the fornices are fused and that the absence of the septal leaves is therefore malformative rather than destructive. However, this appearance can be due to close approximation of two separate fornices due to limited spatial resolution of fetal MRI.

The corpus callosum is present but very thin.

The Sylvian fissures are very shallow and other sulci that should be seen at 22 weeks, namely the parieto-occipital and calcarine sulci, are not evident. This can occur when ventriculomegaly is present, especially when it is severe, due to stretching and effacement of the sulci rather than primary failure of formation.

Although there is some evidence of lamination in the hemispheric parenchyma, it is difficult to assess for normality due to the parenchyma being stretched and thinned by the enlarged ventricles.

Normal brainstem and cerebellum. Note that the ganglionic eminences are not enlarged,

Although the aqueduct of Sylvius is difficult to identify on the sagittal images this can be the case on fetal imaging when motion degradation is present and is not necessarily specific for aqueductal obstruction.

In summary, the severe lateral ventricular dilatation combined with parenchymal thinning over the occipital horns of the lateral ventricles suggests an obstructive cause for the absent septal leaves due to perforation.

Ventricular dilatation plateaued at 24 weeks. Normal vaginal delivery of healthy term infant with increased head circumference. 

MRI

Post-natal MRI aged 1 year 4 months

Typical features of aqueductal stenosis on sagittal T1 and Axial T2 weghted imaging, with dilatation of the lateral and now third ventricles.  There is thinning of the corpus callosum, especially posteriorly,  due to long term pressure effects. Note fornices have “fallen down” due to lack of support from the perforated septum pellucidum. Sulcal development is appropriate.

MRI

Follow-up MRI, aged 8 years

The degree of ventriculomegaly and ventricular morphology remains stable when compared to the MRI performed 7 years earlier.

Normal development, attending normal school, normal vison, endocrine function – followed annually by local paediatrician. Mild incoordination but no other physical or intellectual disability noted by the paediatrician who has known the child since birth.

Case Discussion

Primary aqueductal stenosis with disruption of septal leaves due to increased intraventricular pressure. Normal neurologic development after 8 years followup.

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Case information

rID: 52453
Case created: 8th Apr 2017
Last edited: 12th Apr 2017
Inclusion in quiz mode: Included

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