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Rhombencephalosynapsis, Fetal Imaging

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This is a fetal ultrasound performed

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at 29 weeks gestation,

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and it shows profound ventriculomegaly.

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We can actually see dangling choroid plexus.

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And this was further characterized with fetal MR.

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That fetal MR shows massive enlargement of

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both lateral ventricles.

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We scroll inferiorly.

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The third ventricle is on the bigger side.

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The fourth ventricle is not enlarged.

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If we look at this sagittal image,

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we see the massive enlargement

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of the lateral ventricles.

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There's enlargement of the third ventricle.

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And if I zoom in,

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I can actually see the superior aspect of

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the aqueduct of sylvius looks patent.

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We're not seeing it inferiorly.

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And while this is a very small structure,

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the fact that we have a tri ventricularmegaly,

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both lateral ventricles and the third ventricle

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without an abnormality of the fourth ventricle,

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or at least without enlargement

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of the fourth ventricle,

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suggests that the aqueduct of Sylvius is a likely

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location for an abnormality of CSF flow.

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Now, there's another finding that we see.

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The cerebellar vermis has an unusual configuration,

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including an abnormal configuration of

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the nondilated fourth ventricle.

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If we look on this image,

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we're actually in axial image of the posterior fossa.

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We're not seeing a cerebellar vermis,

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and we're seeing sort of a rounded appearance

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of the posterior aspect of the cerebellum.

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That, to me,

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is suggestive of rhombencephalosynapsis.

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Obviously,

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we want to confirm this with postnatal imaging,

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but this is suggestive of rhombencephalosynapsis.

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And why does this make sense?

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Well,

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rhombencephalosynapsis can be associated with

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a congenital aqueductal stenosis.

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That congenital aqueductal stenosis is felt to be

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related to abnormal transverse migration

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of the inferior colliculi,

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resulting in something that could be

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referred to as mesencephalon synapses.

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So in patients with aqueductal stenosis,

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always pay attention to the cerebellar vermis,

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and you may actually find that there's also

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associated rhombocephalus synapses.

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That may then

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allow appropriate referral to genetics for

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evaluation of other genetic abnormalities.

Report

Description

Faculty

Asim F Choudhri, MD

Chief, Pediatric Neuroradiology

Le Bonheur Children's Hospital

Tags

Ultrasound

Spine

Pediatrics

Neuroradiology

Musculoskeletal (MSK)

MRI

Idiopathic

Congenital

Brain

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