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This is an MRI of a 13-month-old child with

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a known lumbosacral meningomyelocele.

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And we know that a lumbosacral meningomyelocele

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has essentially a 100% association with an

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intracranial Chiari type II malformation.

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So,

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this MRI, sagittal T1-weighted image, shows

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we see a vertically oriented,

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very small in caliber fourth ventricle.

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We see an abnormal appearance of the cerebellar

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vermis and cerebellar ectopia,

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which includes the cerebellar tonsils

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and the cerebellar vermis.

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We will confirm that on the axial images,

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you can see

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cerebellar tonsils and the cerebellar vermis

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extending down into an enlarged foramen magnum.

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We're seeing several other features.

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We're seeing a large massa intermedia.

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We're seeing somewhat of a beaked appearance or

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posteriorly pointing appearance of the tectal plate

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related to a more horizontal appearance

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and configuration of the inferior colliculi.

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Now,

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every patient with Chiari type II malformation

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is a little bit different.

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This patient,

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the corpus callosum, doesn't look too abnormal.

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We're seeing somewhat truncation of the

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rostrum of the corpus callosum,

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but the genu and the body of the

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corpus callosum are normal.

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We have the physiologic thinning of the isthmus,

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and we have the splenium of the corpus callosum.

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The corpus callosum may be slightly

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smaller than usual,

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but this is not as abnormal as we sometimes see.

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Here,

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we see what may be an interhypothalamic adhesion.

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This is a finding that has been seen slightly

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more commonly in the setting of a

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Chiari Type II malformation.

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Notice other adjacent structures.

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There's the massa intermedia.

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There is the anterior commissure,

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the optic chiasm.

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But this structure right here,

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just posterior to the lamina terminalis,

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might be an interhypothalamic adhesion.

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If we look on this Chiari type II malformation,

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we can see there's a ventriculoscopy catheter

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in place because there's a near 100% association

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of Chiari Type II malformation with hydrocephalus.

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Now, with the ventriculoscopy catheter in place,

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the ventricles are now normal in size,

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so it's doing its job.

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But we see another interesting finding that's

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characteristic of Chiari type II malformations.

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We see interdigitation of gyri

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across the interhemispheric fissure.

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This is felt to be related to fenestration

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of the falx cerebri.

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And in this case,

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you actually could even see this finding

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on this coronal head ultrasound

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at one month of life.

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So, we're seeing interdigitation of gyri in the

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setting of a Chiari Type II malformation with

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the characteristic posterior fossa and

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supratentorial abnormalities.