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This is an MRI of a six-year-old

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child with developmental delay.

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One of the first things we see on this

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mid sagittal T1 weighted image,

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is there's a dysplastic appearance

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of the corpus callosum.

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The corpus callosum is foreshortened

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in the AP dimension.

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We see the splenium of the corpus callosum,

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the isthmus, the body, the genu,

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and the rostrum.

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We see what looks like all the parts of it,

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but it's just smaller than we normally expect.

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The splenium of the corpus callosum

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should normally go posteriorly,

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to be posterior and superior to

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the pineal gland right here.

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The anterior commissure is

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also small in caliber.

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If we look on the axial T2-weighted image,

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we see an irregular configuration of the

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lateral ventricles.

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Additionally,

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on the lateral margin of the body

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of the left lateral ventricle,

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we're seeing some areas of irregular gray matter.

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So, this is gray matter heterotopia.

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So, this is a patient that has dysgenesis of the

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corpus callosum with gray matter heterotopia

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and an abnormal configuration of the ventricular system.

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Now, this patient also had seizures.

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And one of the treatments for seizures,

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in particular seizures with drop attacks,

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where a patient may fall,

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is transection of the corpus callosum.

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So, two years later,

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this is a mid-sagittal T1-weighted image

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after there was surgical transection of the

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corpus callosum.

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You can see on the axial image,

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this is in the early postoperative period,

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and we can see they've transected the fibers

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that were once crossing the midline

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in the corpus callosum.

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What this allows in a patient with what's called

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a drop attack, or when they have a seizure,

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they fall over.

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This prevents propagation of the seizure to

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the contralateral cerebral hemisphere,

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in which case the patient,

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when they have the episode,

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they do not lose full control of their body.

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Half of their body maintains control.

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So instead of falling over,

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they still have the ability to maintain

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some balance and catch themselves.

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One of the things postoperatively we may do

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is look at DTI imaging.

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In particular,

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this is the directionally encoded

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fractional anisotropy map.

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Red is the color of transversely

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oriented fibers.

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And we can see there's transection of the

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transversely oriented fibers in what previously

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was the rudimentary corpus callosum

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in this individual.

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We can also process that as diffusion

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tensor fiber tracking.

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And we can see these fibers go up to the

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transected margin of the corpus callosum,

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but they don't cross over.

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Similar, if we do a seed

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in the contralateral cerebral hemisphere

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and we can check different white matter bundles

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in different portions of the brain.

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And here, we do not see any fibers

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crossing the corpus callosum.

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These images with the diffusion tensor fiber

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tracking are one way to show the epilepsy

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neurologist and the neurosurgeon postoperatively

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that there has been complete transection of the

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commissural fibers traversing the midline

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in the corpus callosum.