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This is an MRI of the brain

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in a three-and-a half-year-old child

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with some vision abnormalities.

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One of the first things we notice is

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absence of the septum pellucidum.

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We see the two lateral ventricles

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are normal in size,

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but there's no intervening septal leaflets.

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As we scroll through the brain overall,

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sulcation pattern looks normal.

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The myelination pattern looks

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appropriate for age.

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So, other than the absence of

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the septum pellucidum,

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the brain itself looks fairly normal..

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If we go to the sagittal T1-weighted image

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and we zoom in on the supercellular region,

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we can see the optic chiasm is smaller

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than we typically expect.

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This is the pituitary infundibulum.

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Here's the adenohypophysis.

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This area of T1 shortening is the

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neurohypophysis.

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Mammillary bodies.

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Here's the third ventricle.

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We have the infundibular recess and the

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chiasmatic recess of the third ventricle.

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But the optic chiasm is smaller than

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it typically should be.

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Well, let's look at the optic nerves otherwise.

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So on this coronal image,

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we're going to zoom in, and we can see,

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we can barely see the optic nerves.

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The bright around it is CSF within

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the optic nerve sheath,

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and the optic nerves themselves are small.

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On this coronal image,

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we can see the optic nerves are small.

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We will zoom in,

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and we can see the optic nerves are small

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throughout their course in the orbit,

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going back here to the optic chiasm.

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That's the pituitary infundibulum coming

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down from there.

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So, we can follow the optic nerve bilaterally

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is small.

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And the axial image confirms,

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you should see a very thin optic nerve,

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which is the T2 hypointense structure within

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the central aspect of the optic nerve sheath.

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If you remember, the optic nerve is,

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truly speaking,

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a part of the central nervous system.

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It's surrounded by CSF and Dura.

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The dura is the optic nerve sheath.

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So, this patient has bilateral optic nerve hypoplasia.

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Also, hypoplasia of the optic chiasm

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and absence of the septum pellucidum.

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That spectrum of abnormalities is

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known as septooptic dysplasia.