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This is an ultrasound of the head in a newborn infant

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that had an abnormal fetal ultrasound.

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The ultrasound was performed through

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the anterior fontanelle

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and this is in the coronal plane.

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We can see sulcation here in the location where

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you'd expect the anterior aspect

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of the interhemispheric fissure.

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You can actually see gray matter and

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sulcation going across the midline.

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And so, this is not normal.

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Normally,

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the two cerebral hemispheres do not have any

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sulcation that crosses over.

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At a later age,

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a CT scan of the head was performed.

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This shows an abnormal ventricular system.

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There's no septum pellucidum.

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The lateral ventricles posteriorly are larger

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than you would normally expect,

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and we're not seeing the anterior horns

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of the lateral ventricles very well.

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We're not seeing good delineation

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between the two thalami,

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and we're also seeing gray matter continuity

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across the expected location of the

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interhemispheric fissure, anteriorly.

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Now,

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posteriorly, we are seeing a falx cerebri.

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Anteriorly, we do not see a falx cerebri.

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So, this is an individual that has elements

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of a holoprosencephaly spectrum disorder.

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But posteriorly,

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we look like we have two different

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cerebral hemispheres,

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unlike the case of the alobar

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holoprosencephaly that we saw.

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But anteriorly,

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we're seeing signs of a single

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cerebral hemisphere.

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An MRI is performed showing some

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fusion of the thalami,

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which is a diencephalic structure and anterior

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midline continuity across the expected location

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of the interhemispheric fissure, anteriorly.

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This corresponds with the appearance

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on the ultrasound.

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We also see a single or azygous anterior cerebral

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artery right here.

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Posteriorly, we see a falx cerebri,

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and we see two separate occipital lobes.

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So, this patient has some features

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of holoprosencephaly,

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but it's not as severe as the alobar

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holoprosencephaly that we saw.

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If we look at this sagittal T1-weighted image,

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posteriorly, we see a normal-appearing

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cerebellar vermis,

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relatively normal-appearing brainstem.

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We can see normal sulcation in the precuneus of

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the parietal lobe, as well as in the occipital lobes.

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Here.

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We're seeing the posterior portion

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of the corpus callosum,

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the posterior body isthmus and splenium.

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Anteriorly, we lose the corpus callosum.

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Anteriorly, we also have,

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along the interhemispheric fissure,

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we have actual gray matter,

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where there normally should just be white matter.

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So this is a patient with,

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posteriorly, it looks like the two cerebral hemispheres

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separated from one another.

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Anteriorly, they did not.

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And this is a holoprosencephaly spectrum

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disorder referred to as semilobar

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holoprosencephaly.