Interactive Transcript
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This is a 16-year-old child
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who was in a car accident, hit their head,
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and a head CT was performed to look for signs of
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intracranial traumatic injury.
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Fortunately,
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there were no signs of traumatic injury.
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No fractures, no bleeding or anything like that.
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But one thing that caught people's attention was
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this cystic appearing area here does not
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look like an acute traumatic etiology,
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but it definitely was puzzling,
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and it resulted in a brain MRI being performed.
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An MRI of the brain was performed and shows a
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normal development of the cerebellar vermis.
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We see the superior medullary velum,
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the inferior medullary velum,
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that little angle where they come together
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is called the fastigium,
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and there's a normal fastigial angle.
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Overall,
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the cerebellar vermis looks on this mid-sagittal
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image, like the video game character Pac-Man,
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directed towards the brainstem.
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So the cerebellar vermis is normal,
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but there is prominence of CSF posterior
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to the cerebellar vermis.
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It's pushing slightly to the right,
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the falx cerebelli.
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This is demonstrating hyperintense
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signal on T2-weighted imaging.
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It suppresses on FLAIR imaging.
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It's hypointense on T1-weighted imaging,
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and it demonstrates facilitated diffusion.
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All of those other features help us know
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that this is just an arachnoid cyst.
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It's an arachnoid cyst behind
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the cerebellar vermis.
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So, it's known as a retrovermian arachnoid cyst.
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This is normal.
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This is not a Dandy-Walker spectrum malformation.
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This does not require imaging follow-up.
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This does not require neurosurgical consultation.
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This does not require consternation
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on the part of the clinical team.
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This does not require anxiety on the part of the patient.
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This is a normal finding.
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Now, notice this retrovermian arachnoid cyst results
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in slight elevation of the torcula.
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So, the position of the torcula alone actually is
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not a feature to diagnose
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or exclude a Dandy-Walker spectrum malformation.
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This patient does not have a Dandy
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Walker spectrum malformation.
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This patient does not have any
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pathologic abnormality.
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They have a retrovermian arachnoid cyst,
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which is a normal variant.
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