Interactive Transcript
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This is an MRI of the brain
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in a six-year-old child with seizures,
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that at an outside institution
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was referred to as a Dandy-Walker variant.
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Now, if we look,
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we see the normal development
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of the cerebellar vermis,
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and that normal development of
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the cerebellar vermis tells us
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that this is not a Dandy-Walker
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spectrum malformation.
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There is no hypoplasia or
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intrinsic developmental abnormality
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within the cerebellar vermis.
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Now, there is prominence of CSF
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posterior and inferior to
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the cerebellar vermis.
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And if we look on this axial image,
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this CSF prominence is on both
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sides of the falx cerebelli,
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and it goes behind both
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cerebellar hemispheres.
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It's hyperintense on T2-weighted imaging,
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suppresses on FLAIR imaging,
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and demonstrates facilitated diffusion.
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So, this is an arachnoid cyst.
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There is no significant mass
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effect upon the cerebellum.
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I think this more likely is,
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given the absence of contra abnormality,
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just chronic remodeling and
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chronic slight expansion of the
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posterior cranial fossa.
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We also see chronic elevation of
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the torcula and the superior
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angulation of the posterior
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aspect of the straight sinus
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related to this.
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So, this is a retrovermian arachnoid cyst
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that's also infravermian.
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But there is no Dandy-Walker spectrum malformation.
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So, that's very important
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that there is not a malformation.
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Now, we do see CSF slightly prominent
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in the folia of both cerebellar hemispheres.
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And in a child with chronic anti-epileptic medications,
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you sometimes can see that.
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But that's not an intrinsic
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developmental abnormality.
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So, this patient does not have
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an intrinsic developmental abnormality.
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Therefore, there's no need to do a genetic
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workup for a cerebellar malformation.
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This is a retrovermian and
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infravermian arachnoid cyst.
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