Interactive Transcript
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This was a scan of a child that was being
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evaluated for recurrence of medulloblastoma.
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On the T1-weighted scan,
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before contrast,
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we note that the signal intensity of the
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vertebral body is just a little bit more
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bright on the T1-weighted scan
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than one would expect.
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This is yellow fatty marrow replacement for
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from radiation therapy.
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I noticed that also that the skull base,
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the patient has had surgery for the
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medulloblastoma. But even on the T1-weighted
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scan, if we just magnify a little bit,
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we see in the thoracic region that there are
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these areas of nodularity on the surface of
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the spinal cord with some widening of the
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subarachnoid space. As I mentioned,
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for subarachnoid seeding, really,
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we need post-gadolinium-enhanced scans,
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the T1-weighted and T2-weighted scans,
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unless it's pretty gross
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disease like this, are often negative.
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So when go to the post-gadolinium-enhanced images,
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you can see very thick contrast enhancement on
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the posterior portion surface of the spinal
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cord, indicative of subarachnoid seeding.
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There are some areas also on the anterior
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aspect at the C6 level.
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So I went back to look at the prior studies on
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this patient to see where the subarachnoid
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seeding was in the past that they were looking for.
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So if we go back to the patient's earliest
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most study and just pull up some
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representative images, pre and post-contrast.
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This is the flare scan.
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We see this large infiltrative
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mass in the posterior fossa,
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predominantly in the midline,
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but extending to the right side.
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And it just looks kind of aggressive the way
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it has enhancing areas, as well as non
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enhancing areas, but just sort of
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infiltrating the fourth ventricle
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and leading to hydrocephalus.
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So medulloblastomas are grade four,
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the most malignant of the brain tumors.
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Usually on the ADC maps,
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they're going to be dark in signal intensity.
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So this is diffusion-weighted scan.
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I'll bring up the diffusion-weighted image.
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So bright on the diffusion-weighted image,
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but dark signal intensity on the ADC map,
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reflecting low ADC,
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which is usually a marker of hypercellularity.
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And this is very typical of a medulloblastoma
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in the posterior fossa. On this scan,
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the patient did have surveillance for
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subarachnoid seeding, and on the post
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gadolinium-enhanced scans, while you see some
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of the enhancement of the
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posterior fossa mass,
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the scans through the spinal cord looked
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pretty normal. However, the CSF was positive.
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So this is an example of a patient
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who had medullobastoma,
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who had a relatively negative cord
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evaluation, pre and post-contrast,
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but had positive CSF in there.
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And then in follow up, and again,
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the follow up that I was looking at was four
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years after the initial resection of the tumor,
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had all of this bad subarachnoid seeding.
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Just to make the point on the examination of
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the brain, the only area of concern on the study.
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It looks like they got the primary tumor pretty well,
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except there was this one small area of
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enhancement which could represent subarachnoid
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seeding of the ependymal surface of the
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fourth ventricle, and then an additional seed
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at the interpeduncular cistern of the midbrain.
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So in this case,
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the primary tumor was taken care of,
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but unfortunately,
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the subarachnoid bread of the tumor was what
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was the main issue in four year follow up.
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