Interactive Transcript
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This is a CT scan of the head
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in a twelve-year-old female,
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and this is performed for headaches.
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In the process, we're looking.
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We're seeing an upper normal caliber of
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the lateral and third ventricles.
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We're seeing the fourth ventricles,
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normal in size.
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Otherwise,
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everything so far is looking normal.
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But it's always important to pay attention
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to the level of the foramen magnum.
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And we're seeing here,
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we're seeing the brainstem,
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and we're seeing the cerebellar tonsils.
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And
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a little bit of visualization of the cerebellar
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tonsils at this level can be okay,
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but we need to make sure that there's not
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something more going on.
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Fortunately,
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modern CAT scans have the ability for
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multiplanar reformats.
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And this image here,
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if we look closely, we actually can't really
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delineate where the cerebellar tonsils end.
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And it's very tight at the level
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of the foramen magnum,
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there's a paucity of cerebrospinal fluid.
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And if we look at the bone algorithm data,
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we can see there's somewhat of a
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retroflexed odontoid process.
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A retroflexed odontoid process is commonly
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associated with a Chiari Type I malformation,
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and an MRI of
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the brain was performed.
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And again,
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while there's a little bit of motion artifact,
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we can still get a very good idea
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of what may be going on.
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This is the basion,
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the inferior aspect of the basiocciput,
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a part of the clivus representing the anterior
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margin of the foramen magnum.
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This is the opisthion,
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another part of the occipital bone that
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represents the posterior margin
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of the foramen magnum.
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If we draw a line between the basion
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and the opisthion,
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we can measure how far caudal there's
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cerebellar tonsillar ectopia.
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Now, that's a little tricky
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because everything is so tight,
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there's so little CSF.
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It's difficult to delineate what is brainstem
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and what is cervical cord
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and what is cerebellar tonsils.
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But the cerebellar tonsils extend at least
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15 mm below the foramen magnum,
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potentially up to 22 mm.
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So,
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in addition to that,
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we can see there's a paucity
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of cerebrospinal fluid.
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If we look closer at the rest of this image,
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we can see syringohydromyelia in
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the mid to lower cervical cord,
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extending below the field of view
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into the thoracic cord.
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So, we already know this patient has failed
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a physiologic CSF flow study.
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The next thing to be done is a posterior
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fossa decompression.
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If we look here, this is after decompression.
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We can see there has been resection of the
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inferior aspect of the occipital bone,
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opening up the posterior margin
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of the foramen magnum.
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So, we now have a widely patent
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neoforamen magnum.
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They often will resect the inferior-most
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portion of the cerebellar tonsils,
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especially in a severe case like this.
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For two reasons.
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Number one,
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in a severe case like this,
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the cerebellar tonsils are at risk of
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obstructing even the neoforamen magnum
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after decompression.
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Additionally, the cerebellar tonsils,
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the tips of them,
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often are atretic and damaged from
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being pinched for so long.
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So, this is a bony decompression.
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If the neurosurgeon feels like
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they need even more space,
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they can do a duroplasty to also
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open up the CSF space here
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to widen the dural space.
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This shows a successful bony decompression,
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but we can still see portions
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of the syringohydromyelia.
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But
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six months later,
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the syringohydromyelia has gone,
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has resolved.
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So the bony decompression without the duroplasty
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was successful in relieving the syringohydromyelia.
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And equally, if not more importantly,
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the patient's symptoms have resolved.
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