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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.