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So this patient presented with multiple

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cranial neuropathies on the left side,

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which included hearing loss but

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also difficulty swallowing,

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suggesting that there was a 9th and 10th nerve palsy

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as well. So let's take a look at the top left image.

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So this is the heavily T2-weighted image.

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And again,

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I'm going to draw my line down the middle.

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And again,

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one of the things that I always do on my head and

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neck case, I draw my line down the middle,

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and I compare one side to the opposite side.

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Now, this patient's symptoms were on the left side,

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so I'm really looking for pathology.

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So let's analyze this image.

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Heavily T2-weighted image

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has cranial neuropathies.

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So here's our Porus Acusticus

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on the uninvolved side.

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And now I can see this nerve

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here and this nerve here.

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And as I follow it through the Porus Acusticus,

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I can see nice, clear CSF.

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Now let's take a look on the symptomatic side,

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I can see this nerve, which is anteriorly,

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which is going into the cochlea.

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So that's a cochlear nerve.

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And if I'm at the level of the cochlear nerve,

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then I have to be at the level of

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the inferior vestibular nerve.

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So in the fungus of the internal auditory canal,

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I can see those two nerves.

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But as I extend more medially,

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all of a sudden I see this mass right here,

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which I cannot explain.

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It's too high to be the flocculus,

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and there should be nothing extending into

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the Porus Acusticus at this level.

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If I look at the lower image,

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this is a non-contrast T1-weighted image.

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Maybe with a leap of faith,

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I see a little bit of mass right here.

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It's hard to say, but when we give contrast,

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there's clearly a mass here that's involving

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the left cerebellopontine angle,

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but does not extend through the Porus Acusticus,

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nor does it have the dural tail.

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So this particular case,

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it doesn't have the dural tail.

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It's extending medial to the porus acusticus,

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so it's probably not a vestibular schwannoma.

1:54

So now I have to think,

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what are the things that could arise in the

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cerebellopontine angle that do not have a dural

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tail that are not extending into the internal

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auditory canal that are extra-axial?

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So I have to think of various things.

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So one of the things I look for when I'm looking at

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the CP angle or any mass that I'm not sure of is,

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are there multiple lesions? So at this level,

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we're at the level of the internal auditory canal.

2:21

Once we go lower into the midbrain, again,

2:24

I'm going to draw my line down the middle

2:26

and compare one side to the other side.

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The patient's symptoms run their left side.

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So when I start looking at the left side,

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I see these two little lines right here.

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And these two little lines correspond

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to the lines on the left side.

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And this is the 9th and 10th nerve complex extending

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into the jugular foramen. And just anterior medial,

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we can see this enhancing mass that

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is abutting these various nerves.

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So now I'm dealing with two lesions.

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And then if I look even a little bit closer,

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there's another area right here of enhancement.

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That's involving the leptomeninges of the medulla.

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So now, all of a sudden,

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I have three focal areas of enhancement.

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One at the level of the internal auditory canal,

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another one adjacent to the left

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9th and 10th nerve complex,

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and a third area of enhancement along the

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leptomeninges adjacent to the medulla.

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So when I have multiple enhancing lesions in the

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posterior fossa, the diagnosis is more than likely

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leptomeningeal metastases.