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Dr. P here.

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3 00:00:01,569 --> 00:00:05,980 This is a 35-year-old man who was diagnosed

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prospectively as having a ganglion

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pseudocyst as there was a palpable mass

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on physical examination in the office.

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Here's a coronal T2 spin echo image, and there's

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this funny-looking oval mass between M2 and M3.

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It's got quite a bit of

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heterogeneous signal inside.

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In fact, There's a duck inside there.

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See, there's the snout of the duck, there's

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the head of the duck, there's a wing, there's

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a wing, and there's the body, and maybe there's

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the tail right there, if you like to imagine.

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And the differential diagnosis here would

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include things like Morton's neuroma, a bursitis,

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a primary neural tumor, a vascular lesion.

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You have to think about things

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that live in this space.

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One thing that goes heavily against

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Morton's neuroma is the very

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aggregated appearance of water

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throughout the lesion.

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Even though there's quite a bit of debris and

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heterogeneous signal inside on a T2 Spin Echo

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without fat suppression, you should see more

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of a fibrous type of signal which is more

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intermediate in character, closer to muscle,

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a little lower in signal intensity than muscle.

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It's very encapsulated, by the way, and it

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squishes itself both towards the plantar aspect

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and the dorsal aspect of the foot. There is a fair

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amount of muscular atrophy throughout the foot.

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And now let's call up three sagittals,

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see if we can get it to behave.

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Here we go, here's a sagittal PD fat sat.

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Here's another PD fat sat, and here's a T1 spin echo.

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And I don't know why we have two PD

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fat sats here, but nevertheless,

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the lesion is a little bit exophytic,

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it has some very strange signals inside.

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Some are low, but these little

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speckled signals are interesting.

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Especially right here in the T1-weighted image.

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They're high in signal intensity.

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There's not a lot of things that do that.

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Right?

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I mean, fat would be one thing.

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Blood, but speckly blood, that would be a bit odd.

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Small, osseous fragments containing marrow.

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That could do it as well, although

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that would also be a little bit weird.

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So, you might want to think about fat

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accumulating within this thing, some form of,

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say, fatty metaplasia, lipoma arborescens,

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which can occur in any synovial-lined object.

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So we scroll about a little bit, and once

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again we see that this thing does prolapse

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towards the plantar aspect of the foot,

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but it's mostly palpable dorsally, and you can

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see why the clinician thought this might be a

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ganglion pseudocyst, not unreasonable at all.

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Let's pull down the short-axis projections.

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We've got a short-axis T1, a short-axis simple

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T2 without fat suppression, and then on the right,

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we've got a proton density fat suppression image.

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There again are heterogeneous areas of signal

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alteration throughout with some high signal

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T1, so several things come to mind here.

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First of all, the disorganization of the

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internal signals goes against a neural tumor.

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I mean usually when you're dealing with a

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schwannoma, they're either completely cystic and

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homogeneous, or they have this sort of pointillism

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effect where the nerve cells are coming at you.

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So they're a little bit more organized,

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and it's a very weird, odd place for a schwannoma.

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A neurofibroma, not always, but it tends to have

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something that looks a little bit like this.

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In the middle, you'll often see a little

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sort of fibrous, almost a triangle or a

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star in the middle, and then you may get

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some even radiating linear signals,

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fibrous signals coming out of it.

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And neurofibromas tend to be more

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fibrous-like than, say, the schwannoma,

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which may be a little more cystic-like.

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I know many of you know that neurofibromas

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arise directly from the nerve.

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So they are important to differentiate from

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schwannomas because neurofibromas don't peel out.

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Usually, you have to sacrifice the nerve,

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whereas schwannomas, you can sort of peel

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them out like the rim of a baked potato,

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and then you leave the center of the

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baked potato, which is the nerve intact.

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So they have a much better

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prognosis when they're isolated.

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Then you get to the Morton's neuroma, and as

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stated, there's just too much high signal

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for that diagnosis.

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Now maybe you have a little bit of

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perineurofibrosis that's weaved

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in there, like this area right here.

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That's more fibrous and dark and signal intensity.

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But this area up here is very atypical for

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Morton's neuroma and much more typical

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for a bursal cyst, and within that bursal cyst,

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you can get, if it has synovium associated

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with it, various forms of metaplasia.

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You can get chondral metaplasia,

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you can get ossification of the chondral

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metaplasia, so you can get ossific signal.

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You can get lipoma, arboretions, you can

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get synovial chondromatosis, and so on.

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And you can also get just simple,

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or complex, synovitis within the lesion.

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And that's what's happening here.

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You're getting some synovitis,

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some metaplasia in this bursal cyst

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between the metatarsal heads M2 and M3.

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Now, one closing remark

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about bursitis lesions here.

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Unlike, say, Morton's neuromas, where we tend

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to be more conservative, we may inject them,

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sometimes you can release the transverse

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ligaments, occasionally you resect them,

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but as you know from spine imaging, you take out

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perineural fibrous tissue or a scar, what happens?

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You get more scar.

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So, these are easier to deal with.

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You can excise them.

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You can aspirate them.

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You can inject them.

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There's all kinds of options available to you.

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The prognosis is good.

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The diagnosis is bursal cyst between M2 and M3.

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Dr. P out.