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Well, welcome to my first case review live.

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As Ashley mentioned, I'm Kristen Bonio. I'm a head and neck neuroradiologist

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from Emory University down here in Atlanta, Georgia. Hopefully, today I'm

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going to review some interesting head and neck cases with you.

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As she mentioned, I have nothing to disclose.

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Hopefully, we'll get through as many cases and questions as possible.

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My goal here is to really review as many interesting and high yield

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head and neck cases as possible. We're going to go through at least

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seven unknown cases, but I'll have lots of companion cases to show you.

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Hopefully, we'll look at a lot of different pathology.

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Starting with case 1. We're going to start with everyone's favorite,

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the skull base. I'm going to show you some scrolling images of a

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25 year old patient with a headache. Here is this patient's CAT scan.

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You can see here, if you go up and down, that there's a

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lesion in the skull base. This portion of the skull base is called

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the petrous apex. It's the petrous portion of the temporal bone right before

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it joins the petroclival synchondrosis with the clivus. You can see there's

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this lucent lesion. Over here, you have pneumatized air cells in the petrous

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apex. There's this large expanse of lucent lesion causing mass effect and

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a dehiscence involving the carotid canal on the right. But it's fairly well

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circumscribed with fairly clean edges, this lytic lesion. We saw this lesion.

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The next step is to recommend an MRI

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to further characterize this lesion. Any lesion of the skull base, especially

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the petrous apex, a CT and MRI is a complimentary. Here's this patient's

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MRI. We started out with the flare images here. You can see

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nothing really going on in the brain, but there's this very bright,

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very T2 hyper intense lesion in the right petrous portion of the temporal

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bone. It's very bright on T2 and you can actually see there's a

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little fluid fluid level within this lesion with a little bit of layering

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T2, relatively hypo intense soft tissue. You can also see that on the

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CISS sequences. We did some very thin section, heavily T2 weighted images,

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CISS or Fiesta sequence. Here you can again see this very large complex

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cystic lesion, causing mass effect on the carotid artery with some areas

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of layering T2 heterogeneity. Then we have the T1 pre and post contrast

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images. Here on the pre contrast images, you can see it's very very

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uniformly bright on T1 weighted images. Then on the post contrast images,

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you can see that there's just a thin rim of peripheral enhancement.

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Sometimes it can be hard to tell if these things are enhancing when

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there's so much intrinsic T1 hyperintensity. But this one, you can just

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see that there's just a tiny bit of thin peripheral enhancement around the

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lesion. Returning back to our PowerPoint. Some of the salient imaging findings

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in this case, again, we have this lytic expansile, well circumscribed lesion

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on CT, which is hyper intense on the T1 weighted pre contrast images,

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also hyper intense on T2 weighted images with a fluid fluid level,

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but no real enhancement except for maybe some thin peripheral enhancement.

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That leads us to our first poll question.

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What's the most likely diagnosis of this right petrous apex mass? Is it

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just asymmetric marrow in the petrous apex, trapped fluid,

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a cholesterol granuloma, chondrosarcoma, or petrous apicitis? So here's

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our poll. Let's see what you all said. Give you a minute

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to answer. Okay, what do you think? Can you show me the answer?

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Good, 100%. Awesome. You guys are awesome, that's correct. I'm going to

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close this. Yes, this is, oops, a cholesterol granuloma. A Pretty straightforward

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case. We're going to start with the easier cases and move on to

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some harder ones. Cholesterol granuloma is the most common primary lesion

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of the petrous apex. It occurs as a result of bleeding into pneumatized

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air cells. Sometimes there are two theories as to how these develop. It

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can be a result of chronic obstruction or bleeding into hyperplastic mucosa

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within the obstructed cell. The blood products become trapped and break

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down into cholesterol crystals, hence the name cholesterol granuloma, and

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they can incite a sterile local inflammatory reaction.

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This can often lead to incidental and asymptomatic cholesterol granulomas

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to become symptomatic once these patients bleed into them and cause this

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inflammatory reaction. The symptoms can range from headache to other symptoms

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that result as a mass effect on the cranial nerves such as hearing

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loss, tinnitus, vertigo, or even facial twitching. On CT again, they're

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well defined and expansile. As in this companion cases, in another case

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of the left, petrous apex, cholesterol granuloma. You can see on the T1

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weighted images, it's bright, but on the T2, you might think it's just

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some trapped secretions in the petrous air cells. Because it still maybe

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looks like there's some septations, but on CT, you can see there are

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definitely no septations, and it's definitely well defined and expansile.

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This is compatible with cholesterol granuloma. These are often treated with

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mass reductomy and decompression as they can continue to enlarge and cause

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compressive symptoms. Just to take you through some of the differentials,

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some of the other petrous apex pathology. Occasionally, asymmetric marrow

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in the petrous apex can be confusing and sometimes presented as a pseudolesion,

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especially if you're only looking at your T1 weighted images,

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or on your T1 weighted post contrast images without fat saturation,

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you may think you're seeing an enhancing lesion.

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But just looking at all of the other sequences will show that it

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follows fat. And this is just asymmetric pneumatization of the skull base.

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It's pneumatized on the left and not on the right, so this is

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just marrow, and it follows marrow on all the sequences including CT.

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Again, CT is often very complimentary on anything that you think is a

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little funky in the skull base. Always consider getting a CT if you're

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looking on MRI. Here are all those imaging findings I talked about.

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Trapped fluid in the petrous apex is another lesion that can mimic cholesterol

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granuloma. This is a normal variant. It should not be pathologic.

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It's essentially a pseudolesion due to fluid that's retained in some petrous

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air cells. It should be very hyper intense on T2. And the key

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to making this diagnosis is seeing the retained septations of the air cells.

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But again, if you're not sure about it,

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you want to get, and these can also be variable signal on T1

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weighted images because you can occasionally get trapped fluid that becomes

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protonaceous and inspissated. It can get a little bit bright on T1 and

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can mimic a cholesterol granuloma. But on CT,

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if you see retained septations within the petrous apex air cells and a

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non expansile lesion, then you're just dealing with trapped fluid. Contrasarcomas,

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again, another lesion that can occur in this location, in the petrous apex,

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and can mimic a cholesterol granuloma. These are lesions that occur most

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frequently centered around the petroclival synchondrosis. They're lytic

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and lucent on CT, often with a narrow zone of transition,

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similar to our initial lesions, sort of well circumscribed.

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But they can also have chondroid matrix in up to 50%

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of cases. They are very characteristically, very hyper intense on T2 weighted

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images. You can see it's just about as bright as CSF here.

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They can have lobulated margins. This is similar to chordoma, which is also

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in the differential of these skull based chondrosarcs. They're variably

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enhancing, as in this case, of an avidly enhancing chondrosarc. But one

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way you differentiate from cholesterol granulomas, again, looking at the

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pre contrast T1 weighted images, and chondrosarcs definitely are not uniformly

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bright on T1. They may have some areas of mineralization and intrinsic T1

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hyper intensity but should not be uniformly bright.

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Another example of a chondrosarcoma, the more typical and classic chondroid

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matrix with those arcs and rings you can see.

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Again, centered in the region of the petroclival synchondrosis, eccentric

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in the region of the clivus and the petrous apex. The more characteristic

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heterogeneous and variable enhancement pattern. Then finally, the last example

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of a petrous apex pathology is petrous apicitis. This really presents in

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a very different fashion. These patients are really sick, they present with

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an acute infection. Usually, it's contiguous extension of an otomastoiditis,

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as in this case, but you can also rarely get a hematogenous extension.

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It's essentially a skull based osteomyelitis, and patients are usually pretty

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symptomatic. Fever, elevated white count, they usually have otalgia and

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facial pain. The classic clinical triad is gratiningo syndrome, where you

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can see symptoms of acute mastoiditis, as well as deep facial pain,

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and occasionally a lateral rectus or cranial nerve six palsy.

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Because remember, cranial nerve six does extend through

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the durello's canal, which goes through the petrous portion of the temporal

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bone. Often on CT, you can see this expansile soft tissue in the

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petrous apex, but often associated with some trabecular breakthrough, the

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breakdown and the septations and on areas of cortical dehiscence and erosion.

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Then obviously, if you see anything like this, you're going to recommend

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an MRI. Anytime you see any bony dehiscence of the skull base, you

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really should look on MRI. Again, any skull based pathology, CT and MRI

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are complimentary. In this case, you want to do an MRI to assess

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for intracranial extension, which you often have in these cases,

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as in this patient where you can see this

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peripheral enhancing soft tissue in the petrous apex, but also extensive

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enhancement, and of course, in the mastoids, and then extensive enhancement

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of the surrounding marrow, and then adjacent neural enhancement and thickening.

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The patient also had some meningeal signs. You can also get associated vasospasm

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at the adjacent carotid and arteritis. These patients are typically treated

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with broad spectrum antibiotics, but often mastoidectomy and surgical drainage

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is needed as well. In summary, cholesterol granuloma limit can mimic an

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enhancing lesion, so you really need to make sure you look at your

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T1 weighted pre contrast images, and for any petrous apex lesion, MRI and

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CT can be complimentary.