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You know it's funny, as physicians,

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sometimes we have favorite lesions,

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and the endolymphatic sac tumor

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is one of my favorite lesions.

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Some of you may recall in the spine talk about

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how I love, you know, intradural extramedullary tumors,

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largely because they're mostly benign.

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But the endolymphatic sac tumor is kind of a quirky

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lesion that is somewhere between a benign and a

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malignant tumor. In that it is aggressive

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and leads to bone destruction,

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but it does not have metastatic potential.

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So it's kind of an unusual lesion.

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And one of the other unusual facets of it is that it

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may be seen in association with the

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phakomatosis of Von Hippel-Lindau disease,

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which is what we're labeling here, V-H-L.

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These patients do tend to

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present with hearing loss,

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and it is a lesion that may affect the petrous

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apex and the inner ear structure.

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When it occurs with Von Hippel-Lindau disease,

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you may see it bilaterally. If you're looking at the

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patient because of hearing loss and you see this

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lesion of the petrous bone that is destructive,

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and on the MRI,

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you also see a mass that's enhancing

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in the cerebellum,

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then you'd have the great combination to suggest

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hemangioblastomas with endolymphatic sac tumor and

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a new diagnosis of Von Hippel-Lindau disease.

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Here is the lesion on CT.

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It typically has a lytic component.

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It's oriented sort of in the

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plane of the petrous bone,

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and it may have some matrix associated with it.

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Here's another example of a patient who

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has an endolymphatic sac tumor.

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You notice again that by and large,

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it's oriented along the plane of the petrous bone.

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Here's the petrous apex.

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But in this case,

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it has grown into the middle ear cavity and may be

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presenting as a mass over the cochlear

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promontory with hearing loss.

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There's a broad differential diagnosis that this

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could be including potentially a metastasis or even

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a spread from something like

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a nasopharyngeal carcinoma.

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So this is a tumor that has previously been called

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the papillary adenomas tumor. In fact,

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initially some people thought that this represented

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a thyroid metastasis to the petrous apex,

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but then it was discovered that it was

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a unique tumor in and of itself.

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It has irregular margins, calcified matrix.

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And the fascinating part on MRI scan is that it's

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a lesion that has high signal intensity on T1-weighted scan

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by virtue of either hemorrhage or the

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intratumoral matrix bone of it that it creates.

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It is a tumor that will show contrast enhancement.

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But this is kind of an Aunt Minnie.

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When you see one of these,

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you'll make the diagnosis forever.

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And here it is.

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This is a coronal T1 fat sat scan.

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And what one sees are these little locules of

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bright signal intensity in this expansile

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petrous apex mass, and

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this bright signal intensity, with little foci with

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heterogeneous signal intensity is stereotypical

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of an endolymphatic sac tumor.

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Here it is on T2-weighted scan which typically

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shows heterogeneity. But again, oriented

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in the plane of the petrous apex.

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Here it is post-gadolinium,

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where you see on the coronal scan

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the enhancement of the lesion.

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So it has bright signal intensity pre-gad in little

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tiny locules, often in the periphery.

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But on post-gad,

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you see that the tumor shows enhancement.