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Endolymphatic sac tumors are sometimes

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abbreviated ELSTs.

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They were previously called papillary adenomas

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tumors because of their histologic similarity in

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some of the cellular features to

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a thyroid papillary carcinoma.

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But these are usually benign tumors that have

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a relatively aggressive appearance to them on CT scan,

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where you see irregular margination along the plane

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of the petrous portion of the temporal bone extending

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to the mastoid portion of the temporal bone.

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So these are associated with the endolymphatic sac

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and they are characteristic because they have high

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signal intensity on pre-gadolinium

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T1-weighted scans.

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And this is thought to be either due to a highly

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proteinaceous cystic material or hemorrhagic

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products on the T1-weighted MR,

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causing them to be bright in signal intensity.

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The lesion will generally enhance superimposed on

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that high signal intensity on the T1-weighted scan.

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And this is a lesion that is associated

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with von Hippel-Lindau disease.

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So I always teach people that when you're looking at

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patients who have cerebellar hemangioblastomas,

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always look at the temporal bone to see whether

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they have an endolymphatic sac tumor.

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And similarly,

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when you're looking at the temporal bone CT in

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a patient who has an endolymphatic sac tumor,

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look at the soft tissue windows and see whether you

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see any masses that are cystic or solid in the

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cerebellum which might indicate hemangioblastomas

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and the diagnosis of von Hippel-Lindau disease.

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How they look. So here is the CT scan.

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As you can see in this case to the right,

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this patient has a mass which was evident at

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otoscopy and was felt to represent a middle

1:53

ear cavity mass. In point of fact,

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the mass's center is really along the endolymphatic

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sacro vestibular aqueduct and it really grows in the

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plane of the petrous portion of

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the temporal bone seen here.

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So it's a destructive mass growing through the

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mastoid bone and into the tympanic cavity.

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This is a different patient taken from one of my

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textbooks, and you see that the mass has matrix,

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which is hyperdense calcified,

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almost bony matrix to this lesion,

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but it still has kind of that bubbly appearance

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that the other case had,

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which extends potentially into the middle

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ear cavity. On MRI scanning,

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this is the characteristic feature. You see on the

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pregad T1-weighted scan areas

2:45

of high signal intensity,

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either peripherally or centrally within the lesion.

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And that is unusual on this fatsat T1-weighted,

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in this case, coronal scan.

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What is the cause of the bright signal?

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Again, hemorrhagic products or hyperproteanaceous

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fluid within the mass.

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Here is the T2-weighted scan in the axial plane.

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You see that characteristic growth in the plane of

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the petrous portion of the temporal bone or the

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plane of the endolymphatic sac / vestibular aqueduct.

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Same thing.

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On the post-gadolinium T1-weighted scan,

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we see that the vast majority of this lesion

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is showing contrast enhancement.

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We have the superimposed bright signal

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intensity in the periphery,

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but there are portions that are

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showing contrast enhancement.

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So this combination of MRI findings

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is pathognomonic

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when you look at also the location of the

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lesion for an endolymphatic sac tumor.