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Hello, I'm Dave Yousem,

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and today I'm going to be talking to you about part

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two of the temporal bone, the middle ear.

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My objectives today are to identify the

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manifestations and complications of the various

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inflammatory diseases of the middle ear.

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And this is because, for the most part,

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we are asked as neuroradiologists to evaluate the

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middle ear in patients who have chronic otitis

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media. You'll see COM, for example,

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for chronic otitis media versus cholesteatoma,

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we'll also talk about the various vascular regions

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of the middle ear and how important it is to

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distinguish a glomus tumor from a normal vascular

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variant such as an aberrant internal carotid

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artery or a dehiscent jugular bulb.

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And then we'll also talk about some of the

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unusual lesions in the temporal bone,

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including the neoplastic lesions.

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And we'll finish with some trauma in the middle ear.

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The protocol that one uses for imaging in the

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middle ear is dominated by CT scanning.

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So we use MRI infrequently mainly as a problem

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solving technique. But CT really is the mainstay,

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and with CT, you're doing axial thin-section images.

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For most scanners,

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they're going to be less than one

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millimeter in thickness.

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We usually do them at 0.5 to 0.6 millimeters.

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And then we're going to have multiplanar

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reconstructions in coronal or sagittal or even

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radial images for when we're looking at

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superior semicircular canal dehiscence.

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The general CT scan is done without contrast.

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However, if there are vascular lesions that are suspected,

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contrast may be given in a situation

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very similar to CTA.

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And you may use dynamic imaging if you're trying to

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distinguish between a vascular tumor versus

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a neurinogenic tumor. For example, for MRI,

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we are using fast boneco diffusion-weighted imaging to

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distinguish cholesteatoma from chronic

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otitis media and thin-section images.

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With your skull-based protocol,

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we're using CIS images or Fiesta images with

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ultra-thin sections, as well as MP,

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Rage or Vibe images on the T1-weighted scan

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again if a vascular lesion is suspected,

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one might add MRA.

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So I want to review a little bit of the anatomy

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before we get to the first case,

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in which case we'll review anatomy on the CT scan.

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But I want to start with some diagrams.

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So these diagrams are nice illustrations that show

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the intricate anatomy of the middle ear cavity.

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And the middle ear cavity on these coronal images

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can be seen as that space which is

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medial to the tympanic membrane.

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So we have the external auditory canal going to the

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tympanic membrane, and then we have the space.

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Between the tympanic membrane and

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the inner ear structures,

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this being portion of the vestibule and the cochlea.

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So it's this space that houses, as you can see,

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several stabilizing ligaments as well

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as the middle ear ossicles,

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as well as some nerves that cross through

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and some muscles that cross through.

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And we'll describe those on the CT scan.

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As I mentioned,

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there are vascular structures which may course into

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the middle ear cavity when there are aberrancies and

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those include vascular structures from the internal

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carotid artery or the jugular bulb.

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As I mentioned,

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the main anatomic structures of the middle

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ear cavity are the middle ear ossicles,

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and this is a nice diagram from the people at MRI

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online demonstrating the malleus as well as

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the incus and the malleoincudal joint,

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and then the long process of the incus articulating

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with the capitulum of the stapes in the incudostapedial joint.

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The pedial joint.

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And then the stapes being seen here,

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fixating into the oval window.

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So with that diagrammatic anatomy we're going to now

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see a CT scan where we can see the anatomy

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as it is displayed on thin section CT.