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This is the first of a series of three lectures.

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I'd like to give on the temporal bone.

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Temporal bone classically is separated into

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the external auditory canal portion,

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the middle ear portion, and the inner ear portion.

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That said,

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there are numerous other portions of the temporal

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bone, including the squamosal portion,

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which makes up portions of the skull,

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the mastoid portion, the tympanic portion,

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which makes up the predominant part of the external

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auditory canal as well as the petrous portion.

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And in some cases,

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the petrous portion of the temporal bone talk

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is included in the skull-based talk.

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So we're going to start by working from outside in

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and that is with the external auditory canal and

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then move inward with a separate talk on the middle

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ear and a final talk on the inner ear.

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So let's start in with the external canal.

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For this talk, we'll initially go over the anatomy

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and for the sake of those individuals who are not

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as comfortable with temporal bone anatomy,

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I'm probably going to review the anatomy on all

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three talks of the external auditory canal,

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the middle ear, and the inner ear.

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Some of you will appreciate that,

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some of you can fast forward through it.

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So we'll talk about the generally deformed ear and

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then talk about inflammatory diseases of the

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external ear and then masses of

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the external auditory canal.

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For those of you who are familiar

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with my style of teaching,

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you know that I typically refer to the pathology

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in different areas of the neuroradiology world in

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terms of a mnemonic known as vitamin C and D,

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that is, vascular, infectious, traumatic, acquired,

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metabolic, idiopathic, neoplastic,

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congenital, and drugs with respect to

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external auditory canal disease.

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The vast majority of these are going to be

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inflammatory lesions, and then congenital lesions for

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which we evaluate. There are relatively few

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in the way of neoplasms that affect the

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external auditory canal.

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And trauma will lead to a facial bone trauma

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talk that will be given separately.

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Here is an anatomic drawing that was provided by

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Paul Bohart for our discussion of

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the external auditory canal. Now,

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when we talk about the external auditory canal,

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we're referring to this portion of the

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temporal bone and the anatomy.

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We don't really refer too much

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to the external ear portion.

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So we have the helix and the concha of the ear and

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these are areas where we will be talking about with

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respect to the malignancies that can

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affect the external canal.

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Most of the malignancies that affect the external

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auditory canal are in point of fact skin cancers.

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There can be tumors that are affecting the

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exposed portion of the external

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ear and then growing into the

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external auditory canal.

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So for now we're going to leave the helix in the

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external ear alone and refer to the anatomy

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of the external canal.

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As you can see by the anatomic drawing,

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there are two different portions that we usually

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refer to with regard to the external canal.

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The cartilaginous portion which is depicted by the

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greenish tissue here and here of the cartilage

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of the external auditory canal.

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And then you see the conversion to the bony external

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auditory canal which is seen leading

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to the tympanic membrane.

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The tympanic membrane is the border between external

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auditory canal and middle ear cavity.

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And then we have the inner ear structures

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deep to the stapes.

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So Paul has nicely shown the middle

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ear ossicles of the malleus,

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the incus and the stapes and then the inner ear

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structures dominated by the

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cochlea and the vestibule.

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There's one anatomic curiosity that I do want to

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highlight on the diagram that is well depicted and

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that is the junction between the cartilaginous and

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the bony portion of the external canal.

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And at this junction we have something called the

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fissures of Santorini. I love saying that.

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The fissures of Santorini I'll be describing as

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the source of the infection of the skull base.

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That is apparent in patients who

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have malignant otitis externa.

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Malignant otitis externa is fulminant infection with

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Pseudomonas that goes from the external auditory

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canal to the skull base and usually causes an

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element of osteomyelitis and cellulitis.