 For each of the cases that I'm going to show in this temporal bone series I'd like to spend a little bit of time at the beginning Reviewing the anatomy because the more you go through it the better off you are in learning the anatomy and recognizing the various structures So we'll start with this first case, which was a patient who actually had hearing loss on the right side But we're going to look at the left temporal bone in the axial plane Now the scanning plane for the external auditory canal is important. It shouldn't be done straight transaxial Some of the cases that we do at Johns Hopkins are scanned straight transaxial with 0.6 to 0.75 millimeter thick slices, so that way we can Reconstruct it in any plane we wish to but we're just going to go with the anatomy as it was scanned Originally, so here we are looking at the external auditory canal and what we see are the structures of the external ear and You know the helix of the ear this is the external ear when we have a small external ear on a congenital basis the term that we usually use is Microsia and that may or may not be associated with external auditory canal atresia But this looks like a normal cartilaginous and soft tissue of the external ear Going in in this direction, we come to the external auditory canal And as we described in the original anatomy PowerPoint, we have two parts of the external auditory canal We usually refer to the cartilaginous part and then the bony part of the external auditory canal And we'll be seeing this obliquely on the axial scans at the level that we're looking at the external auditory canal We identify the mandible and we're going to be seeing the temporal mandibular joint shortly And we have some of the mastoid air cells. We have a little bit of the jugular frame and over here Let's continue to Scroll and as we scroll we see a greater portion of the bony portion of the external auditory canal Here diet you see the bone the interior wall and the posterior wall of the external auditory canal We are no longer seeing the cartilaginous portion We are just seeing the bony portion Where does the external auditory canal and it ends on this structure, which is our tympanic membrane So depending upon how you window the case you will see the tympanic membrane a little bit better or worse And as you can see I can sort of make the tympanic membrane go away completely versus Highlight it as you move more towards a air window a lung window if you will so part of Reviewing of the external auditory canal and temporal bone Anatomy is scrolling back and forth as well as changing the window and level of the CT scan So the tympanic membrane is Identified as the medial most portion of the external auditory canal So the pathology is going to be in the cartilaginous and bony portion and the adjacent soft tissues now that said There's often a lot of pathology that will extend from the external auditory canal Potentially through the tympanic membrane and into the middle ear so here we find the middle ear ossicles And I'm just going to move this a little bit more centered There we go and Let's identify the anatomy the most anterior of the middle ear ossicles is the Malleus and The one that is usually seen at the same level as the Malleus is the Incas and We usually identify the anatomy in terms of the ice cream and the ice cream cone With this being the head of the Malleus and this being the short process of them of the Incas So you're seeing a little bit of the ice cream and a little bit of the ice cream cone in this anatomy of the middle ear ossicles This is the middle ear cavity and when you have this little waist here that expands into the mastoid air cells This area of the waist is called the Adidas Adantrum and I'm not sure how many D's there are in Adidas, but Close enough. Adidas at the antrum is the connection from the middle ear cavity into the mastoid Air cells and the mastoid antrum so the Adidas referring to the middle ear cavity the antrum referring to the Mastoid air cells and the connection between the two many people have referred to this as kind of the the women's Not the best example of a woman's body, but the women's waist of Of the Adidas at antrum In addition, you're seeing a small soft tissue structure Which is heading towards the head of the Malleus and that soft tissue structure is the tensor timpani muscle So there are two main muscles in the middle ear cavity The largest one is the tensor timpani muscle going from the cochlear form process Which is this little bone prominence here to the? Head and neck of the Malleus and the other one is the stapedius muscle the stapedius muscle goes from the pyramidal eminence to the stapes and That is very rarely seen even on high-resolution CT, but we'll see how we do on this particular case on this same Section we are identifying the internal auditory canal. You have the widening of the cochlear aperture and You're seeing portions of the cochlea. This is probably the maybe a portion of the Basal or middle turn and then the apical turn of the cochlea You're also identifying the vestibule and some of the semi-circular canals, but they'll be more apparent when subsequent slices So as we go further inferiorly, I Want to point out this section So in this section we see two dots The first dot is the neck of the Malleus and The second dot is the long process of the Incas So we saw with the ice cream cone the short process of the Incas This is the long process of the Incas and you should see these two dots on every case If you're not seeing them then there's congenital absence of the middle ear ossicles potentially. As we continue downward I'm going to change the window just a little bit because what we're trying to identify is the Incadose the pedial joint and in point of fact you're seeing this on this slice. On this slice We have a little remnant of the Malleus neck You have a little remnant of the long process of the Incas and you see that there is a little joint right there Between something that looks kind of like that and something that looks kind of like that and What you're seeing is the long process of the Incas and one of the cura of the stapes and the communication here with what is again I'll be challenged on my spelling here the capitellum of the stapes Which is the portion that will articulate with the long process of the Incas So that's the anatomy that you're seeing You know on this scan. We're also seeing the vestibule. We're seeing part of the probably posterior Semi-circular canal just a little bit of the basal turn of the cochlea. I made this kind of bright and with long window Justice so that way we could see the portions of the stapes a little bit better Again, here you're seeing a portion of the stapes That's only faintly seen right here and You're about to see the oval window, which is the location at which the stapes flip plate Inserts to the vestibule So as we continue a little bit further downward we cross that oval window here and Cross to the section which shows the structures of the Hypotempanum so we have the epitempanum, which is sort of the upper portion of the middle ear cavity We have the mesotempanum, which is the middle portion of the middle ear cavity And then we have the hypotempanum the hypotempanum is characterized by three structures They are the sinus timpani the little bone here, which is the pyramidal eminence and The facial nerve recess with the facial nerve nearby So that's a facial nerve recess those are the three main structures here The sinus timpani the pyramidal eminence and the facial nerve recess with the facial nerve seen just posterior to the facial nerve recess those are the main structures of the hypotempanum Right here. We find that area of the airspace that is about to connect to the basal turn of the cochlea This airspace is the round window. So we talked about the oval window where the stapes inserts at the vestibule Here is the round window which leads to the basal turn of the cochlea And you may recall I said that this is the space through which they insert the cochlear implant We're seeing just a little bit of the sinus timpani and I mentioned before that that little bone connection between sinus timpani to the round window is something called the subiculum and There's actually a connection between the sinus timpani and the oval window with the stapes and that's called the ponticulus So a little bit of Middle-ear anatomy This is the cochlear promontory The importance of the cochlear promontory is that's where we usually see Glomus tympanicum They sit right there on the cochlear promontory So I Think that's a nice start to the review of the anatomy. Let's get to some pathology. So as we slide over to the side that had the Hearing loss, which is the right side you notice that there is a soft tissue mass at the junction between the cartilaginous portion of the external artery canal and the bony portion of the external artery canal and You notice that there is a little bit of a low density rim around this mass identified as this darker area here and usually you see that darker area also on the Interior wall as well Because this is really not fixed to the bony wall or the cartilaginous wall This is a an area of seruman. So this is seruman impaction Basically earwax that we see on CT scan very frequently through the emergency room and on some of the evaluations for patients with hearing loss It may just be something as simple as earwax So earwax seruman is the most common mass in the external artery canal. It's entirely benign. It can be readily removed and Sometimes the issue is is it connected to or attached to the tympanic membrane? So you do want to scroll and identify that Separate from the tympanic membrane. So I'm going to window this a little bit more so that way we can see the Tympanic membrane nicely and it's far away from this seruman impaction So that's the first case with a little bit of a review of the anatomy. We'll go on from here