 For the next 30 minutes, I'll be discussing the postoperative temporal bone. And specifically what we'll be discussing are mastoid ectomies, approaches to the internal auditory canal, various acicular reconstructions, and briefly talk about imaging after cochlear implants. Well, the most common type of procedure when we look at various types of mastoid ectomies is for this disease entity, which we can all identify as a cluster eutoma. So here we see the head of the malias, we see the anterior and posterior cruises of the stapes, but we don't see the short process of, excuse me, the long or short process, the incus or the capitulum and the stapes. So this is a classical example of a cluster eutoma. And this is what the surgeon sees typically they see a pearly white mass. Now, when the classic procedure that's performed for a cluster eutoma is referred to as a canal wall up mastoid ectomy. So this is usually formed for early cluster eutomas. In fact, here's a small pathologically proven cluster eutoma that extended superiorly into the space here, which is referred to, excuse me, as Prusak space. Now, in a canal wall up mastoid ectomy, as mentioned, this is typically performed for for early cluster eutomas, we can see a classic mastoid ectomy defect but notice how the posterior wall of the external auditory canal is intact or otherwise known as up. So this is a canal wall up mastoid ectomy. Now, for mastoid ectomies that are a little bit more extensive but in general have not involved the ossicles. This is the type of procedure that's called the canal wall down mastoid ectomy, where the surgeons remove the posterior external auditory canal so in this case the canal posterior canal wall has been taken down. Here we see the remnant of the external auditory canal, and here's our mastoid bowl so unlike the prior image, where the posterior external auditory canal was maintained. In this case the canal wall has been taken down, but they have preserved the ossicles are made every attempt to preserve the ossicles. And in this case we can see preservation of the Malleus and the Incas and the state piece. Now, in very extensive cholesterol eutomas, then they can perform this type of procedure which is a canal wall down mastoid ectomy with ossicular resection. Sometimes, this is what's referred to as a radical mastoid ectomy. So in this particular case they've resected the external, the mastoid air cells have taken down the posterior wall of the external auditory canal. And they've resected the ossicles in this particular case they've maintained the anterior and posterior cruise to the state piece in this schematic illustration. And here's an example of a canal wall down mastoid ectomy with ossicular resection. Here you can see the anterior and posterior cruise are maintained. You can also see that the tympanic membrane here is abutting the state piece and this is what's referred to as a type three tympanoplasty so the surgeons can reconstruct the tympanic membrane and when that tympanic membrane lays on the state piece. This is what's referred to as a type three tympanoplasty. In this particular case they've resected the performing mastoid ectomy, resected the posterior wall, the external auditory canal, and all of the ossicles have been resected. So this is a complete resection of the ossicles. And again, the other terminology you may hear is a radical mastoid ectomy. So this can be very helpful, at least to try to assess for closteotoma. So here's an example where we can see here of a patient that's undergoing a canal wall up mastoid ectomy. When we see something like this, we are pretty sure that the initial closteotoma was probably pretty small. So when we do see a mass here involving the external auditory canal right at the junction of the tympanic membrane at the external and middle ear cavity, then we can say with a pretty high degree of confidence this is closteotoma. And why? Because with the canal wall up again, it should have been a pretty early closteotoma. So when we do see a focal mass and we have to think that, hey, anything that does grow back is probably closteotoma. Here's another example. This is a patient with closteotoma involving the superior aspect of the middle ear cavity and the epitympanum. And here's another example of recurrent closteotoma. And what we see here is that they're thinning of the roof of the tegman sympathy. So two examples of recurrent closteotoma. And this patient was status post canal wall up mastoid ectomy. Now here's an example of a patient that's undergone a canal wall down mastoid ectomy. We can see the head of the malleus here. And then we can see a soft tissue mass here located anteriorly. Now, based on this alone, it's pretty hard for us to say whether or not this was recurrent closteotoma. In general, if I see a focal mass like this, and I know the patient's undergone a canal wall down mastoid ectomy, it's pretty extensive disease. And this is actually distal to the minimum rhythm alley. So this is hard place to get too surgically. So I'm more inclined to think that this was recurrent closteotoma and indeed it was. Here's another example of patients undergone a canal wall up mastoid ectomy. We can see this focal soft tissue mass extending into the region of the oval window. You can perform MR. And when you do perform the MR in general the standard techniques the standard sequences can be a little bit non specific. So this was an MR that was performed with contrast, closteotomas in general do not have a lot of enhancement. In this particular case the facial nerve had gone out so they had a facial nerve palsy. And when we look at the tympanic portion of the facial nerve we can see abnormal enhancement compare that to the opposite side so in fact this was recurrent closteotoma that had proceeded to give and had an irritated the facial nerve causing a facial nerve palsy. Now, I think all of you are familiar with the use of diffusion imaging in recurrent closteotomas. I have to admit I there's a lot of literature out there. We do not have line scan diffusion that is a classic diffusion technique used to image closteotomas I still perform diffusion imaging for closteotomas. I do find it very helpful when you have larger closteotomas. When you have smaller closteotomas I worry about the negative predictive value so very very small closteotomas. A negative study does not mean closteotoma is not there it just means you just may not be able to detect it. So here's another example of a patient that's gone multiple under multiple mastoid ectomies and we see this residual mass right here in the mastoid cavity. We perform the diffusion imaging there's a bright signal here here's the ADC map we can see it's reduced signal. So this was pathologically proven recurrent closteotoma. There's been a lot of work out there talking about what can this replace second look surgery. In general I've always performed CT some have performed MR. I have to admit I still like CT, in part because I can see smaller smaller lesions. The classic way is to perform non EPI imaging line scan diffusion all of our magnets have EPI but again I still do it. And again I like it for larger closteotomas but for smaller recurrences I think it's kind of hard. As a result I've always worried about the volume of disease and the negative predictive value which is linked to the volume. In fact I know they're performing a lot of MRs in order to replace second look surgeries I think that's fine. In the US I think it's plus minus I think some academic centers are doing it I would say for routine practice. They're not performing MRs to look for recurrent closteotoma and similar in Canada I think it's very variable. The take home message is I think MR with diffusion can be helpful to evaluate for recurrent closteotomas, but I do worry about the volume of disease and as it relates to the negative predictive value of the study. Here is an example of recurrent closteotoma just an example of a potential complication. Here we have erosion of the lateral semi circle canal and we can also see erosion of the tegman timpani. Here's another potential abnormality associated with recurrent closteotoma. And what we see here is absence of the tegman mastoidium. So we have to be very careful in when you're evaluating patients that in this case have undergone a canal wall up mastoidectomy played close attention here to the roof of the tegman timpani why because when you see the soft tissue extending in fearly from the tegman timpani. This is an example of a small herniation of the temporal lobe through this operative defect, compare this right side to the left side so notice this little bit of defect extending in is a post operative encephalosial following a temporal bone resection. So we've covered the various mastoidectomies now we'll cover approaches to the internal auditory canal. Now approaches to the internal auditory canal are typically performed to respect vestibular schwannomas. So here's just a class of example of a vestibular schwannoma. We know they arise in the internal auditory canal and they most typically involve this nerve right here which is the superior vestibular nerve. There's a couple of approaches to resection of vestibular schwannomas. One approach is referred to as the retro sigmoid approach so in the retro sigmoid approach this is done typically in clap collaboration with neurosurgery. What they do is they perform. Excuse me a posterior phosphor craniotomy, and this allows them access to the posterior aspect of the petrus apex. Now once they come to the petrus apex they can drill away that superior portion of the petrus bone as a scene here, and it gives them access, in this case to the superior vestibular nerve and the facial nerve is at that level. In general retro sigmoids are performed in patients that still have hearing. And it's oftentimes an attempt to remove the vestibular schwannoma, such that you can still preserve the hearing. So here's an example again post opera fully a retro sigmoid approach we can see the posterior faucet defect, and we can see a resection of the petrus apex so that's our classic retro sigmoid approach. The next approach that's performed is typically performed by the neuro otologist and this is what's referred to as a trans labyrinthine approach. So the neurosurgeons are very comfortable going into the posterior fossa and pulling away brain the ENT surgeons like to stay out of the brain. And one of the ways to perform resections of vestibular schwannoma is they can end up in the same place but on the other hand they have to drill through the mastoid air cells and the inner ear. As a result, this type of procedure is oftentimes performed in patients that have already lost their hearing, because it's harder to get proper visualization of the extra of the internal auditory canal from this type of approach. So what do you look for post operatively. So in this particular case we can see the bone of the posterior faucet is intact. In all of this surgery has been localized to the mastoid air cell and the petrus bone and here we can nicely see this defect involving the fundus of the internal auditory canal. Also post operatively we can tell on MR because this is the classical appearance that we see on a non contrast T1 weighted MR. Typically these are filled with fat. So this is a nice fat graph that's been plugged into the mastoid ectomy defect. So if you're ever looking at an MR and you see this wedge shaped area of fat. That typically means a patient's undergone a trans labyrinthine, a mastoid ectomy. So here's an example pre operatively we can see this vestibular schwannoma extending into the right internal auditory canal. This was the same patient that had been undergone or section this is a trans labyrinthine approach, we can see that it's been packed with fat. But if you look on the corner of the film this is something we don't want to see. This is a little migration of fat droplets into the posterior fossil so unfortunately this is migration of this fat graph into the posterior fossil. Another complication that we may see is necrosis and basically fat necrosis after the fat graft has been placed. So this is the patient that underwent a trans labyrinthine approach we can see fat here in the mastoid ectomy defect. And after time, this patient actually underwent fat necrosis. And here we can see a fluid fluid level, following a necrosis of this fat so here's our fluid and there is our our debris. So the next thing that we'll discuss are ocicular reconstructions. Now, a secular reconstructions are a little bit more complicated. But on the other hand, if you understand what the neurotologists are trying to do they actually make a fair amount of sense. So first of all, ocular reconstructions are performed in order to create the normal ocular chain so the normal ocular chain runs from the tympanic membrane to the oval window so you have the head of the Malias. You have the Malias to Incas and the state these. And anytime that you have some type of process that disrupts that mechanical chain, somehow you have to figure out a way to recreate that mechanical change. The normal ossicles, as I mentioned before are located here on your left so these are normal ossicles and they go from the tympanic membrane all the way into the oval window. The two primary types of ocicular replacements are the following. There is something called a pork, which is a partial ocicular replacement. And in this particular case, the stapes is maintained. And what the surgeons try to do is to create some type of bridge if you will from the tympanic membrane to the stapes, a total ocicular prosthesis is when there is no stapes and somehow they have to create this chain that extends from the tympanic membrane to the oval window so there's a partial ocular replacement, and then there is a total ocular replacement. So let's first talk about our partial ocular replacements. So a partial ocular replacement is typically performed, as I mentioned before, when the superstructure of the stapes is intact. So in this case we have a colostia tome that's eroded the Incas, but the stapes is intact. So from a surgical perspective, what they're trying to do is recreate this change. So here is our stapes that's located here. Here's our tympanic membrane. So they want to create this prosthesis that goes in the tympanic membrane that attaches to the head of the stapes. So this is an example of a partial ocular replacement prosthesis. So here is the ocular prosthesis. Here with a leap of faith we can see the stapes and here is our oval window. So in this case the stapes is maintained. The Incas was eroded and this flat portion right here abuts the tympanic membrane. So you can see if there's any motion here this is directly transmitted to the stapes and the stapes directly transmits this to the oval window. Another example here, this was a patient whose stapes was intact. There's our oval window. This little hat right here, this round structure attaches to the tympanic membrane. So again, if you have sound waves coming here, it's beating against this porp and again that directly transmits it to the oval window. Now these are examples of porps that have been displaced. So on the top left hand corner we can see a stapes here. We can see the head of the malleus here, but unfortunately this patient had a excuse me, this was what they needed to fix and this was actually the prosthesis that was intended to go from the tympanic membrane to the head of the stapes, but unfortunately this was displaced. Here's another example. This patient underwent resection for Colesiotoma. We can see the stapes here. We can see the maneuver the malleus here. This in fact was the prosthesis. This prosthesis should be oriented such that it's attaching to the head of the stapes, but we can see that this has been unfortunately displaced. So these are two examples of displaced partial ossicular prosthesis. Now this is a specific type of a partial ossicular prosthesis. This is what's referred to as an Incus interposition. So what an Incus interposition does is the following. Here we have the stapes that's located in the oval window. Here we can see the malleus. Now normally there's an Incus that goes between the malleus and the stapes. In an Incus interposition, the Incus is somehow disruptive and what the surgeons do is they remodel this Incus, such as a portion of this extends from the malleus and extends all the way into the stapes. Thus you can see they have maintained or recreated this mechanical ossicular integrity. So this is an example of an Incus interposition. So we're all experts right now. This is a canal wall mastoidectomy. This is the head of the malleus and with the leap of faith you can actually see the triangular portion here of the short process of the Incus. And thus just deep to this is going to be the stapes. So this is a classical example of an Incus interposition. Here's another example of an Incus interposition. So here is the head of the malleus. This is the short process the Incus. I should say this is the maneuvering the malleus. This is the Incus interposition. This is that remodeled Incus. And again you can see this is a short process the Incus and just deep to this is the capitulum of the stapes, which is attached to the stapes. So again, if you look at this image on the bottom right with the leap of faith you can see the wedge shaped appearance of the Incus and you can see how it's been remodeled. So an Incus interposition is a specific type of partial or secular replacement prosthesis, in which case they remodel the Incus. So here's another example of an Incus interposition. Here's the head of the malleus. This is the Incus. And here we can see the anterior and posterior cruises of the stapes, and we can see that this ocicular integrity has been maintained. And on the other hand is an Incus interposition that has been displaced. So here is the maneuvering the malleus. Here's the head of the malleus. There should be a short process here. You can see that it's the short process has now been remodeled. You can actually see the groove that's been created by the ENT surgeons by the neurotologist, and we can see the stapes. So unfortunately this stapes has been unroofed. And this Incus should normally communicate between the maneuvering the malleus and the head of the stapes, but we can see that it's subluxed and displaced. So unfortunately, this was an Incus interposition that became subluxed. So we talked about partial ocicular replacement prosthesis. Now let's talk about total ocicular replacement prosthesis. And these are the ones that go directly from the tympanic membrane to the oval window. And these types of procedures are typically performed when the stapes has been eroded. So here's an example of a large colestiaeutoma. We can see the malleus that's been displaced anteriorly. There's no Incus and when you look at the oval window, there is no stapes. So this type of surgery would require a total ocicular replacement prosthesis. So the torps run all the way from the tympanic membrane all the way into the oval window. So this is a clinical example of a torp. So here this flat plate abuts the tympanic membrane. And the shaft right here goes to the oval window. So we can see how this top right image correlates with the left side image. And here's another example of a torp. So this flat plate abuts the tympanic membrane, and the shaft goes all the way here into the area of the oval window. So you can see if there's soundways coming laterally in a butts and tympanic membrane, and it pushes against the oval window. So here's another example of a normal appearance of a torp. This patient had a canal wall down mastoidectomy for colestiaeutoma. So if the stapes was eroded, we can see this abuts the tympanic membrane. There's the shaft that goes to this foot plate and the foot plate abuts the oval window. So really just by looking at understanding the type of surgery was performed and the type of prosthesis, you can create the history, you know exactly what this history was. Here's another example of a torp. So this is the torp here, this flat part goes against the tympanic membrane, and directly communicates with the foot plate that goes into the oval window. So anything that beats against the tympanic membrane is directly pushed against the oval window. And one other type of torp, this is a different type of torp. This has that little rounded hat on it. It has a central shaft that again goes into the oval window. And again, this area right here, this roundness directly abuts the tympanic membrane. Two more examples of a torp. Here is an example of a torp that here is that flat part against the tympanic membrane, and this directly abuts the oval window. Now here's an unfortunate type of torp right here. We can see that this torp is discontinuous. Unlike its brethren on the left, which is continuous, we can see there's an airfield gap between the flat part and the shaft. And notice how the distal part of the shaft is separate from the expected location of the oval window. So this is a subluxed torp. So, another type of torp, if you will, is a stapedectomy. So what happens with the stapedectomy is that the incus and the malleus are actually preserved, but in this particular case, there is selected replacement of the stapes, hence the term stapedectomy. So this is an example of the stapedectomy. Here is the head of the malleus, short process the incus, and here is the stapes prosthesis. Sometimes they call this a piston prosthesis. And this is typically attached to the incus, and sometimes you cannot see this communication that goes to the incus, but you can see the piston that pushes against the oval window. This is typically performed in otosclerosis. So otosclerosis is a unique disease of the otocapsule. It's primarily autosomal dominant, more common in females. No one really knows exactly what causes it, but it's felt to be abnormal resorption and deposition of bone in the labyrinth. So, on the left hand side is a patient with otosclerosis and on the right hand side is the pathological image. So if you look first pointing your attention to the right hand side, this is the oval window that's located on the right. And if you look closely, there is this area of newborn bone formation just to the anterior aspect of this oval window. This anterior aspect of the oval window corresponds to where the anterior crux of the stapes attaches. And this area right here at the oval window is the stapes foot plate. The point is, is that if that anterior attachment attached right here into this new bone formation, and this part of the stapes foot plate went into this new bone formation. That means the stapes could not normally vibrate. In fact, this is what's referred to as stapes fixation. Now let's turn our attention to the left. Here is our vestibule. Here's the anterior crux of the stapes. Here's a posterior crux of the stapes. Here is the tympanic membrane. You can see this anterior crux of the stapes and right where the foot plate is is attached directly to this new bone formation. So this is what we refer to as otosclerosis and it's involving the oval window so this is finestral otosclerosis. Clinically this diagnosis is made at surgery by literally the surgeon going in there and wiggling the stapes and that's that stapes does not move it is literally fixed. And if it is fixed and the surgeons have to take out the stapes and attach a new stapes. And this is what's, and this is why they have the stapes so in this particular case here's ahead of the malli is. Here's the short process the Incas, and you can see this small little area here the small little prosthesis extending from the Incas, all the way into the oval window. So unlike the other torps if you will in this case it's just the distal aspect of that torque that's been resected. Now in this particular case on this coronal image we can see the tympanic membrane here, this area at the top is a skew them, but notice how this piston prosthesis right here is completely separate from the tympanic membrane there no problem. So this was again, an example of a piston prosthesis, but we're a little concerned here because we don't see that a second or integrity. Another example here this was a piston prosthesis that extended to the oval window and one other example here of a piston prosthesis sometimes you won't see that attachment with the Incas so you can say it's displace it just may not be radiologically visible. But again that's a relatively normal appearance. And these on the other hand are abnormal appearances. So this is an example of a stapes prosthesis where the tip of this has been displaced from the oval window. This was an example of a stapes prosthesis that's been so this prosthesis become bent, and this patient had a persistent conductive hearing loss. This patient ended up having vertigo and dizziness after the prosthesis. And this was an example where the prosthesis pierced the oval window, and the tip of the prosthesis is literally in the vestibule. And the reason this patient was dizzy, dizzy is that this prosthesis was either sticking into the saccule or the uterical, and because they are the organs are associated with balance that's why this patient became dizzy after the procedure. The last thing that we'll talk about is post operative imaging after cochlear implants. So when a cochlear implant is performed extends from the outside, the electrode extends through the mastoid air cell. It goes through the epitimpinum into the mesotimpinum and then into the cochlea where extends through the scale of timpani. And typically the cochlear electrodes tend to have two and a half turns. So a commonly performed way to evaluate this and certainly when I grew up was just to do a plane film so here we can see the little pigtail of the electrode and literally you can count the number of electrodes so different types of electrodes have different little markers here so it really varies based on the electrode. So when you perform the plane film what you want to make sure is that it has a round appearance but unfortunately in this case we can see this electrode here is not round but it's straight. So this would tell us that in this particular case this electrode was not properly placed. So these were both taken in the operating room so one way to do this initially in the operating room the ENT surgeons the neurotologist tend to take a quick plane film to see whether or not this has a normal rounded appearance. Now you can perform CTs for this I know some of my colleagues are doing cone beam CT specifically to look for placement of the electrodes. I don't really know how common this is but I know some people in Europe are doing this we tend not to do this routinely. In general what our autologists tend to do is they place the electrode they make sure it does have this configuration, and then they turn it on and they see if it's activated if it's activated and they're actually activating the cochlear nerve. So in general they're pretty comfortable with it, but if you do perform CTs. One way to look at this is make sure that you window down so you sort of blur out the background so you can enhance the metallic component of that electrode and you can see a very nice pigtail appearance corresponding what we should see on the schematic illustration. Another example here here's a normal appearance of the electrode we can see that it's in the proper location in this case the middle terms of the cochlea. Here's a sagittal reconstruction again demonstrating the normal appearance of the electrode within the location of the cochlea. Another example here this is pre-op this is post-op in this case we can see they did a small little cochleotomy here at the cochlear promontory. Here's the placement of the electrode going into the region of the small cochleostomy defect extending into the round window. And here we can see the normal appearance of the electrode corresponding with the pre-operative appearance. So this was a good appearance of that cochlear electrode. What if you have a situation here that looks normal and now you have something that does not look normal what are some of the things that you should look for. Well if you do see that abnormal appearance that I think and the surgeons do not does not want to pull out the electrode. Then you can perform CT because a CT can better guide you as to where that electrode actually is. So this was an example where the electrode just ended up coiling into the middle ear cap he never made it into the inner ear. Another example here of where this electrode actually probably came out of the cochlea notice it should be extending into the basal turn the cochlea but it never made it it's actually outside of the basal turn the cochlea. Here's an example where the electrode went straight and this extended into the cochlear canal. Now the cochlear canal is a canal that really it's not really patent. But occasionally it if sometimes it's it's sometimes that the fibrous tissue is not completely formed so when incredibly rare cases you can see this cochlear this electrode extend through the cochlear canal. Here's an example unfortunately where the surgeons got a little confused and they ended up placing the electrode into the carotid canal so here's the current images demonstrates the carotid canal and we can see a small little cochlear electrode, a buddy in the carotid artery. And here's an example where they ended up pushing the cochlear canal and they drilled and it ended up going into the clivis you can see actually across the Petro-Cliber Fisher. So if you do have that abnormal appearance on plain films and the surgeons don't want to pull it out, then you really should be going looking at a CT scan to see whether or not, or what exactly where that electrode is because it can end up in some strange places. So in summary what we've done over the last 30 minutes or so was talk about mastoidectomies. We talked about approaches to the internal auditory canal. We talked about ossicular sections, and we talked about cochlear implants. Thank you very much for your attention.