Dr. Cunningham demonstrates the round window approach for placement of an Advanced Bionics Cochlear Implant into the right ear of a patient with severe to profound sensorineural hearing loss. Emphasis on surgical anatomy and technique is emphasized as he performs this delicate neurotological procedure.
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1. Incision and Mastoid Exposure
3. Opening of the Facial Recess
- Identification of Mastoid Anatomy
4. Round Window Preparation
- Reviewing Anatomy
5. Drill Seat for Cochlear Implant
- Create Subperiosteal Pocket
- Drill Electrode Channel
6. Securing the Implant
7. Electrode Placement
- Round Window Membrane Incision
- Electrode Insertion
- Fascia Graft
Can I have a 15 blade? Is it alright if I start? Our skin incision is a lazy S type postauricular incision. We’ll carry this incision all the way through the skin and subcuticular layer and then connect with our superior vertical limb. Can I have a pair of pickups please? Superiorly, we’ll carry this incision down to the level of the temporalis fascia, through this loose areolar connective tissue and then further elevate inferiorly. Can I have a weitlaner now please? The small one. Pick ups.
We're down now to the level of the temporalis fascia. Bovie. Now can I have a large, self-retaining. This underlying temporalis muscle and muscle periosteal layer is now incised in a similar fashion. What's the Bovie on guys? Can we go up 40? Can I have a pair of pickups - pickups with teeth? Lempert elevator please. We will now back elevate this temporalis muscle and periosteal flap to expose the mastoid cortex. Anteriorly exposed to see just the posterior bony external auditory canal - and as it curves superiorly. Bovie. Hold that. Now we’ll reposition our weitlaner. Suction. Can I have that suction please? Yeah. Leave that.
So now we have the root of the zygoma, external auditory canal, sign of henle, mastoid tip, posterior border on the mastoid. Next we’ll take the drill and the microscope. Rotate that - the base around that way a little bit. Suction. Can I have a bipolar? It’s okay. It’s 45. It's fine.
Can I have the drill please? We’ll look at the landmarks for our mastoidectomy - anteriorly, the posterior external auditory canal - superiorly, root of the zygoma, which corresponds the level of the tegmen and the mastoid tip. Water on. Okay, yeah. That’s good. Yeah, this is a 4 cutting burr. As an initial dissection, we're going to go through the cortical bone, and really we just want to get down to the level of the antrum. We’re seeing a little bit of the sigmoid sinus there, so she may have a little bit of a anterior positioned sigmoid. I'm going to try to leave some overhanging edges, as I drill the mastoid, which is a little bit different from what we do if we're doing a mastoidectomy for chronic ear disease.
And, now we are down at the level of the anthem. There is the sigmoid sinus that we can see underneath this here, and I'm also going to undercut some of this bone towards the tip as well as along the posterior aspect to help facilitate placement of the electrode later on. Table away please. Other way. Keep going - keep going - keep going - keep going - keep going- okay.
There’s my lateral semicircular canal. If you can see there Scott. I'm going to thin the posterior canal wall cause we start to work toward the facial recess. It’s like what you said - you're less focused on getting the tegmen and sinus or anything like that? Correct. Really we want to get down to the level of the antrum, so we can start opening the facial recess. Very important though that when we do the mastoid dissection, we undercut this bone - especially inferiorly - as the electrode comes in from posteriorly, it allows it to then coil up in this area of the mastoid tip. So we do want to leave overhanging edges in this instance. Now a three diamond burr please. Can I have a bulb irrigator?
As a resident, can you talk about the boundaries of the facial recess and what defines the facial recess? Yes. Can I have a number 7 section please? Yeah, mhmm.
So flat’s still pretty big. How about a 5? This just looks huge. Okay. So let’s look at our mastoid anatomy now. May I have a gimmick? So we have tegman superiorly, mastoid antrum with lateral semicircular canal posteriorly, sigmoid sinus and then mastoid tip inferiorly. Our next step is we're going to open the facial recess. Facial recess is bounded by the fossa incudis superiorly, facial nerve medially, and the chorda tympani nerve laterally. Diamond burr now. Let’s extend that.
This is very different from the cutting where you were using. So this is a regular diamond burr. Diamond burrs are often graded as fine diamond or coarse diamond. The coarser are the diamond, the more cutting power it has, but in general, diamond burrs are considered safer - especially around soft tissue structures, as they're less likely to cut right through them. Although you can still injury soft tissue with a diamond burr. Diamond burrs are good also to stop bony bleeding, so here if I'm just controlling some of these small vessels on the sigmoid sinus. Table away please.
More water Lorna. Okay, so through this - okay that’s good - through the reflection we can actually see the - start to see the incus underneath the antral opening here. I'm going to start my dissection of the facial recess drawing at the - drilling at the level of the short process of the incus and carrying that all the way down towards the mastoid tip, thinning the posterior canal wall as I go. More water please. I am careful even though we're doing a cochlear implant - especially in the case if a patient has residual hearing - we obviously we don't want to drill on the incus or the short process.
Here we're starting to see some air cells in the facial recess, so we're going to continue drilling at that level. Again, here's the short process of the incus. We’re drilling at the same level towards the mastoid tip. More water. Lorna, is there any way to increase the water please? Do you want to talk about the importance of irrigation especially when you’re drilling down? When drilling, yeah absolutely. When drilling around structures such as the facial nerve or vascular structures, it’s very important to use lots of irrigation. For one it keeps the - the diamond clear of bone dust. Lorna, I’m still not getting enough water.
We're going to continue. Now I'm actually thinning the buttress of the incus right here. We want to get that pretty thin, and it provides us with more exposure to the facial recess. As I'm drilling in the facial recess, especially medially, I'm always looking for any changes in the bone which may represent the facial nerve - likewise looking for the chorda tympani nerves to superiorly. We're starting to possibly be seeing chorda there.
So there’s chorda. So here we're starting to see chorda tympani with a small red blood vessel over the surface. Maybe... Alright, can I have a 2 diamond now please? So just while you're drilling over the facial nerve it's important to note too that if the patient is not paralyzed we have facial nerve monitoring electrodes set up as well. That is correct, especially in cochlear implant surgeries because we are drilling right above the facial nerve. There are lots of areas where you could possibly injure the nerve, either directly from the drill itself or possibly heat transferred from the rotation of the shaft of the drill, and so it's very important to always have the facial nerve in mind. We always use facial nerve monitoring during cochlear implant surgery. It’s very important that the patient not be paralyzed by anesthesia during surgery. I want a 2 diamond. And well tell her to get a 1 diamond too while she's down there.
Water on Lorna. I need more. Now with a smaller diamond, we're going to continue opening the facial recess. There’s the rest of the chorda going in there. Lorna, is there no way to get more water out of here? We’re wide open. It might be those irrigators - well, I think it is, but no… I just - I mean I just can't quite…
So we see chorda tympani nerve running along the lateral aspect of the fascia recess. Facial nerve medially, and we're going to continue to drill between these two structures, carrying our dissection as close as we can to the chorda to give us as much room as possible. And now we are starting to see into the middle ear. I can start to see stapes. Whitney. Right there? Now, we are in our facial recess. We’re going to remove bone more inferiorly to get better exposure of the round window niche. Anything you need to watch out for here - you’re kinda just drilling? You know, as you’re drilling low through the facial recess, keep in mind that the facial nerve may swing out laterally, quickly, so as you remove this bone, always keep in mind that the facial nerve could be there so that you don't come across it. Also, when you're drilling in and out of the facial recess, it’s important to stop the drill as you come in and out to avoid possible injury to the nerve. And as I’m drilling, I'm going to be applying a little bit more pressure on the superior aspect of the facial recess towards the chorda as opposed to the facial nerve. That’s the round window there? Yeah.
We start to see the round window niche now. Very important, I prefer to do the round window approach, so a round window insertion, and a very important aspect to this is removing bone from the posterior superior aspect of the round window. Sometimes the pyramidal process can be quite prominent, and so I will often drill a little bit of this bone away so that it doesn't interfere with our trajectory of the electrode.
And here we are seeing - can we have a - a Rosen Needle please? Irrigation off. We have pyramidal process here, stapedial tendon, and capitulum of the stapes. Well these suctions are huge - this is not normal. I’m going to remove a little bit more of this bone inferiorly. Okay. Alright now may I have a 1 mm diamond burr?
So now we have the promontory. Water off please. Can I have the Rosen please? Water off all the way, really clamp it tight cause it still comes out. So we have promontory here and the round window membrane just underneath the niche which can be seen - you don't have a different Rosen do you? One that’s not all bent up. Round window membrane, round window niche. At this point we are going to drill away this bone superiorly and posteriorly of the niche and take this bone back almost until it's flush with the membrane itself.
Drill. Water on. So Scott, you see the niche here. We don't see the membrane that clearly yet, because it’s still - there’s a little membrane over it - like an adhesion. So what - what will - what is really important when you do round window insertions is you got to take this bone posteriorly and superiorly. Otherwise, you just can't get the right angle for insertion. So we’re starting to see the angle there right? A little bit better. This suction is huge. Is anyone using other methods for taking down the round window niche or just drilling? I think drilling is probably the standard, yeah.
So now we can actually see the membrane much better. Can I have IS joint knife now? There's always a little bit of bleeding from these mucosal vessels. I don’t like these suction irrigators, but I mean I don't have a choice I don't think. So you always get a little bleeding from these mucosal vessels on the promontory. So the little round kni - IS joint knife will just kind of push these back. Kind of get them so the blood is running in an area opposite from where we're trying to operate.
Now we actually are getting a nice view of the round window membrane. There are some adhesions on the membrane. We’ll try and clean those up a little bit. There we go. We’ll kind of just bring these adhesions - these little mucosal adhesions down. And we have a very nice view of the round window membrane now.
Now we're very close, there’s - let me have that IS joint knife one more time. So we have a great view of the membrane. But see there’s a little lip still here. When we go in, when we're inserting, we're not inserting in this direction - we want to insert in the direction of the the basal turn of the cochlea, which is more angled in this direction. And so that's why it's important to get bone off posteriorly and superiorly here, and if this bone over the pyramidal process is really prominent, sometimes I'll drill that down a little bit. Drill. It’s like what you were talking about - translab approaches. If you have bone that sort of the lateral and outside, you can’t angle your instrument in deeper. Right, exactly. One of the criticisms of the round window approach, is that - is that there is the hook portion of the basal turn of the cochlea, which is just here, and when - when you enter through into the round window, it drops down before it goes anteriorly, and so if you - if you went directly in through the round window membrane, it can't make that turn. You’ll end up going right through the basilar membrane, but if you angle in the direction from - from this direction, then we can get around that turn quite easily and very smoothly.
Okay that's very good. Now can I have an irrigating syringe. 10cc irrigating syringe. Chronic cough. So we will review our anatomy now. Okay, so can I have a gimmick, Lorna?
So we have lateral semicircular canal, facial nerve, chorda tympani nerve, pyramidal process of the stapes, stapedial tendon, and then directly looking at the round window membrane. Can I have that drill one more time Lorna? Annoying vessel here. Water off. It’s not going to stop is it? Do you have a little bone wax? So - and can I have a gimmick? Can I have a gimmick? I’ve got you a good suction here now. Is it - is it a size 3? Okay. Do you have a little cotton ball or something - just put it under the light so I can see it. Okay - now let’s - can I have my eye shields back? We’re going to drill.
Next part is we need to drill our seat for our implant. So with a freer, we’re going to make a kinda of a - we're going to make a subperiosteal pocket that the implant will sit in under the muscle, but we will also drill a seat for the implant.
So now we are making the seat for our implant. This helps prevent migration of the implant. Most manufacturers probably recommend drilling a seat, but you don't necessarily have to do this. Many people just make a subperiosteal pocket and place the device in the pocket. There is a small risk though that it could overtime migrate, so I prefer to usually drill a seat.
Okay, let me have the Silastic implant. Can I have a marking pen? Okay. Now we’re going to make the electrode channel. Yeah, water on. So the electrode will be fully recessed in a channel here. Okay, diamond burr now - 3 diamond. With our diamond burr, we’ll control any further bleeding. Can I have a bulb irrigator? Water off. We want to get all of this bone dust out of here. More water please. One more. This thing can really, literally just lay flat on the skull, but they do recommend making a little anterior lip here. You don't have to drill a full well, but just more of a lip across anterior edge, and that just keeps it from being - and I usually drill a little bit of a ledge superiorly and inferiorly just to keep it from being able to move too much, but it's essentially pretty flat. That would only keep it from migrating anteriorly though, right? Yeah, it could migrate posteriorly, and there's no way - there's not really a way you can drill a posterior lip, but that's where fixation kind of helps prevent that. You don't have to drill this ledge - some people don't. They just put it into a pocket.
Now we'll take the implant and then the mersilene and the screws. And it sits down in there quite well. Mayo scissors. This is mersilene tape, which is often used for cerclages, and it's a nice little strap that can be used to anchor the implant. Let's have a sin retractor. This is a permanent material. Can I have a 15 blade for a moment? Just push back that periosteum a little bit. Okay, and if someone can hold this. Can I have a screw? And we're just going to anchor this in there. Be very cautious with our electrode. You can come out with that - I got it. Then Lorna, if you can hold up here. Did you just - you're just - you just anchored that and the bone on the inferior aspect, correct? On the anterior, yeah. I’m going to have to come over here. Lorna, hold on for one second - let's come back this way, right like that. Can I have a pair of smooth forceps? 15 blade? And we'll just cut off the excess - let's have smooth forceps. I got them. Here we go.
Alright, now our device is now secure. We'll go back to the microscope, and can I have a 5 suction now? And I'm going to need a 24 suction in just a minute. Table away please. Do we have any Decadron? Like a little liquid Decadron we can load into a tuberculin syringe? Yeah, can I have a vial? Keep going. Okay, that’s good. No, I'm going to squirt this around the round - the round window. Let me draw that up Robin. Four milligrams. 18. Don't stick me. If you’ll just keep that back there for a moment. Now the 5 suction - the plain 5 suction. I’m going to at least scrub for closure. Can I have an irrigating syringe for a second, Lorna? Are you supposed to what, Lorna? I will in just a second - yeah, I will in just a second. Okay Lorna, let me go back to a plain 3 suction, and then in a second I’m going to go a 24. Yeah, takes a lot to get all this liquid out of here. Now a 24 suction and then that Decadron.
So she really has pretty severe to profound hearing loss in this ear, but the she does have a little tiny bit of residual hearing, and I guess these don't vent so well. So I am going to put a little bit of Decadron - 4 milligrams per mil - around the round window membrane. Steroid now. And we’ll just put a few drops around there. Kind of lessen that a little bit. Now, next can I have a 59 10, sickle knife. I like to make a little small vertical incision in the round window membrane, so that the posterior part of the rounded membrane act - almost serves as a little bit of a shelf to help guide the electrode in. I’m going to get rid of this and push it down. Can I have a barber needle for a second? There. Okay, I want the 59 10.
So we're going to make a small incision - vertical incision in the round window mem... Okay and then, a small vertical incision. And then, the electrode forceps and the alligators. We’re going to take a… Our electrodes - want - you want these to be facing the medialis so the stylet is usually pointed down towards the six o’clock location. We're going to be advancing this electrode off the stylet. And the angle I'm coming in is - I'm going to get it in the opening first, but then I'm going to angle more superiorly. Can I have now the electrode? Once we get to the blue marker, we're going to grab the - I'm sorry that jewelers forceps - we're going to grab the stylet, and very carefully advance this, and slowly off our stylet, all the way down.
Now can I have the jeweler's or - actually, hold that. Here's the stylet, and we are almost at the blue marker ring. We’ll just give it a little bit of a push in, and now we are completely in. Can I have a Rosen - actually, do you have a pitchfork, Lorna? Nah, that's okay - no I’m good, we’re good. It’s - nah - it’s good, it’s perfect.
And so we now - let's have a something to point with like a barbara. So the blue marker ring, the electrode is advanced to the second blue marker ring, so we have a nice full insertion of our electrode today.
Next I'm going to take a very small piece of fascia. Can I have a sin retractor? And we'll put a very small fascia graft around that electrode at the level of the cochlea - round window to seal that area a little bit better, but it's already a pretty snug fit right now. Let's have a pair of metzenbaum. I've got it, yep. Hold that Lorna. Can I have iris scissors and a pair of smooth forceps? Smooth forceps. Now, can I have a 15? Lift up a little more, straight up Lorna. Can I get a fascia press? Okay, let’s… Now… A 15 blade. Can I have a Barbara? Okay, and now he will place this graft gently around the electrode at the level of the round window. Perfect. Okay. And that is that.
Now we have the electrode still out of the mastoid. Can I have the jeweler's forceps? We are now going to let this sort of coil up in the mastoid, and then - again, we previously left these overhanging edges that helps this electrode to coil up in here can settle nicely, back here.
There - that is that, and now we will go ahead and start closing.
Can I have a pair of eye shields please? Sorry. Okay, 3-0 biosyn - uh, no, biosyn. Table back towards me. No, no, I just use biosyn for the whole thing. Yeah. Okay, that’s good. If you’ll just hold this ear down for me, Lorna. This is a 3-0 biosyn. I just typically use the biosyn for the deep and more superficial layers - the same stitch. We're going to actually re-approximate this muscle periosteal layer. Now is the mersilene tape something you kind of just decided on - decided on yourself to do, or had you seen that somewhere? No, we used to - we always used the suture like a large heavy prolene or nylon suture, and I can't remember where I - I must have seen it somewhere, but we had it available here, the mersilene. They used it for cerclages and just started using it. Kind of thought it would be a pretty simple thing to put two screws through the - oh absolutely - through it, and it just secures it place. And this is why you like the 7 incision as well - yeah. The periosteum layer - I mean, people have gone too much more minimal incisions. It's hard to get back - you know, get your implant far enough back, and also drill a well if you like to do that. But a lot of people will make a - a smaller incision, and without this extra limb here, and just make a subperiosteal pocket and tuck the implant into that pocket. And that works fine, but every now and then you may get a device that over - overtime, you know, migrates superiorly. And a lot of - most of the time, that doesn't cause a lot of issues. I have seen patients before who have had implants that weren't fixed, and that it - it started causing pain once it migrated, and so we just repositioned it. But I still kind of like to secure it in a seat or well - or at least in a ledge that will keep it from - from moving forward.
I may need one more of these biosyns. You don't open it, but if we can - if we'll just - if we can just have it in the room. I'd love to be able to show this - this one was a really nice exposure that you could - that you could see it all really well, and it went in very very smoothly. This electrode is pretty easy to put in. Let’s get these electrodes out.
And so we wrap around the head and make sure the gauze is above the ear, and we want to go very low on the neck so you're below the occiput. Otherwise, it will ride up her neck and right off of her top of her head. So feel it come way - make sure it's over the ear, way down low on the neck. Bring one now up over the top to secure that top portion. Yeah, can I have - you can put it back under now. Get the scissors. Come back this way. You got any scissors on you?
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