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SNI, Surgical Neurology International, with Nancy Epstein as its editor-in-chief, and SNI Digital, a new editorial created neurosurgery and medical information multimedia platform, with operative
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videos, expert interviews, podcasts, global interactive discussion of information for the next generation of clinicians in 13 languages. With James Hausmann as the editor-in-chief,
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our police to present another in the Skoll-based surgery series from the University of California at Irvine, Department of Neurosurgery, Interdisciplinary Skoll-based Surgery Team
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The title of this presentation will be how we manage acoustic neuromas, the anatomy, molecular biology, and clinical judgment behind the surgery
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Dr. Sue is a professor of Neurologic Surgery, Biomedical Engineering and Alluringology. He's the chair of the department of neurosurgery at the University of California, Irvine.
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Edward Kwan is a professor of otolangrology, division chief of radiology and skull-based surgery, and the co-director of the comprehensive skull-based program at the University of California and
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Irvine Dennis Mokasian is a professor emeritus in the department of neurological surgery, director of the neuroanatomy and skull-based laboratory at the University of California at Irvine, and
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Alexander Himmstead is a PG-MI for a resident physician and neurosurgery at the University of California at Irvine, Alpha Omega V, PCA, research award, Christopher Megurant's award and a senior
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student with the most honors and promise of 20, 022
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you went to the Chapman University, graduated Sima Cum Laude. Okay, so
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we're back here again with the
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Skoll based team from the UCI University of California at Irvine. And we have Frank Su, who's the head of neurosurgery at Kwan, who's an otolaryngologist and Skoll based member of the Skoll based
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team
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Denny Mancasian, who is a basic scientist and a surgeon and a whole bunch of other things.
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And Alex is a young man who went to the barber and the barber won.
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Okay, terrific. Okay, Alex, why don't you go and we're anxious to see what you got to say. Okay, great. Well, thank you again for having us on the SI digital platform. It's truly an honor to
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be here and to get to share some of our cases.
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I will share my screen here. Let's see.
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So continuing our UCI Nursery School-based Case Conference.
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So last time we were on, we talked about a claval cordoma and a spina doing meningioma. Today we have two possibly three cases that I wanted to discuss One is a vestibular schwannoma, and one is a
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thrombost for tubular aneurysm. And the third is olfactory groove meningioma. So we'll see how far we get.
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And the format, I'll give a brief presentation. And then Dr. Mulcazian was kind enough to work with me to make
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very solid in-depth neuroanotomical slides. Mostly for the vestibular schwannoma a little bit for the
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for the far lateral, but we'll we'll hope to cover the far lateral. neuroanotomically in a little bit more detail in a future session. So to get into it, this was a 41-year-old male who presented
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a couple of years ago to our clinic with left-sided hearing loss for three years. He had constant tinnitus and no serviceable hearing on an audiogram. However, his spatial movement was intact.
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Otherwise he had no focal deficits and was living his life
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The MRI that we got in clinic showed this 35 centimeter left CPA-enhancing mass that was extending into the IAC or maybe I should say extending out from the IAC, causing mass effect from the
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brainstem, making it a coosgrade 4.
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And so our plan quite something was a left retro-sigmoid craniectomy for resection of the mass with neuro otology assistance.
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And so, now we can get into some of the anatomy from Dr. Melchazian. So, these slides are covering posterior or transmeatal anatomy and surgical approaches to the posterior
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fossaserbular pontine angle lesions. These are this is a non-comprehensive, although quite in-depth summary of some of the anatomy that we have here. This is a brief outline.
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And so, here is the external anatomy where you have the area
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behind the ear where the surgical where the surgery is focused. You have your transverse sinus coming down to the sigmoid sinus. This kind of shows the area of the door opening and then down over
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here is a schematic that focuses on the
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asterion, the junction of these three sutures. lambdoid, pride of mastoid and occipital mastoid. And then here's kind of a zoomed in view of what happened of what you see when you open the skull
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and you're looking at the cerebellum.
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This is some of the collateral anatomy, as Dr. Mukasian likes to say, of a left suboxypical approach. So, we can see these red markings refer to the occipital artery, which is nearby, often
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encountered during the retro-signoid approach, and then the greater occipital nerve, which is usually not appreciated, but it's good to know that it's there. Then we also have the occipitalis
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muscle attached to the superior nucleoline, and then the semispinalis capidus and spleenous muscles, which are important, posterior cervical
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structures. Can I ask you a question? Please. Could you go back to the first slide for me? This is, that's very good, and Denny, I assume you made all these diagrams, is that right? Yes. Yes.
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I think the other. I'm responsible for all the errors and mistakes. No, I thought. Let me ask you a question right here Why do you expose the sinus?
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I think you don't, well, there are two reasons. One is it tells you you're far enough lateral to be orthogonal with a long axis as a cerebellopontine angle. If you look at the transverse and
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sigmoid junction, you see the superior petrosal venous, durovenous structure, right? And those are classically known with some variation to be pretty consistent. If you look at the other venous
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structure, it's a superior petrosal vein.
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And it's a Y-shaped that goes into the more anterior, yes, more anterior part of the superior petrosal venous, durocynus, which can be very variable in size. So when this is an outline,
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your transverse sinus tells you you're flush with a tentorium, which you have to be if you want to get to the superior anterior aspect of the CPA.
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If you want to be far enough lateral, you may, very commonly in ENT, our colleague will tell us how important it is to get into the mastoid air cells so you can collapse the sigmoid
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sinus a little bit I mean, we don't want to occlude it, but during the case, we want to do that, but
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ENT is very important on this step, not just to gain that lateral movement, but we get CSF leaks there because we open up the mastoids. So the goal is to have a very open route
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to the CPA in this total axial direction,
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45 degrees within the sagittal plane. And if we can achieve that, that gives us those millimeters that are so important. And if you don't see the superior petrosal vein, you may not be flush
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enough with the Meckles-Kaven, which the superior petrosal vein is a good generalized marker that you're in the territory of that.
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Well, that's great. Frank, do you have anything you want to add to do? Do you open the dura? Where do you open the dura right along the sinus? Because if you do, then you've got to put some
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tacking sutures so that you don't see it. Or do you open the dura and flap it down the other way?
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Well, just going back to the, why do we expose sinus? A couple of reasons If you don't, and you're misjudging. kind of where the sinus is. And if you don't remove an up bone, then we could be
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stirring a cerebellum. And then we have to retract the cerebellum. So if we expose the sinus, then we can make sure that we're beyond that point. So the less retraction of cerebellum, and it's
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easier to get around that. I usually make my incision a couple of millimeter parallel to the sinus It's kind of going along with the sinus, and there are many ways to do it, but I found that way
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it's easier to close. Instead of making a T incision, then when you close, you're coming to this little point. But if you make a curvy linear incision along the sinus, it's a curve, it's easier
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to close. That's just what I found. Okay, terrific. Ed, do you have any thoughts about this from your point of view?
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and My focus area is an anterior stole base, so I don't do any of these cases. That being said, I do have great colleagues who also collaborate with Dr. Sue and the team to gain exposure in this
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area. Okay, terrific. All right, thank you. Go ahead, I'm sorry, Alex. No problem, that was a good discussion. And so this is, you know, some of the collateral anatomy as Dr. Melchasing
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likes to say, looking at some of the bony anatomy, that's in the area again. And then the suboxopetal triangle here with the supreme inferior oblique,
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the rectus capis major
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with some of the structures that are again in the area. This is a little bit more relevant for the far lateral approach, but
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we wanted to include it here just because it's, like I said, collateral anatomy.
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Okay, and then this is a cataveric specimen of that last diagram, and the main point, I think, is this venous structure out here, which Dr. Mukazian has pointed out, is commonly encountered and
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can cause troublesome bleeding during the approach, although it's not probably unnamed vein. Is that right, Dr. Mukazian? We're going to name it. We'll find a name. Okay And then there's the
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sub-oxipital fat pad, which your point was that it's always present. It's encountered and the veins kind of live underneath it. Is that right? Yes. I think there are three things to point out
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here that the occipital artery flanks the superior oblique-capitas muscle. And it's sometimes equivalent to the size of the vertebral artery It's not that much, there's not that much difference in
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their end. And it's easy to cut it. And if you're just making a linear or a sigmoid incision and you're getting down deep,
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you could be full and think that you're in the vertebral. Now, I think most of us have learned that after we've
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taken note of how much that occipital artery can bleed. And the other is in the center of the triangle It's more than just the C1 nerve root dorsal primary arena that's innervating the triangle
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muscles. It's that the vertebral artery is in its horizontal segment there. That's where you get into the vertebral artery.
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And so you can see your incisions
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could fool you when you get into the occipital artery Now for the venus, the venus I pointed out
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But I didn't pay much attention to my dissections on the Venus side. And I began to become very respectful when I was doing the dissection for other people for Bertram procedure, which we did
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publish in the Double AS methodology operative
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book on selective neuroectomies for torticollus. And what I found on the cadaver that I ignored, you can't ignore on a dissection, it's loaded with things all around that area. And I have a
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correct or incorrect view that that's really a heat sink to cool the vertebral artery off as it enters the brain, just like the cavernous sinus, that's where internal carotid artery. So you run
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into bleeding problems here
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that are very manageable. the most incisions and they they pack off but those three points that the vertebral artery is in the triangle this large vein is very consistent it's in the center of that
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triangle and the occipital artery. The fat pad is usually there but on a lean person it may be very very minimal.
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Can you can ask your question can you get me or in the muscular layer here can you get me oriented we're doing on the this is left side I'm looking at. Correct this is a left side so in line you see
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that fine line on the right image yes okay that is midline the head has turned a little bit if you go down to the bottom of that you'll see the semi-spinalis cervicus attaching to C2
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bifid spine the first minus c2. Okay, so you're at c2 there. Yeah. Why aren't you going down so far?
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Oh, this is a cadaver. This is not it. Okay. But so you're just showing us the anatomy at this point, this area, okay.
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As you say, why did I go down so far? That would be too far. Yeah. Okay.
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And then one of the points is just during the approach to avoid going down too far below the mastoid tip where the facial nerve exits to avoid causing a palsy there.
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Okay. This is a
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schematic and semi schematic view of the surgical approach that we were discussing where you try to get basically flat along the petris bone, which requires that you get anteriorly as much as
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possible so that you can access the IAC. Dr. Mukasey makes the point that the IAC is here at a 45 degree angle backwards from the surgical corridor. So it's not at a 90 degree angle. And that is
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an important technical consideration when you are opening it up.
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That's terrific, a better terrific image. And Frank, it makes sense why you're saying that you want to be as close as you can so you don't have to retract a cerebellum
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Exactly. And this is just one of the approach, right? Retro-sick, you could also do trans-lab or middle fossa, but I think we're focused more on the retro-sick point today.
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Would you do a trans-lab or a middle fossa with the size of this this tumor that we saw or? I think middle fossa, we limit to be a little bit smaller case and and and I think it's um operator
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dependent to, depending on your training, the autologist where they train, they have a different approach and school thoughts. But most likely for tumor this size, in our hands, we do retroceic.
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And for a very large tumor that involves the petrias and we, and the patient has no hearing whatsoever we do, we could, we could do translat. I think the Dr. Seuss point and, and Ed may want to
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add to this, the Garcia Abana's procedure, I, I believe was really only for intercannular. It was not for tumors that were intercannular and extended into the cerebellia pontine angle. I may be
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incorrect about that, but that was always my impression.
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I think you could get away with some extension into external to the
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IAC, but if when it gets a little bigger, unless that's how you train to do it, most people would avoid doing the middle fast. Okay, good. Good point. Good diagram too. All right, so then we
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get into kind of the meat of this, looking at the CPA This is a beautiful drawing from Dr. Malkazian showing the cerebellum gently retraction backwards, the 78 complex, setting into the IIC, the
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fifth nerve going into Meckles-Cabum, and then more superiorly, the fourth nerve and the superior cerebellar with the
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tentorium and the greater superficial patrosal knot nerve, that's the superior patrosal vein. And then going forwards, this is kind of a view of that in a cadaver, basically the exact same view
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where you have Dr. Marquesian. kind of pointing out the different frame in here with his, with his instrument that you can see. That's Michael's cadum. Yes. And the IAC is more inferiorly. Yeah.
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IAC
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is down there.
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Okay. And this view shows the
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IAC as well as the IAC as well as the jugular frame and with nine, 10, 11, entering and kind of the angle of the IAC relative to the nerves. This was a catabiric specimen where the brainstem had
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kind of sank a little bit. There are some catabiric changes. So the nerve looks like it's going in this direction, but actually the point is that the IAC is going to open up in this direction. So
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when you're drilling it, you have to kind of open it up, not like that, but more on a posterior angle.
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Okay, very good anatomy, very good. Once you get into the ISE, let's see, this is what you find. Now it doesn't always look pretty like this in there, my understanding, but the facial nerve is
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superior and towards the head, so rostral, the nervous intermedius is small and more inferior, and then the seventh and eighth are also in there more inferiorly with the superior vestibular nerve
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sitting on top of the inferior vestibular nerve. The cochlear nerve, Dr. Melkasean, made the point that it tends to exit the brainstem and then actually wrap around and underneath the seventh
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nerve, so it's not always visible during these approaches, but it's down there right underneath.
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This is a very complex picture, and
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Dr. Hymn said he has worked very hard and selecting. things that will try to tell a story. And I think both of us found it difficult. So I'm going to, for the ENT and people listening, this is a
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view of the internal auditory canal meadus, as if we're sitting on the chrystha transversus,
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and looking out towards the brain stem. That means where it says floc, that's flocular lobe, and where it says CH, PLX,
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that's chorid plexus.
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The importance of that is that when you're at the brain stem, it is a flocular lob yield that sits basically on the root exit entry zone of of seven and eight.
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And the chorae plexus sits on the lower cranellars 9-10-11. So if you're sitting on the crest, the chrysta, looking as if you're in the canal and looking out of the canal towards the
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brainstem, seven ends up
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more anterior and eight vestibular superior and farrier are so variable because they stick together and they don't separate always in the same
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length of the
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vestibular component. And I always found it confusing. And I spent a long time realizing my confusion was never going to be solved, is that the way the eighth cochlear if you look at the
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on the top, you see a red, seven, yellow, nervous, and are medias of Risberg, an eight vestibular, a eight cochlea, that I think the short story is this. If there's a rotation of the nerve,
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it's probably the green dot that moves more rostral
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and that puts it underneath the seventh nerve
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going through the perforations of the inferior
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area below the
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transverse crystal, which we'll show you that on another image. That's a mouthful. I've always struggled over getting the right drawing for this, and I've struggled many times, trying to figure
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out on a cadaver which nerve was there. which I think in the operating room may be easier because of the stimulation. Yeah, you don't wanna hurt seven. And so once you're confident, you know,
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seven, the rest of it is a little bit more relaxing. And yes, if a person can hear, you don't wanna injure cochlear, but I think seven is a devastating injury. Absolutely Frank, any surgical
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tips as to what you encounter, what you do?
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I think this may come later. I think this anatomy is showing the kind of the IEC in its transparent way, but we don't really usually approach like this, right? We come from retrocyc. So the
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first thing we encounter is the cerebellum We have to do some. dissection to release CSF. And so the cerebellum will naturally fall back. And then once we identify the tumor, we stimulate, I
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think this may come a little later, maybe when Alex shows the subsequent steps, then I can maybe make comments there. This is just a great and an anatomical understanding of looking from the
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outside in, but we will never see this view unless you do a trans lab, right? I don't even think you see it there, Frank Yeah,
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you have to imagine that you're sitting on the Chris, maybe we're building and your back is leaning against the builds bar. Right, which is maybe one day it will be possible. Yeah, yeah. Okay,
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Alex.
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Okay, and then this is a diagram of the super-alivary faucet, which is a region that, Dr. Malkasian introduced to me in this area as an important area with a lot of kind of key brainstem nuclei in
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the area that you have to consider when you're operating around here. I think Dr. Malkasian had some things he wanted to say about this area, and so I'll let him. I think we can wait until they do
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the surgery on the schwannoma. Okay, sounds good. So then there's another view of that from the inferior perspective. This is looking up at the
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cerebellum, this is the medulla, those are the pyramids, and then here's the super-alvary faucets on both sides, with the red indicating the more risky areas to manipulate.
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Okay, and then here is just a little bit more collateral anatomy looking really to the most anterior reaches of what you can access through a retro-sig Dr. Mokazian made the point to me that this.
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Black solid line here is beneath Meckles Cave. And so this is Meckles Cave basically opened up so that you see the trigeminal nerve turning into the trigeminal ganglion before splitting off in a B3,
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two and one. And you can access this area through a retrostake if you need to, but it's very hard to get any more anterior. And if you do need to get any more anterior then the best approach is
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probably a different approach or an anterior skull-based approach. Excellent, excellent anatomy picture.
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Okay.
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This is just a
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quick look at cranial nerves nine and 10 where the point is that there's a ligaments that separates them as they go into the jugular frame.
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And let's see if we can find it right there. There it is.
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Obviously, on a cadaver, you can go find a ligament. It's not something that you should do for an operation because we all appreciate that these lower cranial nerves are really rootlets that are
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very open to injury.
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But it does separate 9 from 10 and 11 Okay, so after that very comprehensive view of the anatomy, we can take
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a look at our surgery here. So, this is the beginning of the video when we brought in the microscope for the drill opening. The craniectomy had already been performed. You can see this is our
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C-shaped incision that we tend to make three finger breaths behind the pinna. Superior is here, inferior is here, posterior and anterior And so the patient's head is this is the right-sided
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approach, and the patient's head down to the left, they're in kind of a three quarters prone position
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And so we begin by opening the Dura in that semicircular fashion along the sinus here, I'm tacking it back with neural on, gently dissecting the cerebellum away, and then going in and finding the
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cisterna magna, which is open sharply to drain CSF, which allows the cerebellum to relax. And I should point out Dr. Sue and Dr. Mokaze and Dr. Kwan, if anyone has anything to add or comment or
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if I misrepresent anything, please stop me and jump in.
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So now we're working more towards the CPA, and here you can see the interface between the petristura, the schwannoma, and kind of where the two
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meet right here.
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This is stimulating the surface of the tumor, as Dr. Sue is mentioning, to make sure that there's no upper interfacial nerves placed posteriorly and sizing it. and then beginning our debulking,
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the first step of the tumor resection being to debulch it as much as possible in order to mobilize it and get to the IAC portion. Here you can see the tumor leaving the IAC as it's been debulked
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enough that we can kind of make that out, although it's still a rather invested with tumor. And so the debulking continues. So Frank, can I ask you a question? You don't, you're not using the
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cavitrine at this point Do you do this all without the cavitrine or without, you find it better to do it that way? I find it easier and quicker initially. You'll see the cavitrine is most, I mean,
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we use that a lot. But initially, I think using these, these are called the spacer dissectors. They're sharp edge cups with small, medium, large sizes. And with the angle, you kind of hug the
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capsule, Stay inside the tumor. you want to find that interface and pull the tumor in. And this is a quick way to quickly debug the tumor and then do a frozen section and just kind of gut the tumor
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as much as possible. You can just gravitron this for sure, but I found this a lot quicker and cavitron can be used later to shave the deeper portion towards the brainstem laterally. And
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that's safer that way But this is a quick move to quickly debug the tumor. So the tumor will collapse a little bit that we can find a nerve. Are you worried about pulling on the tumor that would
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pull on the facial nerve or you don't think it's that significant here? No, it is significant. Not depending on the size of the tumor, but if you have a 253 centimeter tumor, there's a lot of
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kind of the meat of the tumor to, And the thing about this dissector is it's sharp. on the edge, so we're not just pushing things around, we're actually sweeping it and using the lateral sharp
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edge to cut the tumor and dissect that plane so we can cave the tumor in. Okay. And in the meantime, we have the facial monitor and going the whole time continuously. With the press probe, we can
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test it, but it's showing EMG activity too. So if you irritated the nerve, we'll stop. Any other monitoring you used, your monitor or any of the other cranial nerves or just facial acoustic,
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whatever else? We use the bear, but if you have no hearing, then we use the contralateral bear. And then also, sometimes we monitor 910 to 11. Okay.
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Okay, terrific. All right. So this is showing a little bit more of that. After it's been debooked, We kind of go to the medial portion and start separating it from
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some of the medial structures here, stimulating to make sure that there's no facial nerve and then separating it away. I think we start to see a nerve in the depths there that I believe is the 11th
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nerve. Dr. Sooten, correct me if I'm wrong about that. And then here's where we bring in the cusia to kind of debulch some of the tumor once we've decided that it's safe and thinning things out
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And again, kind of dissecting the tumor from medial to lateral away from the brainstem before now Dr. Lin, our neuroatologist, jumps in for the IIC opening. So this is incicing the dura around
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the IIC, the petristura, pushing it down to expose the bone, and then he starts to drill. The drilling proceeds Once it's thin enough he feels the actual opening with the
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blunt probe, and then is able to kind of thin down the IAC in an eggshell fashion, superiorly, posteriorly, and inferiorly, until it's very thin and can be removed. This is a diamond drill. Yes,
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the coarse diamonds, yes. Sequentially smaller size. I think you start with a four millimeter and works down to a two millimeter.
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So once that's removed, we can see the IAC, which we stimulated before opening with the beaver blade and then performing some debulking with the kusa, stimulating again to identify the facial nerve
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and peeling the tumor off to the stupider nerve,
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also using the probe to do some dissection. And here I think is the anatomy that we can see here. So the superior vestibular nerve is here, the inferior vestibular is there. Here's the tumor being
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peeled off of it and then the facial nerve is in here. Right, this is This is excellent technique, just super.
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Okay, oh, what happened?
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Okay, sorry. Um, what happens?
36:18
Okay, very good. Sorry about that. No problem, you do have a fight.
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Okay, so then at this point, Dr. Su is further pulling the tumor out of the IAC with sharp dissection. Once that's done, we separate the tumor from the tentorium where it really comes apart quite
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nicely, but then when we go immediately, it's a little bit more adherent to the brainstem, as you can see here, and that's where you have to be careful. So we're dissecting it carefully here off
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the
36:52
cerebellum. Again, mostly using sharp dissection, some bipolar electrocottery, and really just being careful to slowly mobilize the tumor from the surrounding attachments, debulking it, some of
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the capsule in a piecemeal fashion, and just very carefully, sort of removing what we can safely.
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Here we're peeling the tumor away from the brainstem, and then using the probe to make sure that everything is safe as we continue to dissect. I think at this point, we start to realize that this
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last rind of tumor is pretty densely adherence to the brainstem, and maybe going for broken, taking it all would not be the best course of action. And so we just turned our attention back to remove
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this last piece of tumor from the IAC, and then did a multilayer closure
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Which is not shown.
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Here's our post-operative outcome. So you can see the very significant resection with just a small amount of residual here against the pawns, which we decided to leave in order to preserve,
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function, and not cause a big problem. And then post-operatively, she did have a little bit of V3 numbness and mild left facial weakness, which was a house crackman too, but.
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very, very
38:23
not, not a very severe, and I think it's improving over time. So Frank, your goal, major goal is to preserve the facial nerve, because I'm sure in your mind that's a devastating deficit, is
38:35
that right? Yeah, I mean, it's a trade-off, right? I mean, we can make the MRI look perfect, but if she has weak face, it's not worth it So I think, you know, as we learn more about these,
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I would become more conservative actually, you know. I mean, if you talk to some other surgeons who were doing this, say 20 years ago, they would probably take everything out and suffer the
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consequence. But now we know that over time, that's going to collapse down, and if it grows, we can always use radio surgery as an adjunct treatment But most of the time, we watch the low
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residual.
39:18
and try to preserve the facial nerve function. The biology of it's a slow growing tumor. Is that right, Danny? Yes, it's the tumor that starts at the Oberstein-Riddlich zone. That's where glia
39:33
transitions to Schwann. So you have CNS glia meeting with peripheral. And for some reason, there's a vulnerability there. Many people have tried to work out histograms exactly where that will
39:47
occur And it occurs anywhere from just Juxda to these nerves leaving the brain stem to really at the transverse chrysta. And that's why the old studies used polytomograms with air into the
40:04
inter-auditory meadis. And if they saw erosion of the chrysta, they knew there was at least an intra-cannolecular tumor. That was a famous ENT way of studying this There's something I'd like to
40:16
point out. There are two things. It takes a lot of experience and good judgment
40:24
to do a surgery, and you know you're leaving something back
40:28
that you haven't removed the whole thing. I think that takes a lot of strength. I want to point out something here where in my judgment, a very good decision I will talk a little bit more about the
40:45
super-olivary fillet, which means small pit. If you look above the enhancement, that is at the posterior aspect of the middle cerebellar peduncle.
41:01
Where that lesion is is in the most medial part as a cerebellar pontine angle, which is the super-olivary
41:15
that is a very busy area which I want to make a point of. You see where the cranial nerves all come out, you're going to see that they're only about 10 millimeters
41:32
by 10 millimeters in area. And this small pit is probably the busiest area for cranial nerves.
41:47
In the
41:50
whole cerebellapontine angle that we get to have a target that could wipe out all of them like that. And that also includes the lower cranial nerves 9 and 10. So I think it's very hard to leave to
42:03
run back, but when it doesn't fall away, my experience is you hurt the patient. If it just falls away, way, it's fine. But once you start being juxa with the tumor. And the side of the brain
42:16
stem, I don't think that's healthy.
42:21
And at another day, we may be able to differentiate which is safe and which is not when it's stuck to the brain stem. OK. Yeah, and the judgment comes if the tumor is really sticky to the - stuck
42:35
to the brain stem. And then there also some venous structure on the surface of the tumor. You try not to compromise that
42:44
And the other point is when you use a PROS-PRO, we really wanted to pick up the signal from the brain stem side and the IAC side. I mean, it's in continuity. And if we can get that at 005, 01,
43:02
that's a pretty good predictive number that the nerve is going to work well.
43:11
Okay, that's excellent
43:17
Okay, um, while that, that's pretty much that case. I think these are some of the discussion points that we've already touched on. Um, so I don't think we need to go into this too much detail.
43:29
Just a couple of points for the audience. So, uh, you hold off on, on radiation, uh, Frank, until you see recurrence. Is that right? But depending on how much tumor is left, uh, for example,
43:44
if we have this amount of tumor left, we'll get an MRI in three months. And most of the time we see this collapsing consolidation of that little line into a little ball. Uh, and if it's small
43:57
enough, we would watch it. Uh, and then if it grows subsequently, then we'll try to radiate that.
44:07
But if we left a lot of tumor behind and it doesn't, um, it is still taking a lot of space. We could consider the re-operation or radiation. Okay. Excellent.
44:25
All right. Alex, that was an excellent case. So we can get added into this. Do you want to go to the third case or do you want to stop here? It's up to you guys. Yeah, let's see the third case.
44:36
I will skip ahead. And that's good because I think Dr. Mukesh and I wanted to flesh out the anatomy of the far lateral a little bit more
44:44
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