Vestibular Schwannoma: Functional Preservation Strategies Free

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- Colleagues and friends, thank you for joining us for another session of the virtual operating room from Neurosurgical Atlas. My name is Aaron Cohen. I welcome you to another session with Dr. Samy Youssef from University of Colorado. Samy is an incredible surgeon. I've watched him many times operate. On his videos, on his courses, really a master surgeon. An honor for me to be working with you along the year, Samy. He's the Vice Chairman of Education at University of Colorado. He's also the director of Skull Base Surgery there. His contribution to special acoustic neuroma surgery has been tremendous. Samy, I'm very honored to have you with me today. I know you're gonna talk about nuance of functional preservation in acoustic neuroma surgery and an extremely important topic. So very much look forward to learning from you and thank you for being with us.

- Oh, thank you, Aaron, for the invitation again, honored to be back and share my thoughts and on my team's work in acoustic neuroma surgery. I'm looking forward to it today.

- Thank you, let's go ahead and jump in.

- Good morning everybody. Thank you, Aaron, for the kind invitation to share some of our topics in your prestigious 3D Atlas. Really it's an honor to be here again, so really appreciate the invitation and let me get started sharing with you my subject today, which is vestibular schwannoma. We actually have a busy practice, myself and the skull base team here in University of Colorado. And so we'll share with you some of our strategies that's all focused around the functional preservation, which is this day and age of vestibular schwannoma practice. So these are my disclosures. None of them is relevant to this talk. And let me get started with just one case presentation, that's a 39 year old, MD, that uses the earphones, bilateral of course, for her online interviews. So she does the virtual patient assessment and she came presented with Class A hearing, mild balance issues and of course, she's very observant, very active, typical Colorado young person. So she got an audiogram, she got an MRI that shows this small lesion. And here in my clinic, and the thought is, okay, what we do next? And would that be the same thought if this patient had this MRI or if she was 65 years old? So before we start thinking of what to do, let me go over the treatment options. So that can be observation of course, with the small tumors, or we can do surgery, or we can do radiosurgery. But before we choose, we have to look also, at the symptomatology, why is this patient in your clinic? And these are the most common presentations of course, hearing loss is the most common where this patient present with. So this is one of my favorite slides that I always show in my presentations. When we think about treatment options for skull-based lesions nowadays we think of cranial nerves. Cranial nerves are like really linked to quality of life because that's how we communicate with our businesses, our families, our friends. So it's really how we interact with our environment, and anything we do should focus on preserving the cranial nerve function. Whether that's strategy, observation, biopsy, radiotherapy, chemo or surgery, whatever preserves those nerves better or best, we should really pursue that. And definitely, there has been a paradigm shift in the skull-based surgery from when I started my training years ago and nowadays. Instead of admiring our radiographic outcomes, now we go to functional outcome analysis and look at how these patients are doing after surgery. So if we take each treatment option one by one, if we pursue observation for this patient, we're really letting the natural history take its course with tumor growth one to two millimeter every year, probably more hearing preservation, no risk of course, either surgical or radiotherapy. And the tumor might not grow if this patient was more than 65 as some data showed. The disadvantages is before the next visit, this patient can lose hearing, especially a young patient. This patient presented those balance issues, or tinnitus, likely that it's not gonna improve with observation, even though tinnitus is one of the resistant ones. It can still progress at older age and we're gonna have to do surveillance MRIs until whenever. If we look at surgery, we use the same three surgical techniques. We might modify some of the steps, but retrosigmoid for any size tumor, hearing preservation for any size tumor, especially the extracanalicular ones, translabyrinthine pretty much for something that will do lost hearing and medium-sized tumors. People can argue that you can do any size tumor with that depending on the anatomy of the petrous and mastoid bone and the sigmoid sinus. Middle fossa for intracanalicular tumors with good 60-70% hearing preservation rate for these intracanalicular tumors. The advantage of surgery of course it that we remove the tumor and if we do gross total resection we have tumor control, 97%. Improvement in symptoms for preserved hearing or if there is trigeminal neuropathy or there's balance issues there, then it is likely to have some better improvement after surgery. Path confirmation. We're gonna stop imaging, at 10 years in my practice, when there is no recurrence. So there is no long-term radiotherapy effect. And like I said, if we preserve hearing, depending on the size of the tumor, of course, there's 12 to 85% among literature, across literature of hearing preservation rates. We'll come to that shortly. This advantage that we all know that there can be temporary cranial nerve palsy like the facial nerve, mostly. Spinal fluid leak, infection, hospital stay three to five days. In my practice like near three days mostly. Now if we do the radiotherapy, which is becoming more and more popular, especially for small tumors, more than 90% tumor control. The claim of less cranial nerve palsies, acute, I agree because you don't manipulate any cranial nerves, so acutely there will be less cranial nerve palsies. No infection, no CSF leak, all the cutting side effects. And if you preserve hearing, like I said I'll come to that shortly, that is higher short-term hearing preservation. The disadvantage that the tumor can still progress, as some literature show that it's up to 15, 20 years, that might be some recurrences. Cranial nerve palsies, they're recorded more on the LINAC than gamma knife, depending on which which reference you read. But it's late during a nerve palsy especially a trigeminal neuropathy. And of course less improvement of symptoms, especially balance. Temporary expansion of the tumor, what we call the acute flare-up phenomenon, six to 12 months, in some reports up to two years even. That we call that the pseudo-progression, or the temporary expansion, or the acute flare-up phenomena that might require intervention at some point, depending on the symptomatology of course. And the radiation induced tumors, I wouldn't take that as something significant but there is like around 56 new tumors secondary to radiation. And that might increase more as we accumulate more experience with that tool. So something to be aware of about the surgical management of vestibular schwannomas after radiation. I'm sure most of our audience here will be aware of that. This is an example for different series, that's reported by Professor Fukushima and his group. And most of these experienced surgeons had some difficulties when they went back for tumor progression after radiation to treat that tumor. And we all know that there will be more adherence deficient nerve, less chance of gross total resection, and higher chance of facial nerve palsy, as you see here. So this is something to be aware of, that if we go, radiate the tumor, that if we come back and treat that surgically, there might be some issues. So when we sit down and go over these options with the patient, we have to be aware of the quality of life. It's not me, the doctor or the surgeon, that's just gonna be part of that assessment of quality of life. Quality of life is 360. It includes the patient as well and the family, and like, that's very patient tailored. So this is an example of the Mayo clinic work about quality of life. That's one of their earlier reports that showed that there is higher quality of life for patients who have gross total resection of their tumors. Because they felt more comfortable that they're treated, they're cured of the tumor. However, later reports from the same institution showed that there are small differences that didn't rise to statistical significance between the different treatment options. But it's more pathology specific and they have more reports to come from over a thousand patients, looking at these fine nuances of quality of life. But overall there is something about the gross total resection that makes these patients feel better. Now if we come to the hearing preservation point with radiation, this is meta-analysis and systematic review that my otology partners and Gubbels did few years ago. And he looked at everything that was published about radiotherapy for acoustic neuromas. So if you look at hearing preservation rate here, that's 73%, at less than two years, okay? So when we tell the patient 70%, we mean two years because it's gonna drop to 59%, two to five years follow up, 48% at five to 10 years, then more than 10 years hearing keeps declining. So if you look at this curve here, everything goes down. Everything that we're doing, radiosurgery, radiotherapy- I mean it keeps going down. So hearing preservation with radiosurgery is short term. Now when I was visiting Jean Regis and his group in Marseille, earlier this winter, they have really one of the busiest centers in gamma knife and one of the most successful practice in treating acoustic neuromas, and mostly with gamma knife. So they have 59.4%, 6.7 years. So that's the average follow up. But they also apply something different, of low marginal dose and under treat the cochlear. So the cochlear should not get anything more than four to five grades. So if we look at that with our surgical principles, we don't like to under treat, so we go and take the tumor from the fundus. And that probably contributes to higher risk of hearing loss. So something to keep in mind, these nuances of different treatment options. So the long-term hearing preservation, and that's in that conclusion, one of the most successful radiosurgery centers, remains one of the main issues after SRS. Something to keep in mind and to share with the patients. On the surgical arm, this also, with a systematic review of meta-analysis done, by Isaac Yang from UCLA. And he looked at hearing preservation with the different approaches. So, intracanalicular 57%, small, which will mean up to plus 2, zero to 20 millimeters. So there's the sternal diameter up to that can be plus 3 even, with that diameter, 37%. Then large 12%. So this is the conclusion of that. So on the surgical arm, these are the results. Problem also is the short term follow up. So when we compare different treatment options, we're comparing apple to orange basically. So what's our institutional trend, or strategies here when we treat acoustic neuromas? When we sit down in the skull base conference and we look at this, we tend to observe asymptomatic patients. However young patients with excellent hearing like that lady that I started my presentation with, we might tend to offer hearing preservation surgery for those. Of course symptomatic tumors at that age group, we tend to offer intervention. And most of our intervention will be surgical. For more than 60 asymptomatic still observation until progression. Then we jump to, or we switch, to the intervention, active intervention. And we can consider radiation or surgery. And we counsel the patient back to our quality of life slide. What this patient would prefer and long-term goals and objectives. And we put the data all clear as I reviewed it with you. Large tumors, mass effect on the CP angle, brain stem, middle cerebellar peduncle, we offer surgery, we do not radiate those. So gross total resection is usually our ideal goal, but neuro preservation is the goal as well. So unless the tumor is adherent to the facial nerve, like that, we have to compromise and leave something minimum on the nerve to preserve the facial nerve. But, our goal is not to leave nodular enhancement. So linear enhancement is okay, how do you know that intraoperative? This is the house clinic model of gross total versus near total, subtotal and partial, and it goes by percentage. My reservation again is the percentage is 2% of a one centimeter tumor is not 2% of five centimeter tumor. So I applied the Mayo Clinic a model of how to have near total resection and five by five by two millimeter they measured that intraoperative on the facial nerve. And the goal is to have a linear enhancement because when you have another enhancement, this is a case that I treated that was done somewhere else and they left this, and after radiation the tumor progressed to that. So as the authors concluded here, that they don't go in with the goal of partial resection and radiosurgery. So they made that clear, like that strategy of debulking and radiosurgery is not their strategy. And we echo that as well, because residual tumor progression can be problematic. So intraoperative impression, that's the issue here. That we're gonna build or we're gonna base our decision, how much tumor or if we're gonna leave tumor on the nerve, that's usually until the day of, or the moment of tumor resection. So is there a way we can be prepared for these tumors before going in? Usually the decision comes with really years of practice and trial and error and experience that you stop before hurting that nerve, before losing the signal or the stimulation of that nerve. And usually the intraoperative difficulties with these tumors in general, in general with any tumor but also with acoustic neuromas, tumor consistency, firm, vascular, adherent, big tumor. Difficult, these are difficult. But it'll help if we really can counsel these patients upfront and have a preset management plan. That okay your tumor is gonna be difficult, we are gonna leave something behind, I can tell, I can see it. But not every large tumor is difficult, we know that. So here's our work, this is where we get the radiographic nuances to factor in our decision. The intraoperative scenarios prediction, how can we predict that? Few years ago we did that study looking at the ADC map on MRI for these tumors. There was some work done before but never proven any value, in predicting the intraoperative difficulty, in terms of tumor adherence, or consistency, or vascularity that you can see of course on the on the MRI. But this adherence and consistency, firm, soft, cannot be predicted to accuracy with the MRI. So we did the ADC and we were able to separate three values using the regression tree analysis. And we found that the middle value here, of this ADC was associated with worse House-Brackmann score on these patients. Not correlated with adherence or consistency. Like, this value we could not have direct association, but at least the facial nerve would function was a predictor of that. And there is higher score, lower score, that were not associated with bad outcomes. And we attribute that to heterogeneity of the tumor, cystic internal degeneration that gave us these ADC values. So we found the correlation and we published that. Now we take that further because in the previous study we looked at point analysis of the ADC point of interest and linear tumor measurement. So in the new study that we're about to publish, we looked at the entire tumor histogram as you see here. So not just point of interest, the entire tumor. And we did volumetric assessment using the regression tree analysis and interestingly the same, the intermediate group of the ADC value, correlated those worse facial nerve outcomes. The range and the cutoffs were a little different, but this is really exciting news because now if we do ADC on these tumors, we can really have a prediction of difficulty, intraoperative difficulty. And we can tell these patients upfront, you know what this tumor, we're most likely gonna leave something and observe it, and radiate it, but we're gonna try to do the linear residual. So near total if we can. And it helps going in with that mindset, rather than waiting until we lose the signal and I said oh, now we have to stop. So that's something to keep in mind and we're gonna publish that soon. Now another way of really preserving the facial nerve during surgery, especially with this large tumors, we did the DTI and we're correlating that with the intratumoral stimulation. So when I start debulking tumor, I stimulate with the brass probe through the tumor and I use supra maximum threshold and start going down. And we're trying to find the correlation between like the orthogonal distance from the facial nerve and the stimulus threshold. And in this way, in the future, if we establish that algorithm we might be able to map the facial nerve through the tumor without doing DTI, which is of course, you know some time consuming, but that's something also that we apply, you see in the videos coming in this presentation, how we do that. Balance function. So we talked about healing, talked about facial nerve balance function. We also noticed in some large tumors that these people require longer rehab for their balance. And we looked back at these tumors. So they're all the grade four, who's grading four, large tumors, compressing the pons and the middle cerebellar peduncle. But we also found interestingly that this patient, some of these patients have the edema in the middle cerebellar peduncle. So we started looking back at those patients, and grade three, four, and we called it the four plus where we found that edema. And we know that the middle cerebellar peduncle is the main balance bundle, the cortico-ponto-cerebellar tract, that's the main balance tract in our CNS. So if the middle cerebellar peduncle, and it was shown the malignant diseases, or vascular problems, that there was some balance dysfunction. So when we looked at these patients and we separated them into four and four plus, based on that edema, we found really strong correlation as you see from the 'P-value' here, that people that had middle cerebellar peduncle, or brain stem, or both, edema, had longer balance rehab and required some some therapy. So based on that we modified the grading system, we added edema as a predictor, or as a grade five. So instead of those grading, we have a modified grading system now. And we also took the measurements, the less than three and more than three centimeter, because also tumor size is relative to the posterior fossa anatomy. Some posterior fossas are crowded, the two centimeter might give you plus four and three centimeter might give you plus three or two based on the- Three mostly. On the posterior fossa anatomy. So the sizes are relative. So this is our modified grading system that we recently published and we presented also in the vestibular schwannoma meeting in Norway. Something to consider if you see that edema upfront, then counseling the patient that, okay you'll probably require vestibular therapy. We could not associate that with the vestibular dysfunction but balance dysfunction. Just to be clear about this point. Now from radiographic nuances to preserve and improve quality of life, to surgical nuances, is there anything we can do better in surgery? I'll start with the small to medium sized tumors because these are the area, this is the area of gray zone. People tend to radiate those and as I mentioned earlier, that's not probably an ideal, or like the absolutely best therapy. So let's see what we can do about these tumors. When you have a small tumor who's intact hearing and facial nerve function, then your goal is to preserve these functions. Some techniques that just by practice and long- Maybe larger number of cases of vestibular schwannoma that I started looking at closer, is to preserve the vestibular nerve and keep it as a buffer between us and the facial and the cochlear nerve. Knowing that it's a schwannoma. So schwannoma is not a neurofriboma, schwannoma is eccentric, as this Mayo Clinic illustration here, eccentric to the nerve. So if we can enucleate this tumor from the nerve and keep it intact, that can help with the dissection plane. So the technique is to start at the lower pole of the tumor, with here, identify the cochlear and the vestibular nerve, and do the sub-perineural sharp dissection, have special tools for that I'll show later, to establish that plane here. And that can also do vascular preservation of both facial and cochlear nerves, by preserving that nerve. And based on our intraoperative findings of this small to medium sized tumor, we identified three types of tumors, based on the topographic relationship of tumor to nerve, or nerves to tumor. Luckily the type one, which is anatomical, so both nerves are going straight from the pons brainstem to the internal auditory canal. That's the most common type, And that is more favorable because you can preserve the vestibular nerve between you and the facial the cochlear. Type two is still favorable, but less than type one, where the tumor is on top of these two nerves and the two nerves are pushed down. Type three that's the most challenging, that's the worst. Because the facial nerve on top, the cochlear nerve at the bottom. And in this case it's very hard to find the vestibular nerve is still intact, 'cause it's all stretched like this. And you're gonna end up dissecting directly on facial or cochlear nerve. And the choice is okay, which nerve you gonna preserve more. So to show that in a video here, so this is the case that had class A, about to be hearing bilaterally. Unfortunately here, one of them is related to tumor and here is intraoperative retrosigmoid approach. So this is a retrosigmoid. All of this technique is retrosigmoid. We do it for translab, for cochlear implant nowadays. So he is preserving that vessel, because I'm preserving hearing, I don't know if it's labyrinthine or not, it's more superficial. But anyway, preserve vessels on the way in. Tumor debulking as you see here. And now I'm gonna start finding the plane. This is the cochlear nerve, the vestibular nerve is here. Superior vestibular nerve. And using this sharp needle dissector, developed specifically for this, it separates the tumor from the vestibular nerve of origin. You see that sharp dissection here. This is a side-angled dissector, semi sharp, that you see peeling the tumor off. And now you can see the cochlear nerve, the superior vestibular nerve here. And debulk. You can argue that you might open the IAC before you do this. Either way. Sometimes we do that, we open the IAC first before we do any of this. But if you have the vestibular cochlear nerves clear like this, for that size tumor, then you can go either way. So now doing the same sharp dissection technique and stay in that plane. And of course the nerve, the vestibular nerve, is gonna be thinned out more and more towards the IAC. But it's not impossible to keep that plane. So when the dissection is done like this on the vestibular nerve, now the facial nerve started showing through the thinned out vestibular nerve fibers. Now operculum is equivalent, there is the superficial landmark for the endolymphatic apparatus. So you have to stay medial to that to preserve hearing. So that's one of the things that we identify. Then this is my neurotologist doing the IAC drilling, then opening the dura of the IAC. And this is one of the tricks that I use. This side-angled, moving the tumor from side to side, rather than from fundus to medially. And when that tumor is bulked like this from medial to lateral, which is the ideal, also is not as nice as when you disconnected like this. So when you do this, this connection here, there is some vestibular nerve fibers still intact. I'm looking for the facial nerve. And this is, as you see, this is type one at the top corner of that video. So the nerves are still anatomical here. And now things start to get clear. Superior vestibular nerve facial, inferior vestibular nerve. You see where the tumor came from? And the cochlear nerve. Very nice anatomy in the IAC. And now this peeling is happening on the vestibular nerves. So the facial nerve and the cochlear nerve are protected. Now that we cleared the fundus, you can do this in any direction you want, because, again, it's on the vestibular nerve. So you're not pulling or causing any traction injury on the fascicles here in the fundus. And now this is connecting the dots, as I say, getting the tumor completely out, waxing the fundus, ear cells. And we actually put an endoscope here. This video might not be showing, but maybe in the next one. We put an angle, the endoscope, this is the muscle graft, reconstructing the IAC with that muscle graft and we put between two layers of Surgicel. So waxing, muscle graft, Surgicel and that will be a closure, gross total resection. Okay, so this is another video, but for type two. So if the tumor is on top of the facial and the vestibular cochlear nerves. There's another example of that, another tumor and Koos 2, this is the retrosigmoid. Just anatomical illustration. So same technique, debulking first. These micro cottonoids are super, super helpful in this nerve preservation technique. So here is the trigeminal nerve. So now you'll see tumor is on top. And now the facial and vestibular cochlear nerves are at the bottom of the tumor. So that adds a little bit of surgical challenge, but not as difficult as type three, I will show shortly. Debulk the tumor, be aware of when to start dissecting the plane, looking for the facial nerve, because it can be crossing up here. And sometimes I use sometimes I just use sharp scissors like this. And now as soon as I start seeing the nerves, here you see that, it's almost like the art illustration of that indentation of the vestibular nerve. And here the facial nerve is very clear, unlike the previous case. Same like the drilling of the IAC. And side-angled dissectors. I cannot emphasize enough that the sharp needle dissectors that I have in my set, and basically keep looking for the nerves in the IAC. So here is the vestibular nerve where the tumor was and sharp dissection to get that off. Then again gross total resection. So these are small size tumors, that are favorable either way, but when you do surgery as I mentioned and you preserve function, we're done. That's something for there to stay. So when we looked at our small series using this technique of vestibular nerve preservation, here is our hearing outcomes. We stayed at A or B in 70% of the cases, and we lost hearing in 30%. So if you look at compared to what's reported globally, we still have really higher, much higher, chance of hitting preservation. And of course our House-Brackmann grade one and a hundred percent. So we published this technique, it's a smaller series now we're looking at larger series. And we're still around the 69% hitting preservation in House-Brackmann one. Something we really feel very strongly about. Now is that only for small tumors? Here is two difficulties, then I'm gonna just show, this is a recent case. This is what we call the modified five. So it's a large tumor, about three centimeter and it's causing this middle cerebellar peduncle edema. Class A hearing. So this is somebody that hears very well and has presented with balance problems and hearing is excellent. So we are going in for hearing preservation even with this large size tumor. And this will show shortly that when we get in we don't really see any nerves. So here is the, through tumor stimulation using the brass probe to identify where the facial nerve is before we even get to the brain stem. And using these micro cottonoids, very important asset, we start peeling the tumor up and there is a way of identifying that vestibular nerve at the brain stem with these large sized tumors. There's always abnormal vessels and that grayish nerve starts to show. Starting at the lower part of the tumor. And here's your vestibular and the cochlear, lower cranial nerves. Cochlear nerve is really very nicely showing here. And no dissection whatsoever on that nerve. I'm here looking for that plane, looking for the vestibular nerve. And you see that pinkish, rose layer, abnormal vessels? That's the tumor nerve, that's the beginning. That's actually that vestibular, not seven. Looking for that plane. And it's usually very, very thin membrane that you see sharp dissection here, to try to find that plane and use it to protect the nerves between the facial and the cochlear nerve. Try to find the vestibular nerve and keep it on those nerves. Scissors, no blunt dissection. Preserving that nerve. Then try to connect the dots again and try to find the lower edge of the vestibular nerve. And as soon as you see nerve fibers, you put the micro cottonoids. It keeps them moist and minimizes your traction because I can put some counter traction, like here with the suction tip, and use these angled dissectors. Here, you see that? That's the vestibular nerve here. Right there. So as soon as I establish that plane, put the micro cottonoids. And this is type three, the facial nerve on top, the cochlear nerve at the bottom. Here. So this is what we have in this case, which adds more difficulty to the functional preservation. Drilling the IAC. Again finding those planes in the IAC. And the IAC is more anatomical of course, then vestibular nerve is preserved here. Facial nerve you'll see through on top. And that's the rose color tumor nerve. Nice plane right there. That's the facial nerve under, the vestibular nerve fibers on top of that. Then pulling from medial to lateral. And side to side. Then hemostasis, thin layers of Surgicel. Gross total resection, and class B. Class A to B at the higher frequency, so she got more of high frequency hearing loss, but still at really good class B hearing, which is still serviceable hearing. So that's really a good outcome with the good word recognition and serviceable hearing for this size tumor, grade five. So that's the post-op, showing the post-op, pre-op, and the change in hearing. She had high frequency hearing loss before surgery, got more after surgery but still, you know like in that class A to B. Okay, so we talked about hearing, facial nerve. There is a really neglected function of the nervous intermediates which is the thin nerve, the runs with the facial nerve and usually people overlook the nervous intermediates. And I didn't have issues with the nervous intermediates when I lived in Florida because of the hot humid weather. But here in Colorado with the dry weather, people really experienced the dry eye so significantly, even normal person would move to Colorado and start using eyedrops all the time. So, chapsticks and eyedrops because of the dry weather. So we started looking at that function more closer, in the patients here. And just a brief anatomy about the nervous intermediates as this was described earlier, as a nerve bundle by Heinrich Wrisberg, if I mentioned his name correctly, or pronounce his name correctly. It carries three different kinds of sensations. Parasympathetic, to lacrimal and salivary gland. So that's autonomic. Taste that's specific, to the anterior two thirds of the tongue. And sensory to the external auditory canal, nose and concha. So people would come and complain of metallic taste for the anterior third of the tongue, if that was dysfunctional, or dry eye of course. Rarely that somebody will will complain of xerostomia. This is an illustration from Aaron's paper here, very nice 3D anatomy. And it shows the three to five nerve roots for the nervous intermediates here between, comes from the ventral pons and it's between the facial and the superior vestibular here. In Professor Rhotons papers that it was even 20% unidentifiable in some aspects. So it's a very hard nerve to see, even in normal anatomy, but with a tumor you can imagine. That is something that would be more challenging. There is a way in some reports, like from Jackler's paper here, that you can stimulate the nervous intermediates and confirm it's an anatomical structure. Has different latency and lower amplitude and it's usually in the- So that's electrophysiologic stimulation, usually in the orbicularis oris only. So when you stimulate it at these parameters and at the 0.4 volt and you get these responses, it's usually in the orbicularis oris. So your neuromonitoring person will tell you that's oris only. It's something to consider looking for it intraop. But when we looked for the function of the nervous intermediates and how people looked at that in acoustic neuroma, I found only nine articles. Only five of them were outcome assessment. I looked at that last night. I found that also these numbers are still valid. That outcome assessment were only five articles. And crocodile tears are the excessive lacrimation from like some of them are synkinesis, 44%. Dry eye, 72%, pretty high. Taste abnormality. And the sensory loss to the external auditory canal was really not that reported. And it's reported with variable recovery so nobody knows how long it recovers for. That's on the surgery side. On the gamma knife side, it's still there, there is 18% pre-treatment. So people can present with that, or if you ask them in the history taking, you can find that they have nervous intermediate dysfunction without even intervention. And it was 22% post-treatment. This is a paper that compared the different treatment options and the incidence of that. In our study, so we looked at 199 patients, more than 50% of that responded to our assessment. And our mean follow-up was 25.8 months. Excessive lacrimation was not a problem in our series, but dry eye was a significant problem, as you see here. And it was more on the surgery side. As expected. Taste was still there, 38% on the surgery side. So it was significant. But at the end of the first year there was significant improvement in taste, not as much as in dry eye. So dry eye was something that took longer and stayed in decent number of patients, I would say 50% that stayed. But taste improved. So that's something to also be aware of and talk to the patients about. Also one observation that we noticed, that most of the responders to our retrospective assessment were on the radiosurgery or combined side and our analysis, or our conclusion, or explanation for that is people who had surgery and got their tumors out were less compliant with follow up because they felt they're done. People who had the tumor still and had radiation were still concerned and they came for follow up and longer term. Also tumor volume, of course, on surgery, you tend to do surgery for larger tumor volume. So I would think that you would think that it's not fair to compare surgery to radiation for nervous intermediate dysfunction because the tumor is larger. But this is something also to be aware of when you look at these results. So you have to take them with some caution. So is there a downside to preserving the vestibular nerve? So basically when we have a good vestibular nerve and we take down the tumor nerve, so that at the end when we clear the tumor, we cut the vestibular nerve. But if you have a good vestibular nerve there, I just leave it and there was association, or not level one evidence I would say, you know, that if you leave the nerve behind you would get balance problems or recurrence. We have not seen that so far but maybe we need long-term follow-up. There was no delay in balance rehabilitation when we left the nerve. These are smaller tumors. When we left the nerve behind. And of course we need longer term follow up for recurrence. This is the case that I presented initially when we did the surgery. She still has class A hearing, but four years later, look this is very interesting that we did the vestibular neurography and right left side are identical. So this patient had excellent vestibular function on the side of tumor preserving the vestibular, one of the two vestibular nerves. So that made me greedy that now I want to preserve every vestibular nerve if I can. Why not if this there is a small tumor like this one here. So this is a small tumor, presented with partial hearing loss and you know some balance issues. And he wanted the tumor out. So middle fossa, this was intracanalicular tumor, we did middle fossa on this and usually these tumors are coming from the inferior vestibular nerve. So when you're coming from the top of the IAC like here, facial nerve will be interior, superior vestibular nerve on top, tumor, the inferior vestibular nerve and the cochlear nerve you almost never see until the end. So here I'm opening the dura, keeping the dura intact on the facial nerve. This is the vestibular nerve and it's just so nice of a nerve to cut. So I decided to work under it and preserve it. And usually the classical approach is to cut the nerve and just go to the tumor. So using these angled instruments, establishing a plane between the normal nerve and the tumor nerve. So this angled, like a ball dissector, undermining that and freeing that nerve completely. Now switch to sharp dissectors, to get the tumor from the inferior vestibular nerve. So here you see enucleating the tumor getting those- It's a small tumor to begin with. These are down-angled curettes that allow me to do this and has blunt top to the nerve, so it doesn't really hurt that nerve. And the sharp cup of that curette will get more tumor dissection from the inferior nerve. Back to the angled sharp dissectors. And now the side-angle dissector, one of my favorites to dissect along the cranial nerves. Freeing that tumor, and now the tumor is free. As soon as you see that lateral part of the tumor, the cochlear nerve is here, remember? So this is between the superior and inferior vestibular nerve. The facial nerve is up here and getting that last piece of tumor off, when you see it coming from the fundus like this. Now you see superior vestibular nerve, AICA, nervous intermedius is here, the facial nerve. And the fascicle from the inferior vestibular, superior vestibular is intact. So we preserve the superior and here is the inferior vestibular nerve where the tumor came from. And that's something that we really don't know, if this will preserve the vestibular function or not on this patient, but, remains to be seen. When we did the six months VNR the vestibular nerve functions were not really as pristine on this side but we're gonna do long term and see how we go with that. So to close this, this presentation plus also with the closure we pay attention to that. We don't use any titanium in our cases, we switched completely to the bone cement. And that's the hydroxyapatite. We use it for translab. We use it for, so here it is, translab, you see the fat graft, then the bone cement. And we believe that it keeps, when it dries up like this, it keeps the fat graft in place and it decreases CSF leak. But not to be arbitrary, we just went and looked at the outcomes of that. We found that patient had better functional and cosmetic outcome with using the bone cement. And we did not any have any higher risk or chance of infection in our patients using that. Because there was some association between using the bone cement and the infection rate. But we proved that it's not higher by any chance and it had better cosmetic and functional outcomes for this patient. So this is something not to leave without discussion, the functional outcome and including your closing technique. So in conclusion, vestibular schwannoma surgery, there are key elements for successful, functional preservation here. Understanding anatomy very well, training and training and training and doing more cases. You learn from every case. Case by case you draw conclusions and you learn something. If you keep improving your technology there is no cap, there is no limit to how much improvement. And technology is, you know, technology is fluid. Every day there is something new. Try to incorporate this in your practice. Adapt your surgical tools and like you saw, this angled dissectors and something so simple as the micro curettes sorry, the micro cottonoids. These really changed my practice in microsurgery and functional preservation. They're so gentle on the nerves I can use them to do the counter traction during the dissection, using all these adapted tools. The sharp needle dissectors, the side dissectors, the curettes, these ball dissectors as you saw in the movies. These are really great assets to successful microsurgery. And in vestibular neuro vestibular schwannoma surgery, they're very, very useful for functional preservation. And to this I'll come to the conclusion of my talk. Thank you for attention and again, thank you Aaron, yourself and your team, that are really, really contributing an amazing asset, such as the 3D Atlas for education. Not just in the US but globally. Thank you so much.

- Samy, thanks for a very worthy lecture. Great pearls. Really a state of the art for acoustic neuroma surgery, where the priority is functional preservation. I think we have been in a spectrum of many changes in evolution of acoustic neuroma surgery. I would say that acoustic neuroma surgery almost reflects the evolution of microsurgical techniques. When we started with, you know, saving lives and using the fingers for enucleation of the tumor. And as through the time of Cushing, the techniques evolved and made that safer. And then eventually Dandy and his techniques of, again, saving life, not necessarily focusing on function. Because we couldn't really diagnose these tumors early on, or effectively. And throughout the years we focused more and more safety of lifesaving procedures. Up to the past 30 years, we have where we have focused truly on functional preservation. Of not only the face, but as you beautifully illustrated, of preserving hearing. And that's really an incredible feat and something all of us neurosurgeons should be proud of. I wanna ask you two questions that I struggle with. Number one, you have a 32 year old executive walks in your office, they have a small acoustic neuroma, still serviceable hearing. Their hearing is very important to them. What would you offer? Would you offer them radiosurgery? Knowing that their hearing would go away as you well mentioned. Or would you offer a surgery, knowing that there's still a chance you're gonna lose the hearing? But there is a very controversial chance you can save hearing in long term. How would you counsel that patient?

- So thank you for the question. That's how I started my talk with the physician in thirties.

- Right.

- And this is something that we really have a long discussion with the patient. 32 years old, we know that the tumor is growing, or it will grow.

- Right.

- As opposed to 65 that we can observe. So we sat down as a team, the skull base team and we discuss this after we run all the facts with the patient about hearing preservation chance and what we can offer with every treatment tool. I went over the statistics of radiosurgery versus surgery. And quality of life of this patient is what matters at the end. What he or she wants to pursue in light of all these facts. And in light of the other ear, of course, you know another hearing ear. We say as an institution when we have excellent hearing, somebody young like this, we lean more towards surgery. And I argue with our European colleagues that argue with me when I present this data and I say that that should be- You take a benign tumor that's curable and convert it into a chronic disease that will be lifelong follow up, by doing radiation for example. But patients are part of that decision. And if they really, really get all the facts together and understand exactly the counseling, they'll say, you know, yeah, I wanna take my chance. If your chances of hearing preservation we say 30 something to 70% in our series, then I wanna try that. Our also backup plan, which you know, nowadays the cochlear implant, if we preserve the cochlear nerve, is something to consider as well. We also go over the data about the cochlear implant, our otology team, but sometimes they wanna wait six months and see another MRI. And that gives them a chance to digest all the facts and do their research and come back in the six months follow up hearing audiogram, MRI. That's usually like a kind of middle of the road decision or direction. But overall our mindset, and when we talk to these people, we go for surgery for somebody that young.

- I know that's the case you initially presented. I wanna go to a little bit more detail. What would you quote them, the functional preservation of hearing in that case, exactly?

- So if it's Koos 2, unless we talk about-

- Yes.

- In light of the surgical outcomes of 37% hearing preservation, I say in our small series and now it's larger a little bit. We have between 60 and 70%. And I say, you know what, let's say 50% chance of hearing preservation. And the advantage of surgery that if we preserve hearing it's there to stay, there's some maybe individual reports that it might decline long term, we have not encountered that. There is no strong evidence that hearing preservation by surgery will decline. So we've been following these people and we do the audiogram yearly and so far we haven't had somebody that declined later on. Some incidents that we had hearing like maybe are intact at the end of the case and in the six week audiogram they don't have hearing. So if it's going to happen, it happens acutely. But long term there is really like a favor on the surgical side that hearing would be preserved longer term.

- There's been- I get that. So let me play devil's advocate. We know the rate of tumor recurrence in these acoustics is not small. Even in the gross total resection MRI scans after surgery. There's up to 10 to 15% chance of tumor recurrence. This is within 10 years of MRIs.

- That was gross total resection?

- I would say- Or let's say gross total at this- These studies are heterogeneous, so I wanna be careful what I say. But let's say 10 to 15% chance of recurrence in large series of good resections after acoustic neuroma surgery. So if you wanna analyze that, there's a reasonable recurrence of these tumors even in the phase of a good resection. Do you agree?

- I disagree with that.

- Okay.

- I do not have that data about tumor recurrence after gross total resection and post 10 years of follow-up of no recurrence, that there will be 10 to 15% chance. I know it's less than a single digit, the chance of recurrence. We talk with our colleagues in busy acoustic neuroma centers and the follow up, I mean in my practice after 10 years no recurrence, pristine MRI, then we stop follow up. But in some centers they do every five years after that because I had one or two incidents of late recurrence and that's in a busy place, like Mayo for example, with acoustic neuroma practice. In our practice I have not encountered that. So I cannot really- I mean I cannot argue or agree with the results. I have to do further maybe digging into that, with what data and what centers? We have to be careful also about interpreting those.

- Right, remember that's a study from clinic, it's 11% recurrence rate. The time period, I don't remember.

- Yeah.

- Unfortunately right here. But I can tell you that the recurrence of these tumors is not small, it's one out of 10 at least. So that's something that I, you know, I struggle with personally. That's an older study, please remember that's not a modern study.

- Yeah.

- So the rate of tumor recurrence could be less. But again you have to take some of these studies with a grain of salt because the surgeon himself, or herself, is evaluating their own results.

- Exactly.

- So that can really confound it. But I just wanna emphasize that no matter how you sort of approach these tumors, the risk of recurrence is real and the patients have to be carefully followed. That's been my understanding. The second question I want to ask you is the issue of two centimeter tumors, I assume you really push for surgery in those cases? These are cases that are sort of on the border and there are patients who are acoustic neuroma patients are very well educated. They have time and they do their research and they come in really well prepared. How do you, let's say consult a patient with a two centimeter acoustic, if they're 50 years old versus 65, 70 years old.

- So 50 nowadays you know that we're approaching that age, or we're in that age group now Aaron. 50 is young.

- Yes.

- Like we consider that young, when I talked about, I talked about 60, 65, even that is young now.

- Yes.

- But 50, healthy, presented with what? What was his presentation, or her presentation as well?

- Dizziness. I'll say dizziness-

- Yeah.

- And like the hearing loss, yeah.

- So excellent hearing, or serviceable hearing, plus A or B. That pushes us more, in also trying to do hearing preservation with this two centimeters. Two centimeters, really that's the category that has the best outcomes.

- Yes.

- Surgically. Balance issues, you can argue about that gray zone of balance with physical therapy. If stimulant therapy didn't improve then you do surgery and say, well if you didn't improve before and doesn't improve after, we have really good experience with that as well, that the balance will eventually get better after surgery. Tinnitus, the study that we did in Tampa as a group and we did also like, systematic review and- And we saw that out of the three options there will be like more improvement in tinnitus on the surgical side or arm, compared to radiosurgery or observation, special observation of course. Slight differences but it was in favor of surgery for this case. So it depends on what the patient's presentation is. But two centimeter, I would say, in my practice, in our University of Colorado Skull Base Team, our vast acoustic neuroma program, we have really the best like surgical outcomes with this. And now some patients come and say, well I want radio surgery. We have that as well. And as you said, they're well educated. They just lean more toward that and I would not talk them out of it. We just, like I said, you know, we honestly present the data. Our data and global data about acoustic neuroma outcomes. And we're like honest with them during the counseling. And as I mentioned in the quality of life also is dictated by case by case by the patient, big part of it.

- I agree. You know, which come brings us to the conclusion we always reach. It depends the expertise of every center. If you go to a place where they have very capable surgeons like you, and they have good results, obviously surgery is many times more indicated. Than a center where they have very capable radio surgeons and not as much people who are interested in pushing the barriers of microsurgery. So it really also depends on the center, as you very well said. It not only depends on the patient, on the tumor, on the symptoms, which are all well taken. And the preference of the patient at the end, but also very much depends on the center. Or those people that really have looked back to their results, have analyzed it carefully. And believe that based on their expertise, what's the best indication for every tumor type? We'll probably never know what is the perfect answer for every patient until the treatment has been given. But we do know that obviously in large tumor, surgery is the way to go. And in the smaller tumor, I think if there is some serviceable hearing, surgery is a reasonable approach, to be able to save the hearing. Because hearing is a very important function. People say, well you got another ear you can hear from. But I can tell you it is very disabling when you don't know where the sound is coming from. When the laterally of the sound is no longer available to you. It is disabling, for especially highly functional people. That is something neurosurgeons unfortunately have never grasped. Because we always treat such high equity, high stake problems that just losing one ear, is just not important in our profession. However, it is important for the patient. So I agree for smaller tumors, if there is serviceable hearing, in good hands, surgery is the best approach. I think in moderate sized tumors as we talked about, is it radiosurgery? Is it resection? Based on the center and in large tumor, obviously, we all believe that resection is the best approach. After all, it's all about patients. Acoustic neuroma surgery is about patients, about understanding your anatomy, and really being able to not force the issue. More important than any other surgery, I would say it's first patience, then technique and then many other things. But if you are a very capable surgeon but you're just not patient, that's one area that you really could compromise things. If you don't take your time and handle the nerve very carefully, it just comes with the territory of these tumors. Acoustic neuroma surgery is like a marathon. Aneurysm surgery or avium surgery is like a sprint. So you've gotta be prepared for the marathon and there are different philosophies involved. I wanna thank you, really very much enjoyed your lecture. Incredible work you're doing, Samy, keep it up. Look forward to seeing you in the near future.

- Same here, well said Aaron, and thank you so much for the invitation. Looking forward to more in the future.

- Same here, thank you. Thank you, Samy.

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