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Grand Rounds-Technical Nuances for Resection of Acoustic Neuromas: Retromastoid and Middle Fossa App

Mustafa Baskaya

April 10, 2015


- Hello ladies and gentlemen, and thank you for joining us for another session of doubleness Operative Grand Rounds. This is part two of our discussion regarding technical analysis for resection of acoustic tumors. Part one covered the translabyrinthine approach. Dr. Mustapha Baskaya from the University of Wisconsin, is our guest today, we're going to cover retromastoid and middle fossa approaches for again, resection of acoustic tumors. Mustafa, thanks again for joining us. And we all are very much looking forward to your great videos covering the technical losses for these routes. Thanks again.

- Thank you, I'd like to thank you and WNS for having me here this is a great pleasure also like to thank my neurotology partners Dr. for teaming up with me in this complex cases, as well as my fellows Dr. Chip and Dr. Lumos for helping me in these presentations and the video editing. As you mentioned, this discussed in the first section, the translabyrinthine approaches and its nuances and the technical points. In the second section, we will discuss the retrosigmoid approach and the middle fossa approach. As you know we know in the first session, we mentioned the advantages of the translabyrinthine approach. One advantage of the translabyrinthine approach is exposing the more lateral part of the brainstem and the structures to the brainstem. In the retrosigmoid approach, we are one step behind and you are as the name tells us is you're behind the sigmoid sinus. So, you're basically dealing with the cerebellum and lots of parts of the cerebellum, but main advantage of retrosigmoid approach on the contrary is the you have chance to preserve the hearing and if hearing preservation is the goal and another advantage is the you have better control of the imperial aspect of the cerebellopontine angle and you have better control to juggler for a man and is shorter exposure time as you know in the best and fastest hands. Translabyrinthine approach will take at least two and half to three hours. And retrosigmoid approach even in the experience chief resident it may take just 45 minutes to 60 minutes. And main disadvantage of to retrosigmoid approach as I said before is much cerebellum is exposed and is there is no dura to cover that part of the cerebellum. And you need to apply some kind of retraction even if there is no self retaining the tractors you apply retraction with your suction or your bipolar forceps and retrosigmoid approach gives it a pool where to control. And it's another problem. Especially this factor is important in the hearing preservation cases. You've tumor extending to do old way to lateral and have the intel canal. You can drill but you may lose the hearing by just drilling the lateral canal. So that's another disadvantage. And there's a higher incidence of postoperative headaches in even after you completely covered the chronic damage defect with the patient's own bone or the cranioplasty. So I will just go over in the first part of the retrosigmoid approach to the positioning. Positioning is similar to do translabyrinthine but you don't use in the trans status since it's a mental approach. And you don't head slightly more than a you will do in the trans lab. It's almost 88 degree and we pay attention again the main things is not extending the chin, flexing the chin too much. And in all rectosigmoid approaches. This is basically hearing preservation surgery. We like to monitor the brainstem auditory potentials, in addition to the facial nerve continuous EMG monitoring and the incision is you can do any way you like to I have no problem with incisions. This is I learned from my ENT colleagues is kind of C shaped post a little incision. It gives you a better chance to flap the skin and kind of exposures I feel is slightly larger than the and the linear incision. This incision this case wasn't for the acoustic neuroma this was for the large sample of an angle meningioma in acoustic neuroma cases I will be a little closer to the ears almost to finger breadth from the external canal. As I mentioned we a elevated flap like we are elevating this cult lab in another craniotomy and we harvest the small piece of two templates facial pre cranium because these surgeries takes several hours at the end you can do the primary dura closure because dura is very dry or you don't have a good dura to close. So this is important to have at the end. So you can do watertight closure. There are so many papers on the on the asterion as a surgical landmark. These are the dry cadaveric dissections from my lab. As you seen every space land you can't really see where are the asterion is. so asterion is not a constant reliable landmark. So, I don't pay attention when I met my sigmoid and transfer sinuses best way is to identifying the inner posture early and the zygomatic process that line connecting both points is going to be super nuchal line and the superior Temporal line. So that to me is the best atomic landmark, but nowadays is using the stealth is almost becoming a routine in every case. So we just confirm that with the stealth and we mapped briefly with the start no navigation or any kind of navigation after demonstrating the transfer sigmoid signs junction. There are different ways of doing the Rectrosigmoid craniotomy or craniotomy, I like to start right behind the transfer sigmoid science junction making a little verbal and then turning the flap the cranial tool and this is the important part. I think during the transfer signal signs junction and the sigmoid sinus. Just getting a glimpse of to the sinuses is important so when you open the doula you can retract the dura better. So your exposure is not limited. Once the craniectomy and craniotomy done as shown here, this is transfer sinus, you're seeing the junction and then we got just a little bit probably 1/4 of sigmoid sinus exposed here. And then we are ready to open the dura and this is the trick better known. Thanks to Dr. Magit Sammy who taught us the acoustic neuroma surgeries. You open if you are part of the cerebellum, dura cerebellum, and you aspirated CSF in spite of mannitol hyperventilation, steroids, there's still some cerebellar swelling, and it may cause inadvertent injuries of the cerebral cortex while you're opening the dura. So in every case I do this before I put the microscope aI go to dura open it and the system you're opening in the natural cerebellar meddlers system. There is a misconception people think we are opening the cisterna magna here what is cisterna magna all the way middle here. Now we go to the video demonstrating the positioning and the important initial steps before we start the surgery. Before positioning the head as shown here we are placing the necessary electro station load monitoring auditory evoked potentials, little shoulder pump in this case, patient is on the heavy side that making sure neck is not too much flex. So we have relaxed neck and I am I am demonstrating the superior nuchal light from zygomatic line and that is confirmed with the start navigation. Then I'm again drawing the line as I mentioned, this is not the acoustic neuroma case. This is just a demonstrate the retrosigmoid approach. In this case, cranial incisions slightly bigger than the two finger breadth which will be the normally the size of the retrosigmoid approach in acoustic neurons. And these are the routine steps and the makings, the sculpt that and elevating it shortly all with Bobby Kotori and this part of the exposure we will obtain temporary spacia or along with the pericranial to use the ad for dura plasti initial girdle is placed right below the transverse sigmoid sinus junction we are turning the craniotomy flap, and during the ball over the transverse sinus first and then junction and the sigmoid sinus. And as you know, vaccine in and vaccine out making sure this is a good point for the residents. Vaccine all the mastery AR cells opening the lower parts of the dura and aspirating the CSF from metal cylinder the modular system and then up to relaxing the cerebellum completely completing the rest have to dura opening you don't have to open all the dura all you need is retro sigmoid part that's all part of the cerebellum. This is the case to demonstrate the intradural surgical technique. This patient was a young female who presented the diminished hearing but her hearing was serviceable level over 80% discrimination score. And we elected to do rectosigmoid approach. The main reason I'm going to mention when I compare rectrosigmoid approach with the middle fossa as you see here, there is that lateral part of the IAC, there's a CSF space. So you don't have to do all the way and that won't cause injury to the inner ear organs. So approach was the retrosigmoid approach.

- May I ask Mustafa, in this patient, why wouldn't you do radio surgery? It's a small tumor, radio surgery has been deemed effective. So can you tell us about the pros and cons of radio surgery versus surgery?

- The pros of the surgery as you know you're eliminated this process if you perform the gross total resection, his patient is basically cured. And you know, also the pathology 100% certainty and of course, your results should be comparable to do radio surgery results in our hands. Tumors less than two centimeter size hearing preservation rate. I just want to emphasize all tumors less than two centimeters not just initial arachnoid tumors, our hearing preservation rate. They're both 50%. I know in the literature, hearing preservation rate after rates stereotactic radiation is 70% or more. But that's the most of the papers published in this is short term for either three, five or six years. There are a couple over 10 years. And very last paper. I'm sorry, very recent paper from Mayo. As you know, initial preservation of the radiation hearing preservation rate was about 80%. And it declines over time and it costs two to 23% at 10 years. And unfortunately there are not many papers in the literature giving the results beyond 10 years. So if patient is young, this is important and vertiginous symptoms are an important part of the symptomatology such as such it wasn't in this case, and the patient and the tumor in our hands. In our experience, we can give a patient comparable results with the radio surgery in terms of hearing preservation. I will recommend surgery. Patient preservation is 100% in this size tumors in our hands over the years time, grade three or better grades.

- I think that these are very correct that as we get more literature coming in with later follow up on reduced surgery we see that hearing preservation may not be as good as once we thought and how's the tumor controlling the long term that remains a question. But I think both of those still don't necessarily justify actually offering surgery to everyone. I still believe that radiosurgery is a very viable, appropriate reasonable option in smaller acoustic tumors even for younger patients, because we do know in 10 years, these tumors are very well controlled with radiosurgery. So I don't want to say that one choice is much better than the other. But there is no doubt there is a surgical recovery time associated with a retro mastoid craniotomy and there's downtime in terms of people being away from work. And so there is no doubt reduced surgery safer than surgery. But again, it remains to be seen, what is the long term outcomes, and we don't really have long term outcomes for surgery either. We know the recurrence rate can be up to 11%. In acoustic tumors at 10 years or more. So there's a lot of questions, but I don't think one can be dogmatic that one can justify or argue convincingly. And it becomes almost a religious conviction for some surgeons, that one approach is better than the other.

- Correct, I completely agree. And I think his treatment recommendations or the treatment in the acoustic trauma in particular should be tailored according to that individual patient. And also, the treating team experience is important. We always consult these patients with neurotology colleagues, as well as the radiation oncology colleagues who does either tomotherapy on denat radiosurgery.

- Alright, well, let's go ahead and review this great video.

- As seen in this approach is done. We are proceeding with the incidental exposure. It's not very sizable tumor, we see this eight nerve complex and the tumor off the origin here is the superior vestibular nerve. This is the cochlear nerve, and I'm taking the superior vestibular nerve and separating it from the from the cochlear nerve initially, on atomically we know that some nerve will be anterior retro to do eight nerve complex here. These are the lower cranial nerves at the lower part of the exposure, this is the top part. After initial separation amputation of two superior let's know or any debulking. Now, we are proceeding with the drilling of the internal acoustic canal. In every retrosigmoid case, we drill the internal acoustic canal open completely to expose as much as possible. So we can do all sorts of resection and we can identify those nerves in the canal, we start with the horse diamond three or four size diamond drill. And as I mentioned in the earlier slides, lateral exposure is important, but if you do very aggressive drilling, especially coming close to the last three four millimeters or two lateral canal, you are risking the hearing. So that should be kept into consideration. And now we identify the nerves in the canal. Here the facial nerve result is gonna be onto the peripheral part of the tumor. We have I just operate the superior vestibular nerve, your facial nerve coming into view more clearly nice lobos nerve and hopefully your nerve comes and the surgical techniques either sharp or blunt dissection but just massaging not rushing and applying too much traction on the nerve, as necessary using the arachnoid knives, performing short dissection last piece of the tumor attach to the a superior vestibular nerve that will be cut and the rest of the tumor will be removed in one piece. In this patient we were able to ignore and the seventh not visible and we were able to preserve the hearing and she woke up with the perfect face and remain perfect. And her hearing preservation was at the virtual preoperative level. You see the gross total risk section in this MRI. This is actually is a good discussion case and I will I like to get your input in this case. This is a 19 year old female who went to a movie theater with her boyfriend and suddenly collapse while watching the movie. And she was taken to locally area where she was found to be in coma. And they call us I was on call just general neurosurgery on call and they said there cerebellar bleed Vita hydrocephalus and they didn't have capability or putting the ventriculostomy and we did all the necessary precautions and a ship her to our center. So this is the initial CAT scan showing the some kind of hemorrhage in the left cerebellar hemisphere. I'm sorry, right cerebellar hemisphere with the mass effect and hydrocephalus. On arrival she was comatose, not localizing and her pupils were dilated, fixed dilated with preserved corneal and the gag reflex. So they replaced the ventriculostomy hyperventilated mannitol. And in 10 minutes after ventriculostomy she start localizing. So the routine will be the making sure this is not a vascular lesion, or are we dealing with the neoplastic lesion that led so we took out to do CT angio since we stabilized her, and this shows a gigantic mess that hemorrhage in the lateral part of the cerebellum. So my question, how would you handle this case, Aaron?

- This is an extremely good question. I appreciate you asking this. I think I will do the ventriculostomy. Just like you mentioned. If she's localizing she's improving, did her pupils come down or she was still fixed and dilate? I assume it came down.

- Pupils came down and then she was localizing bilaterally, but not following comments.

- Okay, what I would do is in this case, I'll go ahead and do an MRI overnight. And then I would plan for surgery first thing in the morning. I just don't feel like we have the eight plus staff during the night. And neither the surgeon is in a complete eight plus state to do such surgery, which obviously this is most likely a CP angle tumor at two or three in the morning. So I will go ahead do an MRI overnight, get her set up for the first case of the day next day.

- That's was our discussion too. And it was late night almost midnight when she came to our attention, and that was one consideration another consideration my chief resonation actually propose was just doing the decompressive craniectomy and draining the blood and getting the biopsy and be prepared for the definitive second and final stage. So he talked to me for this and I agree with that, although my initial assessment since she improved after ventriculostomy and she was safe, just go do the elective surgery next morning. For the reasons you just you just mentioned. And we took her to the decompressive craniectomy and we the compressed blood and took to bone off and pathology was schwannoma. And the next day she was following commands and that that afternoon she was excavated. So we did the MRI and MRI shows a large mass consistent with the some kind of cranial nerve schwannoma in the cerebral appointing angle. And so we talk to her about surgery and since I had a large decompressive craniectomy already perform, I didn't want to do Translat and then question her in detail she mentioned that last few months she noticed a little more dizziness and also hearing loss but she attributed this to the loosened viral infection she had she never sought for medical attention. So that was the reason in this case I chose the rectrosigmoid approach. And she did well we removed the growth totally. She lost the healing completely I wasn't able to preserve the hearing. And I never thought I will be at this size of the tumor. But she has been doing fine and she's almost four years out now with the full function, perfect face and the she's back to work.

- Great result.

- Thank you. Next case is a college student, young female who started having the some diminished hearing and the severe dizziness and walking difficulty. On workup she was found to have this large multi lobe related mass with cystic extension into the canal. So this is important this seems like a CSF but actually cystic part of the tumor with the capsule enhancement. So we discussed the options before she elected to undergo surgical resection although her hearing level was speech discrimination was 50% and the petal audiogram was 50 she want us to try hearing preservation at this size tumors, as I mentioned before is very small chance we will be able to preserve this hearing specially when hearing diminish this size is her hearing is borderline. So we elected to do rectrosigmoid craniotomy to follow her wishes and after initial debulking we are during the interlock canal again we use three or four diamonds and lateral drilling the lateral canal is the problem here. And so, that limit is the exposure of two nerves in the interlocked canal especially little part of it again amputating the nerve of the origin which is in this case superior vestibular nerve and locating the facial nerve with the facial nerve stimulator. And now, we are trying to find the cochlear nerve which is for that I'm having hard time so I leave the canal and I'm going back to this internal segment to follow the facial nerve. It's in these cases, it's sometimes it's you can easily get fooled with the appearance of the tumor. Tumor may look like a nerve. But is the if nerve. It's not stimulating early exposure. And if you have any suspicion, so I will not recommend thinking that's a tumor or nerve and just spending a little more time exposing more in the canal. So now I go back and forth. And my mentor dr. Heroes used to say if you make three moves and you're not achieving the goal, you just stop and do something else go other parts of the dissection and come back to that point, later time. That's what I'm doing. And exposing the nerve is nervous very, very splayed. At the poles level, which is the case almost every case. So it's not sprayed. It's hard to say what is nerve what is tumor, but take your time and I discussed these details with her because she was very knowledgeable person and she want us to go ahead with gross total resection if possible. So I nerve is stimulating at the lowest min apolar and I feel good I'll continue but if there is any question I'm going to severe the nerve or I'm going to cause problems. I'll stop here leave a tiny piece of the tumor and follow that serial imaging. So I think that will be your approach tour right Aaron in specially in the retrosigmoid hearing preservation young person.

- I assume or is not coming out. I think this is pretty much what we do. We were very conservative when it gets to the fact that the nerve is adherence. But if the patient is young, what you're doing is making great sense. You're really working on both sides, the cisternal segment, the internal auditory canal the intra canalicular segment and sort of finding the planes as they come to you rather than trying to create planes.

- Facial nerves, preserved. Now that I am getting the last piece of the tumor from the cochlear nerve. Unfortunately, at this part of the surgery, we lost two brainstem auditory evoked potentials. Although I wasn't hopeful preoperatively and I share this with her. So I knew that she's not going to wake up with the good hearing. So she wants to hearing postoperatively which was at the at borderline, but the preserver all the way on atomic we preserved the nerve we lost dysfunction and remaining parts of the tumor is being removed. And she woke up with a nice great one facial weakness but she developed a delayed facial paralysis progress to grade four five while eventually made very good recovery to the great one.

- Yeah, it's almost impossible to save hearing at that size tumor. So I would say that's an excellent result.

- And this shows the gross total resection and this is in the long term follow up.

- Very nice.

- So with that we gonna switch to the middle fossa and middle fossa is the approach be used to middle fossa acoustic neuromas or hearing preservation and tumors either surely into curricula or inter curricula with minimal extension into the system. Main advantage of two middle fossa again, his epidural approach, although you apply retraction to do temporal lobe is actually you are retracting the temporal lobe dura and you expose to superior internal auditory canal very nicely and and you give chance for hearing preservation and very, very small chance of CSF leak. I don't know how many I have done middle fossa I will say several hundreds and all I had only one CSF leak in the middle fossa approach is is much better in terms of CSF leak than the retrosig and the trans lab. Main disadvantage, we neurosurgeons are not very familiar with this anatomy specialty bony anatomy and it's really complex surgical anatomy and you apply some kind of retraction on the temporal lobe and facial nerve function maybe might be less satisfactory than the retrosig and translab in short term but in long term, I think it catches up and then you have a comparable good results. The position is similar to the sub temporal approach and we do for buzzers or other introduced visions slight extension. So allowing the temporal lobe to fall away from the middle fossa and the incision is variable again is I learned this from the anti colleagues I used to do straight incision they prefer very slight question my type of incision and you can use U shape this is just a preference of the surgical team and we elevate the sculpt lab and be harvested large piece of the fascia to reconstruct the middle fossa flow at the end of the resection and the cranial tummies five by five middle fossa craniotomy and making sure it's flush with the middle fossa flow so you have full exposure to middle fossa flow. And we like to do the interlocutrix in the middle fossa cases with the different sides of the diamond burst core sore point. And we like to monitor in every case facial nerve and the brainstem, auditory evoked potentials closures, just simple putting the muscle and aphasia and some kind of fibrin glue sealant and replacing the ball. The main question in the in this part of the talk, maybe you can help me to there are certain cases is very hard to say you will go after making the indication for the surgery is should we do retrosig? Or should we do middle fossa approach? So I'm going to show you two cases. In first case I we prefer rectrosigmoid approach. Second one we did the middle fossa. How do you decide Aaron in your practice when you have same type of tumors small size? And what kind of factors you pay attention?

- This is an extremely good question and controversial. I have to be honest, and I have to tell you that we may rarely ever use middle fossa approach. Because I think the retrosigmoid approach offers you all the advantages you need, such as a middle fossa, but then you just don't retract on the temporal lobe that could be less forgiving than the cerebellar hemisphere. So I would say we have exclusively moved away from middle fossa. And we do like using the retrosigmoid approach.

- It's very good point. Thank you very much. And then I'll tell you what we do, how we approach this question in our daily practice. So, first of all, as you know is the we try to predict the normal of the origin, so is the superior vestibular nerve or inferior vestibular nerve. So as patient we do electrophysiology electronic steganography try to find out which nerve is more effected, which nerve might be the tumor origin, but as you know, is this is not 100%. And then the anatomy makes big difference in the middle fossa versus rectrosigmoid. If the normal of the origin is inferior vestibular nerve and that will create problem with the middle fossa as you know, patient between surgeon and the tumor. So there's a that might be a slightly higher chance of patient problems. And other factors, we pay attention extent of the tumor in the lateral one total of the canal. Here, we know that there's a extension of the tumor is not that far lateral, and we still have the CSF cap and the lateral canal. And we don't need to do the internal acoustic canal in rectrosigmoid approach all the way laterally which itself will risk to the inner ear structures such as cochlea. Let's in this case, maybe slightly even bigger tumor and more cisternal extension about the tumor also extends all the way laterally in the canal. So if we do the retrosigmoid approach, in this case, we know that we need to do more laterally and wider that itself may take the hearing. So in this case, we'll perform the middle fossa just as a couple of anatomical and radiological factors that we take into consideration during the pre op evolution. And this is a very young woman with the small mass in the left interlocked canal came to attention with the ringing in the ear and diminished hearing and also mild dizziness and an outside facility they follow her and her hearing was at a good level very good speech discrimination and more than 90% and that was a correct decision at that time but in follow up they noticed the growth of the tumor and patient becomes more dizzy hearing level is still same same level of hearing. She came to us for second opinion and the we discussed surgical options, retrosig versus middle fossa and they also do stereotactic radiation because of her vertigo and the young age, she chose to go with the surgical resection and we did the middle fossa approach which in this video I will I will demonstrate to you.

- I think that's an excellent choice for a middle fossa approach. And do you unnecessarily taught any other discussions you have before surgery regarding middle fossa versus retrosigmoid?

- With the patient?

- Yes, yes.

- In the middle fossa there another risk is the seizures or the brain damage, venenous injury veinal flabby injury. And these seizures are reported less than 10% in the middle fossa. We haven't had any seizure or seizure disorders of the middle fossa approach. We never had a case we had the brain damage or any kind of intracranial hemorrhage. I tell them to my results and I quote also the literature results I lay out everything and I let them make their own decision in a collective manner. We just showed you initial exposure craniotomy is a quadrangular five by five centimeter craniotomy flush with the middle fossa flow temporalis versus muscles elevated and the important part in the extra drill elevation, we give mannitol. In some heavyset patients, we do even longer drill to relax the brain spatially in the dominant temporal lobe. And other things trick I do opening the dura and aspects in the CSF through the nice dura opening and here is the important point how do you localize the internal canal there are different ways of doing this one is the house method during the warm over the geniculate ganglion and other ones just during the ISC right away, and but the prefer blue lining of the superior semicircular canal in the arcuate eminence and you know as an atomically arcuate eminence and the canal superior semicircular canal and interlock critical as almost 45-60 degree angle relation. So, you this is how we identify the canal in our practice blue lining the superior semicircular canal in the arcuate eminence then finding the IAC using the different sizes to diamond drills and exposing the canal and during the bone the time. I recommend all my young colleagues and the residents going into the lab and studying the temporal lobe anatomy during the temple I'm sorry it's studying the temporal bone anatomy during the temporal bone from superior way middle fossa approach and behind and comparing both in the same bone spacement. so that's very good practice and there are good manuals on that I'm sure your you and your relatives are aware house communicates wonderful manual residence can follow then we are be exposed to dura to posterior fossa and in tight brain this can be a source to drain the CSF tool so little chip softball removed over the canal and this is the poster for the dura and retractor sitting in the petrous reach and leaving the nice ball edge here is important or it's retracted doesn't move and injures the nerve complexes or the brain and cutting the dura over the internal canal and these are all formed by my neurotology colleagues, Dr. Piles and Dr. Gubos. Can I do the middle fossa approach? Yes, of course I can. But I know they will do faster and better than me. So that's how we team up here at the University of Wisconsin. Do you do your own approaches Aaron? Or do you share the cases with your neurotology colleagues?

- We do it exactly like what you're doing, we team up, I think that's the best way to do it.

- Alright, so this is a superior vestibular nerve schwannoma. And don't find the nerves in the canal early is important. As we know, in this case, facial nerve will be posterior to the tumor and superior vestibular nerve comes to the view right away. And my colleague just amputated the superior vestibular nerve at the distal canal. And now he's going to roll the superior vestibular nerve from lateral to the medial direction and then I will come and complete to dura opening and resurrect the rest to do. Facial nerve is located right here. If this was as inferior vestibular nerve schwannoma we will first see the tumor not the facial nerve facial nerve will be I'm sorry, facial nerve will be between the surgeon and the tumor we will be first see the facial nerve not the tumor, sorry, I made a mistake. And we all I open the dura to posture fossa, we see the system. Now, patient just gets to the view right here, partly covered by the dura interlocks the canal. Again, being patient and nicely isolating the nerves again, there's a part of the superior vestibular I realized left behind I am amputating evolving the nerve towards the medial side. Because I don't want to leave anything behind if even this tiny, tiny tumor pieces. So I want to have the full control over the nerves. And that's what I prefer in this case, patient is young patient undergoing surgery. So we should do the full effort to get the gross total resection. And then the rest is again the same same principles here exposure takes some time tumor resection doesn't take too long. But again, tumor is not as big as the cases we do in the retrosig or trans lab. But we need to spend time we shouldn't rush and rushing may cause inadvertent injury to the patient nerve and the copula here is the patient nerve and I think we just got the glimpse of the copula right next to patient nerve. Another important point and we don't like applying the cold irrigation during this the surgeries that drives facial nerve crazy as you as you notice in your shoulders anytime resin irrigates the cold irrigation facial nerves start going off and that really affects surgeon emotionally probably. And then now the facial nerve is here. Last piece of short dissection and the vast tumor is free that will be just sold distal superior vestibular nerve.

- Can you show me the cochlear nerve here please?

- Cochlear nerve is here and it's free now just making sure there is no attachment and see this is the nerve origin spirits renovation nerve and the copula right here and this patient didn't have any changes in the brainstem also evoked potentials or facial nerve stimulated with the most milli throughout the case and she woke up with the perfect face and her own audiogram remained stable, the preserve hearing and she's one year optimum. This shows the gross total resection of the tumor without any remaining tumor and this is also part of the bond. And other case, superior vestibular schwannoma case we perform the middle fossa approach, and this is the case I discussed in the earlier slides. There's a slight extension into the system but it is also extended all the way laterally in the canal. This is a good case for the middle fossa. If this tumor was extending further towards the brainstem. Then I will do the retrosigmoidal approach. And another case small case small tumor 40 year old female and we performed the middle fossa and achieved the gross total resection with the hearing preservation. And if we can go to the video of this case. Again, middle fossa it's important to keep the dura intact in the middle fossa approach acoustics, there was inadvertent injury to the dura here we close it but if you lose the dura, dura is lacerated and you have exposed brain, I think you lose the chance of doing a good middle fossa approach than it will be purely sub temporal retraction. I don't think temporal lobe will tolerate that much retraction and another factor affects the initial exposure. So you can have a bleeding from the superior petrosal sinus. All I recommend is the packing the gel Formoso just as well gel foam powder and here the identify the arcuate eminence we are glue lining the superior semicircular canal and then based on that we will localize our internal orchoiad canal which will have 45 to 60 degree angle with the superior semicircular canal. Important to localize GSPN in early dissection and dissection we prefer as suggested by our master and teachers holster to the anterior direction to avoid the traction injury to the JSP and endogenic with Guardian we densify the superior semicircular canal blue lining and now we are doing the interlocks to canal canal anterior to do superior semicircular canal as you know, all this area if we had chance to see to be concept triangle or quasi quadrangle.

- I assume you're using a lumbar drain here.

- I look at the different factors don't want the temporal lobe, heavyset patients, young full brains will build us longer drill. If not, we just use I just aspirate CSF from draw Tommy I perform mannitol and hyperventilation. And the drilling is actually my I call this is also microsurgery. Microsurgical journaling is art. As you see here, my neurotology colleague is using the drill in a different ways. Using the tip of it using the side of it, I recommend all our residents should spend some time in the lab learning this microsurgical drilling techniques because we neurosurgeons we need to drill too either interior canal or arachnoid process or occipital cold that is taking time one by one and is important to get exposure of the entire intact canal in the middle fossa case. That will give you two full exposure to nerves in the canal also towards the poster fossa. I think we demonstrated this spot now, if you agree we can go to the next next slides or next movie.

- That's a good choice. Let's go ahead and go to part B of this video.

- So this is again briefly to demonstrate we can go to the final part. So we are making Thoreau's on either side of the canal. So almost like in Translab that when we talk about translab We didn't want to sell to degree exposure. This is what he is doing right now. So you really want to expose his will expose to leverage the segment. We don't need to decode the comprehensive relevant segments in the many acoustic neuroma cases is taking time and going slowly but drilling sure. I think is the third part of the video which will demonstrate us to surgical resection of toxic neuro by few. If you wish we can see that.

- Sure, before we go to that I like the way he's using the drill. As you can see, he's using it like a paintbrush, and he doesn't push down. And I want to take a moment since we have this video, maybe Smith some time on that, you'll see that unfortunately, especially with a diamond becomes very blunt people tend to push. And that's when bad things happen. So if you're using the drill the diamond and it doesn't work very well, you have to change the tip. You just don't stop pushing it. And that's what injury happens. And then you really use it very new one. And that lets you like remove in very, very thin layers. Without pushing down. The moment you start pushing down, that's really when it tells you you're doing the wrong thing. And so the other very important technique is you don't have to go all the way down as long as you shell out the bone to the level of the dura then you can take a little caret and take the thin shells of the bone off. That really helps a lot. But as you can see, he really uses proprioception. He doesn't doesn't push down and just go go go go go. He pushed down comes back coop push down comes back and brushes the bone when it's very thin. And that proprioception I think is absolutely critical. It's just not visual, it's visual color, proprioception, experience, anatomy, combined, all of that really makes the use of the drill very effective. And here is that shell of bone you're talking about. So I'll let you take it from here.

- So just show us a few seconds ago the labyrinth segment occupational as you know labyrinth segment the shortest and the Malinois most vulnerable. So once you identify that you move back and you drill the bone to level that you can just peel it the grades or the migration nerve coming back to the poster poster a little bit and opening and peeling the dura opening.

- And again, this is a right sided approach for everyone to be oriented.

- And all the points you just mentioned, are extremely important points when you're using the drills. If the drill is blunt, just change it, don't push it especially when you're doing onto a client process. And then leave a little tiny layer of the bone so you can feel it you don't have to do everything all the way down. Because you can push and cause another injury to any kind of nerve in this case the facial nerve and auto climate process during the optic nerve and the delicate luxury.

- I agree.

- The tumor is exposed is removing the last piece of the arachnoid now I will enter the case and remove the tumor. Tumor is not very big, it's just four or five millimeters. And this part probably takes 10 to 15 minutes, sometimes even very short five millimeter. But again, you have to spend time just don't pull apply traction and rush so you don't hurt the nerves. You see the nerves distally I'm trying to get a sense of where the superior west nerves. And is very small exposure actually is not very and you cannot if you notice I couldn't put micro-scissors tips to cut the nerve. I have to push it. I'm massaging the tumor nicely creating a plane and then necessary times. Just use short dissection. This is the facial nerve. Short dissection creates a plane and then you stop feeling no, here is your nerve.

- Where's the auditory nerve again here Mustafa? Trust when you can.

- Some are here we don't have the clear view of it. And sometimes even it's small tumor you need to debark does tumor can break into multiple pieces and doesn't allow you to handle so just you can just debark to see better and they handle better. Small tumors I actually intercommunicate tumors to me is more difficult tumors that the bigger tumor.

- I will create that special nerve there is that right?

- Here you got to see at the ad clearly all the nerves. Here is the facial nerve and here the auditory nerve.

- So you're dissecting the facial nerve right now.

- Yep, yes.

- So that's auditory that's facial right here?

- Auditory, that's facial nerve. So it's more stuck to facial no than the copula nerve.

- That's very unusual.

- And axon part of the the Spirit cylinder is amputated.

- So no decision and

- We like to put a little muscle piece in the canal and the reconstructed middle fossa flow with the temporalis fascia and the replaceable. And discharge costs of resection of the tumor. And this patient preserved the hearing and and and patient has wonderful patient no outcome. And other small team we're in a 41 year old male each canalicular serviceable hearing

- Let's go ahead and watch the video for this one. I think that's a very nice indication for a middle fossa approach.

- So these are the videos from early times when we had the old microscope, the views are not that clear. Or again look post cricotomy and trying to find this awkward evidence lining the arcuate eminence. This is how we do but there are different ways and whichever way you do it just doing the set monitor bone dissection is important. And once you do that by the semicircular canal, lining the canal and then finding the relationship dispersive silicone canal the IAC of your during the ISD as I mentioned in the talk snap tall, you know this bone density is different from the rest of the wall.

- Do you use steel for ice at all during surgery?

- I use that for everything just to have the backup. Sometimes we have difficult cases, all the variations of the anatomy may be misleading. So even if I don't use it's registered. It's available. And I'm very good point actually, in my experience, start localizes the IEC very well.

- But CT still try to use high resolution CT not MRI.

- High resolution temple CT and even the ticket MRIs. You can see and you can you know you can fuse both images.

- Exactly.

- I don't know all my residence do I appreciate their help so you open the canal dura tumor is readily visible extending the opening of the canal. I apologize for the poor view but this is the I think this is the yes this is a facial nerve and is not easily distinguishable. So I'm creating a plane between patient or the tumor shot by section. As you see, we don't like using CT bipolar coagulation in this small tumors. Any bipolar coagulation closer to the end in the facial nerve or the copula nerves will result in damage of the nerve. So I avoid as much as possible using the bipolar coagulation and if I have to use very very minimal degree. This is distilled into canal I'm gonna amputate that and the world tumor from that sort of immediate direction. Here is the facial nerve come to view soon. Here is auditory nerve and the last piece of to superior vestibular nerve distally. And I'm using very low bipolar coagulation away from copula rotation and updating superior vestibular. Finally, this is the very rare patients in my experience I only two patients will experience improvement of their speech discrimination after surgery usually remain same even if we preserve the hearing or about this patient had a problem when up from 80% to 100% speech discrimination. So it's very last case to demonstrate the difficulties with inferior vestibular schwannomas. So this is again choice of the approach middle fossa and we knew preoperatively we are dealing with the inferior vestibular schwannoma because patient didn't have any dizziness. Any kind of vertigo symptoms and electrons demonstrated to normal findings. Again, quadrangular opening up the middle fossa they are flush with the middle fossa, completely epidural approach, taking time to elevate the temporal lobe dura from middle fossa flow using the facial nerve stimulator to identify the GSPN and if any veins bleeding from the experimental of silence, just packing sometimes dissection can be very difficult in this region. Important to take time and be patient. And once you identify the arcuate eminence and Petrous reach, you can park your retractor here and the hold it the way that petrous reach basically actually be Petrous reach is holding the projector and blue lining the arcuate eminence and spiritual circular canal. I'm not boring you and the audience with the repeating this over and over again.

- No, not at all. I think repetition is really important surgeries probably as important as it can get.

- Vital disappear semicircular canal here and that makes a 45 degree to 60 degree angle the internals canal. As the electrify the laboratory segment early is stimulated, you confirmed that during the rest of the canal. Again, using silence to drill the just painting motions` not pushing, making holes posterior fossa you're elevating the little bond chip over the poster fossa dura and he's opening the dura of the to poster fossa aspirating CSF relaxing the brain and that will help him to gain a little more space here so you can complete the drilling and then you can open the dura. Extending to do opening towards posterior fossa. Here is a server the port angle system and curing the dura over the canal and all we see is the facial nerve now. The tumor entire facial nerve is between us and the tumor. So the viewer the art stated this from the symptomatology and the electrophysiology and when we have this again you need to spend a little more time and be patient and dissecting all aspects of the canal to expose the tumor and move the patient away. So you see the tumor. So anti structure is the facial nerve here. And this is the problem with the inferior vestibular schwannomas. one option is doing the retrosigmoid approach. But as I mentioned, if you do that you have to do the color all the way laterally at that building itself may cause problem hearing. There are nice otology instruments like this one, you can use it for the sweeping motions. Now I am confident I am dealing with the ether rest of the schwannoma. I caught the superior vestibular nerve and the facial nerve is right here bringing the tumor interview more and more. If you do these maneuvers before dissecting the tumor of the facial nerve you will cause undue retraction traction on the nerve and they may have the new suddenly you'll hear the traction potentials in the EMG monitoring and that means you're applying traction and nerves going crazy. I debark some facial nerve here stimulating nicely and other it's this is my experience and this is my theory I don't know if you will agree with this. These small tumors facial nerve is not conditioned so any small maneuver can cause more problem than injury. Whereas in the larger tumors facial nervous condition so long compression from the nerves, I mean you can do more aggressive maneuvers. So I call it the gray conditioning the facial nerve in this case is small schwannomas in the early period you may have even more facial nerve problems than the larger moments. Would you agree with this statement or this is something?

- I completely agree they're more sensitive there for smaller tumors. So I you got to be very very gentle to them there's no doubt about that. And here last piece of the tumor was removed again, muscle plug in the canal and reconstruction of the middle fossa of it the temporal spatial. I'm showing gross total resection. Again, having the different techniques different approaches is good for the treating team and each approach has a role for certain patients. So, I'd like to repeat my statement again being neurosurgeon should be versatile in dealing with this complex lesions because the outcome measures is not like the 1912 Dr. Crosshair was removing the tumor with his finger.

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