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Grand Rounds-Technical Nuances for Resection of Acoustic Neuromas:  Translabyrinthine Approach

Mustafa Baskaya

March 10, 2015

Transcript

- Hello, ladies and gentlemen, and thank you for joining us for another session of the AANS Operative Grand Rounds. Today's guest is Dr. Mustafa Baskaya from University of Wisconsin. He's the director of skull base surgery there. He is a very talented neurosurgeon who is going to be sharing with us his neuro saw technique for resection of acoustic tumors. The first session would highlight neuro saw techniques for the translabyrinthine approach. And the second section will discuss neuro saw technique for retromastoid and middle fossa routes. Mustafa, thanks for sharing with us those great videos of yours that we're very looking forward to watching today. Please go ahead.

- Thank you, Aaron, thank you for the opportunity. Thank you as well as the American Association of Neurological Surgeons. And I'd like to start thanking my neurotology partners, Dr. Mark Pyle, and Dr. Sam Gubbels. for teaming up in this cases with me. As well as my fellows in preparing this talk, Dr. Ulas Cikla and Dr. Tevfik Yilmaz. First section, we'll start with the translabyrinthine approach. We made significant progress since Dr. Krause described this, it's called the finger technique, almost a hundred years ago. And nowadays we don't just, this is not about the survival. This is about cosmetic measures, cosmetic outcome, including hearing preservation and the facial nerve. And when selecting the approach for acoustic neuromas, there are several factors that play a role, at least in my mind. Level of hearing, depth of the tumor extension into the internal acoustic canal, high jugular bulb, contracted mastoid. This can be very, very limiting factor when you do the translabyrinthine approach. Absent of flow in the contralateral sigmoid sinus, or any kind of anatomical variations in the dural venous sinuses, such as very anterior sigmoid sinus, will be very favorable in the retrosigmoid approach, But it will be very, very unfavorable in the translabyrinthine approach. And experience of your neurosurgeon. We are all very experienced. In my mind, tumor size has no effect on selecting these approach, especially the moderate to large sized tumors between the translab and the retrosigmoid. This is a kind of crowded diagram adapted and modified from the Jackler and Brackmann "Neurotology." I will just, for the sake of time, I will skip that and I will discuss mostly the anatomical factors and the advantage or the disadvantages of the translabyrinthine approach. Translabyrinthine approach is a complex approach. And most often neurosurgeons may not be familiar in contrary to the neurotologists. But nowadays, all neurosurgeons should be familiar with all these skull base approaches, championed by the neurotologist. And we should go to the lab and study this so we can perform it. Translabyrinthine approach has pros on the cons. Main advantage of the translabyrinthine approach, early and positive identification of the facial nerve at the lateral aspect of the internal acoustic canal. This is purely epidural approach. You don't, some small tumor cases, you don't even see cerebellum. You work over the dura, presigmoid dura It provides the complete exposure of the internal acoustic canal. And it provides excellent exposure of the cerebellopontine angle. and I'm sure you are very familiar, because we publish the meta analysis on this subject, has less chance of CSF leak compared to the retro sigmoid approach. Main disadvantage is that you basically, you sacrifice hearing if patient has any serviceable hearing, which we don't do anyway, but that's some smart aspect of it. And some tumors, it may not provide enough exposure, especially the anterior aspect of the tumor. And definitely has limited exposure in the caudal extension, especially the lower parts of the clivus.

- Before we go on, I would like to ask you, if you don't mind. It seems like almost the best indication to use retromastoid versus translab is really, is it coming through this neurosurgeon or is it coming through the ENT doctor? You know most, that's if the patient comes through the EMT doctor, through that referral, most patients undergo translab approach. But if it's a neurosurgeon who is in charge, most patients undergo retrosigmoid. Do you agree on that statement?

- I agree with the statement, but that doesn't apply to our practice here at the University of Wisconsin. A patient either comes to us or goes to ENT. We discuss all these patients. And I'll tell you the truth, after graduating from my fellowship and residency, I started enjoying the translabyrinthine approach more and more. Yes, I wasn't familiar when I was doing my residency, but as I scrubbed with these, in these cases with the ENT team, I'm becoming the main advocate of the translab. And although sometimes my EMT colleagues will say, hey, in this case, maybe retrosigmoid is better. If translab is better option in my mind, I will go for it. So-

- And what's the indication for the translab versus retrosigmoid, in your book?

- In my book, is the early identification of the facial nerve, and the better and positive identification of the internal acoustic canal during the very early phase of the surgery. And second main advantage in my mind is the patients wake up much better after the translab. They tolerate, doesn't matter the duration of anesthesia, they tolerate the translab better because you don't deal with the cerebellum. You don't deal with the intrinsic intradural structures that much. So and less headaches after the translab approach. These are the three main reasons I like translab.

- So what tumors go through to retrosigmoid for their resection? And what tumors go through translab, how do you do choose?

- Good hearing, serviceable hearing, doesn't matter the size. If patient agrees with the retrosigmoid and if hearing is important to that particular patient, we'll go with the retrosigmoid approach. Doesn't matter, I like translab approach, or I have preference, translab over the retrosigmoid. So level of hearing is a number one factor. But if there's level of hearing is not good, or level of hearing is right at the borderline and the tumor is four centimeter, we know that a four centimeter sized tumor, chance of preserving hearing is less than 10%. So then we discuss this with the patient and if the patient wants to give it a try, we'll try retrosig. If not, we'll do translabyrinthine approach.

- So in other words, every tumor where you want said hearing, you go retrosig.

- Correct.

- And any tumor that hearing's not important, you go translab.

- Exactly.

- Okay, fair enough, that's very reasonable. Go ahead and let us know about how you position and how you do this exciting operation, please.

- Great, we would like to do the translabyrinthine approach in spine position. If a patient's body habitus is okay, such as in this case illustrated here. If patient has a short neck, moderately big size, we can even put the shoulder rolls. But like this cases, this is a skinny patient, you don't need to do anything. Slightly turning 60 to 70 degree to the contralateral side and slight flection and making sure there's space between the chin and the sternum. That's the factors you need to pay attention during initial positioning. And as you know, in these cases, especially in the translab cases, you airplane the operating room table a lot, either way, right or left. And you need to make sure you have the safety straps around the patient. So you don't wanna have the unwanted surprises during the surgery. And we like to use the Mayfield head holder. Although some neurotologist may favor just horseshoe or gel donut in translabs. But this, I like Mayfield because it gives a steady position to the head. And you can use navigation in mapping the sinuses, I mean, in case you need it.

- After-

- Thank you.

- After the positioning, the next question is about the skin incision. That's also related to the patient's size and the patient anatomy. A small C-shaped postauricular incision, most of the time, is good enough to provide good mastoid exposure. And muscle dissection, we'd like to preserve the temporalis fascia and use it at the end of the closure. And then you reflect the paravertebral muscles in subcranial subpial layer. I'll briefly go over some surface bony anatomy, which is very important in translab as well as retrosigmoid approaches. This is after in the cadaver dissection, right-sided mastoid showing the superficial bony anatomy. We have a supramastoid crest. Supramastoid crest is a continuation of the superior temporal line. And there's a Spine of Henle here, which is located posterosuperior to the external meatus. And there's a supramastoid triangle, which is below the supramastoid crest, posterior to the Spine of Henle. For examples, this triangle will be the, is positioned superficial to the mastoid antrum. As you know, mastoid antrum is positioned superficial to the semicircular canals. So these are initial early landmarks in performing these approaches. We like to do wide mastoidectomy. Our neurotology colleagues call it saucerizing the bone. So you have to get enough light and the depth. So making the deep mastoidectomy defect, with kind of shallow defect. First thing you need to see the antrum of the mastoid, which is the coalescence of the superficial mastoid air cells. Then you skeletonize sigmoid sinus and transverse-sigmoid sinus junction. You need some kind of retrosigmoid to drill into, so you can retract the sigmoid sinus, especially there's not presigmoid exposure. That We have middle fossa plate. This is also important in performing the translabyrinthine approach that will give you the good access to the superior semicircular canal. You have superior petrosal sinus and jugular bulb inferiorly. Lateral. Inferior to the lateral superior semicircular canal, you'll notice the facial nerve. In this cadaver dissection, for demonstration purposes, we took the periosteum of the facial nerve. But in real life, we don't take the periosteum of the facial nerve. That will devascularize the facial nerve and may give unfavorable post-operative facial function. And there's a sinodural angle which is the dura between the superior petrosal sinus and the sigmoid sinus. In terms of the labyrinth, superior semicircular canal, will be facing the middle fossa dura. One good anatomical landmark of the superior semicircular canal, is the tiny artery, which is the subarcuate artery, that's a very good landmark to localize superior semicircular canal. And posterior semicircular canal will be facing the almost 90 degree to the posterior fossa presigmoid dura. Lateral semicircular canal is the first and early exposed semicircular canal. Before performing the labyrinthectomy, another structure we should be aware, but there is no importance the translabyrinthine approach is to endolymphatic sac. Endolymphatic sac faces the posterior semicircular canal in 90 degree angle. And is the communication between endolymphatic duct and the vestibule. We perform first a labyrinthectomy, removing the lateral and posterior semicircular canals. And then we move to the superior semicircular canal and drilled it completely. And at the final bony work, you have a so-called 270 degree exposure of the internal acoustic canal. This is very important when getting the anterior aspect of the acoustic neuromas. Some drawings, again, adopted and modified from the Jackler and Brackmann "Neurotology" book. Opening the dura, it depends on the surgeons experience, but you, as you know, we cannot repair the dura, presigmoid dura, after we open and work on that several hours. So nowadays I don't even open in any shape. I just remove part of it and leave and other parts right in front of the sigmoid sinus to preserve the cerebellum. We'll go to now, this is again, another cadaveric dissection translabyrinthine approach. Once you open the dura, you see the intradural structures, seventh and eighth nerve complex, and the vasculature. Inferiorly you will see the posterior inferior cerebellar artery and its branches. And you will see the anterior cerebellar artery looping between seven and eight. At the depth after your exposure, You will see the basilar artery and the sixth nerve. And this is a gain for demonstration purposes. A much wider exposure than the normal translab we will do. You'll see third and the fourth cranial nerves. And I will, another patient we just recently did a translab. Initial exposure by my ENT colleague. Internal acoustic canal. Vertical crest. Early facial nerve. And the labyrinthine segment is gonna be somewhere here. We know that labyrinthine nerve is more susceptible at the labyrinthine segment. And rolling the tumor, early identification of the tumor. This is not very big tumor. Then going back to the presigmoid cerebellar dura, opening dura All aspects of the canal. So this 270 degree drilling helps you to get this part of the dura, inferior of the internal acoustic canal dura and superior. That devascularizes the tumor early. See all the blood supply to the tumor will be coming from this dura than from the brainstem. You create a plane, you preserve that plane. No we are coming to brainstem. Since this is not a very big tumor, it's approximately two centimeter, there is that plane, two layers of the arachnoid is nicely preserved. So one arachnoid is on the tumor side, another arachnoid is on the brain side. Here we go, early identification of the facial nerve is very robust, nice nerve. But question is, is it gonna be the same way at the porus? So sometimes you get wrong and you get very optimistic. Oh nice nerve, it's gonna be nice dissection, but at the porus, nerve may be splayed and make the dissection more difficult. Debulking and moving around. See the technique you said, spreading. And in this one, by just peeling, it works, because there's a nice plane and the tumor is not that big. You are not fighting with the tumor.

- So I see that you grabbed the arachnoid and push it on the brainstem.

- I wish all neuromas-

- I like this side cutting.

- Is two centimeter or smaller, but it's not, unfortunately. And then, here are the lower cranial nerves. So as you see, it's a dynamic surgery. You keep moving from the lower to the upper part of the dissection, or medial to lateral part of the dissection. I saw the facial nerve. No I am gonna amputate the eighth nerve. This is eighth nerve, and there's a loop of AICA right in front of it being eight and seventh. This is a very good anatomical localizer. I emphasize this all my teachings here. See the ninth, and this is eighth nerve is unprotected at the brainstem entry. And we just got the glimpse of the facial nerve. Now back to the canal, again. Over and over again, same principles, going back and forth. Other side of the internal acoustic canal dura and rolling the tumor. Facial nerve. And the facial nerve at the porus and cisternal segment. And there's a nice anatomy here. We are seeing the nervus intermedius just here. See, it's going along with the facial nerve. Here is the facial. Here is the nervus intermedius. And the main AICA.

- This is a really nice example of how to dissect a nerve, Mustafa. A really nice video, demonstrates the technique.

- And sometimes it's massaging motions. Very small, shrink repetitive motions just create a plane. See here is becoming stuck. Now I go back to the other side. I'm moving back and forth. From canal to the porus, from brainstem to the porus and meeting at one point.

- Let's go to the last part of this video.

- Nerve again, AICA branch. See the nerve, nerve here, here, porus here.

- That's the more stuck part at the porus right there, isn't it?

- Correct, right here. But I learned taking my time. Anytime you rush, especially at this stage of the surgery which is the last piece of the resection and also when the surgeon and everybody is the most tired, you have to take time.

- I agree. Yeah, the most critical part occurs when you're the most tired and everybody wants to leave.

- Correct.

- And that's when you need to slow down and have the most focus and concentration.

- And with your dissection plane, there's a nice arachnoid either side of facial nerve. So you shouldn't be right at the nerve with your sharp dissection. You should give a couple of millimeters of distance when you make the cuts. That's what I was doing. See this nice, nice plane here. That's an arachnoid, that's not there nerve. And see here, I'm going to cut that arachnoid and that's right now, I'm winning.

- Yeah, you have to really hug the tumor and leave the arachnoid on the nerve, just like you're doing right now. And the suction is at a very low level, almost none.

- Suction is, I'm adjusting with my thumb. The tumor is gone, nerve was nicely stimulating, I did 0.05 milliampere. And we packed the inner ear with the muscle. You're gonna lay the fascia, pack the fat crest. And patient woke up with a grade two facial width, ten days ago.

- Very, very nice technique, Mustafa. Very meticulous technique. Something that is truly the foundation of microsurgery and what makes it quite effective. So you put the fat in and then put the fascia over it. Am I correct?

- First fascia laying over the mastoid segment of the facial nerve and then packing the fat.

- Okay, very nice result.

- And the post-op. Now we have a case example. This is a 60 year old male presented with hearing loss, dizziness and walking difficulty. And we'll go to the video demonstrating this translabyrinthine approach. This is again, same as shown in the pictures, making sure patient is positioned safe. In translabyrinthine approach, it's crucial to obtain abdominal fat graft at the early phase of the surgery. And then we start, after the elevating the skin flap, we start with the saucerizing the bone edges, and the mastoidectomy. You see the superficial mastoid air cells. And we like to use start with the large burrs, like five or six cutting burrs. As you progress deeper and come to the sigmoid sinus, we go to the diamond burrs, like four or five millimeter diamond burrs Middle fossa dura is exposed and the bone plate over the middle fossa removed. Now we are going to do a labyrinthine bone. And labyrinthine bone is very dense, much, much more dense than the other parts of the mastoid. And the final exposure showing the vertical crest or so-called Bill's bar and the complete exposure 270 degree exposure of the internal acoustic canal. Now we are opening the dura of the internal acoustic canal and identifying the superior vestibular nerve. In this particular case, that's the nerve of the origin, tumor originated. And then extending the dural opening in the presigmoid region. And identifying the tumor and establishing the early part of the tumor. And then you start debulking before we continue with the further dissection. As you see here, at the posterior superior aspect, and this is a cystic tumor. Cyst wall was dissected. And we performed suction pressure dissection identified all aspects of the tumor. And then internal debulking. Here we identified the eight nerve complex, which is being sacrificed since patient has no serviceable hearing. This is the tricky part. Sacrificing may sound easy, but there's a nice loop of the anterior inferior cerebellar artery right there. And I've seen cases that that was injured during the sacrifice of the eight nerve. Then we continue dissecting and identifying the seventh cranial nerve, which anatomically we know, is gonna be anterior to the ventral to the eighth nerve entry zone. Dissection continues on between suction pressure dissection, internal debulking and identifying the facial nerve in the canal, as well as in the cisternal segment. Here is the facial nerve. I'm using the facial nerve stimulator. In every case, we use the facial nerve simulator. These dissect, also you can use as a dissecting tool, you can constantly stimulate and dissect, but we don't prefer constant stimulation at the higher levels. That can tire the nerve as well. Cystic wall of the tumor has been sharply excised. And now this is again, cystic wall and the facial nerve is right here. And as you know, Aaron, these cystic tumors are very, very stuck to the nervous, arterial or brain structures. And it was the case in this tumor too. So after identifying everything, last piece of the cyst wall excised and brain stem is seen. And nerve was nicely stimulating at the lowest milliampere, which is the most important predictor of to post-operative facial function. Then we divided abdominal fat graft into multiple pieces. And we filled, packed the mastoidectomy defect. And the patient has early postoperative period, grade three facial weakness. And in two months, it returned to the normal grade one function. One important thing is, as seen here, this fat graft, it looks really large. And it's sometimes my residents tease with me say, oh, you removed the tumor, replaced the tumor with the fat graft, but this gets contracted. And it's very, very crucial to pack enough fat, not loosely, tightly. Of course you don't wanna compress the facial nerve. And this patient had the post-operative MRI shows the gross total resection, and he did very well.

- I have a question for you here, Mustafa, before you go to the next case. You obviously do facial EMG, that standard of care. Do you monitor anything else doing acoustic neuroma surgery?

- If it is moderate to large size tumors less than three centimeters, I don't monitor anything else. But if it's a very large sized tumors and there's a significant brainstem compression, and if I predict that I'll be doing more dissection on the brain stem, then I will monitor motor evoked potentials and the somatosensory evoked potentials. And during preservation cases, of course, brainstem auditory evoked potentials and the cochlear nerve monitoring.

- And how about, do you, when you say motor evoked potential, that's gonna really cause a lot of motion during surgery. So you have them sort of run potentials frequently. Obviously don't do any microsurgery during that time and just let them run it every 10 to 20 minutes. Is that right?

- I would like to do in the early phase of the brainstem dissection, every 30 minutes. And if I get in the critical points, every 10, 15 minutes. But they let me know before they run the motor evoked potential. Because as you just mentioned, it cause a lot of artifact and movement in the operating room table.

- This is a good time to ask you. When you have a big tumor and it's really attached to the nerve, do you leave a piece and do radiosurgery if it grows? Or do you routinely try to do gross total resection of the tumor?

- Yes, I will try to do gross total resection, but not at all costs. If patient is young and I still have a good stimulation, I will resect that piece. If I am losing the stimulation from the lowest to, for example, 0.05 to it became like 0.2 stimulation, then I will leave that piece. That's a good indicator I am causing neuropraxia of the nerve at that level. If patient is old, then definitely, I will leave the small piece and observe it afterwards.

- Please go ahead.

- This is another example of the translab just to demonstrate size is really not important in choosing these approaches. Quite large base ovoid type of tumors with a lot of brainstem compression in a relatively young patient. And this is very important indication for translabyrinthine too. Dizziness, especially intractable incapacitating dizziness, is a good indication for surgery. It's also a good indication using the translab because you are basically doing vestibular neurectomy with the translab. And this case, another important point in these large tumors, presence of vasogenic edema. In this case, there is no vasogenic edema. I know that I'm not gonna be spending a lot of time dissecting the tumor off the brainstem. If there's a vasogenic edema, it's very likely there are large peeled veins, tumor draining veins part of the time. And I have to be very careful. And that's a good indication I will point to my residents before surgery, whether or not surgery is gonna be longer or more difficult. In this case, we chose the translabyrinthine approach. Patient we achieved the gross total resection, fat graft, and the patient has a grade two facial weakness in the early post-operative period. And in three months, improved to the normal face from grade two. As you see, even in three months, fat graft got contracted. So, and in one year this will be much smaller. It's very important to pack enough fat to avoid cerebrospinal fluid leak in translabyrinthine approach. Another example of the 60 year old patient with the hearing loss and walking difficulty. He underwent a subtotal resection via retrosigmoid craniotomy at outside facility. And then for unknown reasons, right after the subtotal resection, patient also received CyberKnife stereotactic radiation. And in spite of those, tumor continues to grow and came to our attention. And we recommended the translabyrinthine approach. Again, showing the first part of the surgery, performing the mastoidectomy. Please remember that this is previously operated and the radiated tumor. So in these cases, my experience tells me tumor is gonna be very fibrotic, dense and there will be a lot of scars, subarachnoid, arachnoid scars. So in my mind, this is gonna be long surgery and I prepare myself and my team accordingly. Again, middle fossa plate his removed after thinning the bone. And sigmoid sinus is exposed. we are going to the presigmoid. And we'll be drilling the same circular canals. As you see here, one of them is open and is very dense bone. It's embryologically different origin of bone. So it's easily identifiable, but with experience, you know, still, you need experience to identify it. At early stage, you won't be. And then after drilling the semicircular canals and the labyrinth, we are exposing the internal acoustic canal here. Right, and the go with the smaller drills, as we progress in the drilling process. Coarse diamond to fine diamond, depending on your experience and the need. And we start seeing the dura of the internal acoustic canal right here. And facial nerve with its periosteum just here. And the sigmoid sinus, my neurotology colleague is retracting with the suction aspirator. And so-called 270 degree exposure of the internal acoustic canal. And we just got the glimpse of the incus here, and we need to make sure we pack that region with the muscle after the surgery very well. Now we are opening the dura of the internal acoustic canal. First, you see the nerve of the origin which is the superior vestibular nerve. And superior vestibular nerve will be amputated and rolled from lateral to the medial side and vertical crest or Bill's bar. And then we continue with the opening the internal acoustic canal dura towards the presigmoid dura. Here, you don't see many very dense adhesions, but as we progress more intradurally, you'll see scar from the previous surgery, which will make this surgery and the dissection quite difficult. We are extending the opening of the internal acoustic canal dura. This is a presigmoid dura. You'll see there's a dense scar here from the first surgery and we see the sigmoid sinus. One important thing, we need to keep sigmoid sinus moist. And we need to make sure our assistant is not sleeping during this dissection, but constantly irrigating the sigmoid sinus. Now we'll start seeing the adhesions from the first surgery. There is not clear plane. And I got some arachnoid I opened and I'll spread CSF to relax the cerebellum. Part of the residual or recurrent tumor right here. I'm trying to find a plane and identify the lower aspect of the tumor. Jugular bulb is here, jugular foramen is gonna be somewhere here. We can go to the next video. Again, this is the other dissection. Here, there's significant arachnoiditis from the first surgery. I'm having hard time to identify clear plane. Sharp or blunt dissection, or spreading actions of the bipolar forceps, I use all of them. I don't have any dogma in my dissection. I'll use only sharp dissection or blunt or both, whichever one necessary. And as I said before, using facial nerve stimulator as dissector is very helpful too. It has very sharp edges, and you can use this dissector. And you can get the little bit from the facial nerve, which might be warning sign for you to realize you're close to the facial nerve. Here I'm getting to the plane That is a previous arachnoid scar. Now I'm going with sharp dissection, cutting that thickened arachnoid. And I'm trying to find the seventh facial nerve entry zone. We didn't have a good detailed operative note from the previous surgery, but is very likely they may have sacrificed eighth nerve, its entry zone during the first surgery. So I'm not positive about the eighth nerve, but I need to first find something that will lead me to the facial nerve. Upper aspect of the tumor. Usually trigeminal nerve is in this location and is significantly compressed. See the arachnoid, upper part of the brain.

- I really like what-

- And dissecting.

- I really like what you're doing. If there's ever a question, just try along the brainstem. That's the best way to protect the facial nerve.

- Correct.

- And the other thing is that when it's so much scar, usually the facial nerve position is very unusual. So you have to be very, very careful. It will be on very unexpected locations in redo operations. Go ahead please.

- Correct. As you know, in normal, fresh surgeries, facial nerve position is when you expose, you don't know. But for the larger series, most common location of the facial nerve will be anterior position and or second column will be anterior superior, anterior inferior, or superior posterior. Very, very, very rarely you can have posterior loop position facial nerve or completely encased facial nerve. If you have a complete encased facial nerve, first thing you should suspect is this might be a facial nerve schwannoma, not the vestibular schwannoma. And same with the lower cranial nerve schwannomas. In my life, I encountered two cases of the lower cranial nerve schwannoma. And patient had hearing loss, dizziness, but no lower cranial nerve deficits. And by looking at the MRI and that MRI appearance, you wouldn't be able to say this is a lower cranial nerve schwannoma. But on exposure, very nice plane between facial nerve and the tumor in the canal or in the brainstem and eighth nerve too and you cannot see the lower cranial nerves, you should realize this might be a lower cranial nerve schwannoma, not the vestibular schwannoma. So you should be ready for the surprises and like any surgery in acoustic neuro surgery as well. Now I went back to the canal and I'm dissecting the tumor. Applying slight traction with my suction. And then doing the sharp dissection with my micro scissors. This is the facial nerve in the canal. See, it's gonna be very, very splayed at the porus level, which is the most difficult part of the dissection in these large tumors. I identified the facial nerve. Now I realize I need to debulk a little more. And the Cavitron ultrasonic aspirator is a good tool to perform this debulking. But I don't like using very high power and high suction, especially the suction power is very important. You can easily suction the tumor and the tumor will apply traction to the nerve. And you may lose the function of the nerve or your stimulation. Piece by piece, taking time, being patient is key in the acoustic neuroma surgery. Again, Cavitron ultrasonic aspirator not very high power and not in the high suction power. After initial dissection, I start mobilizing the tumor more and more. And with central debulking and dissection. Brainstem, just again, came to the view. And I use a suction I can adjust with my thumb and I learned this technique from my dear mentor, Dr. Jacques Morcos. And it becomes a subconscious move in your dissection. You constantly change your suction with the thumb and even you suction the facial nerve, but you're not really applying the suction. And that, your suction left-hand or right-hand, is your not only suction tool, you're retracting the structures, also, you are dissecting with it. Like right now, I am kinda, just gently using my suction to push the structure or pull the structure to dissect. And protecting your plane with the non-sticky Telfa patties. So here is the difficult part, it's very stuck. Dissect, debulk, dissect, debulk. It's the same principles we do in many tumor oncologic surgeries. Again, I went back to the canal again. I'm changing back and forth, canal, brainstem. And 'cause you need to gain space. If you work from one angle, you will be very limited with your dissection plane. So you need to dissect and debulk same time. Cavitron ultrasonic aspirator again. It's fibrotic tumor, it's radiated before, surgery before and it's giving me really hard time.

- Where's the facial nerve here, Mustafa, can you orient us?

- We haven't seen the facial nerve at the brain stem entry site. Now we are coming there. Facial nerve is gonna be somewhere here. That's the problem, after even resecting this much, I wasn't able to see the facial nerve here. That's why I'm going back and forth between the canal and the brainstem. Get the sense of where the facial nerve is really positioned at the porus or in the cisternal segment. This is the canal again, performing the sharp dissection. Now I'm coming to the brainstem entry zone of the facial nerve here, Aaron. As you see, arachnoid adhesions here. Problem with the spine positions, different from the sitting position, the CSF and the blood accumulates. But you know, this is the payback between your relationship with the anesthesiologist. If I say, I wanna do a sitting position, they can sleep almost a month before the surgery. So again. This is, see the brainstem. All adhering to the brainstem. So instead of peeling in this, I'm doing the sharp dissection and going to do my sharp facial nerve stimulator.

- Now, I sometimes grab the arachnoid and sort of pull it off the tumor and leave it on the brainstem. That really works well as well, especially for tumors that are a virgin. Go ahead.

- Correct. See, I think we are coming to the, now I am right here, I realized I am winning the game, I'm moving faster. And tumor is completely peeled. Facial nerve is barely visible here at the brainstem. And it's nicely stimulating. This patient woke up with the grade three, progressed to the grade five. But function returned to the grade one in one year. So only good predictor at the end of the resection will be the nicely stimulating nerve at the lowest milliampere. Post-op MRI showing the gross total resection. Another tumor, 58 year old male presented with a large, large tumor. Here, you see the vasogenic edema. This is different from the other large tumors I just showed you. This will make your dissection plane very difficult. But we were able to do a gross total resection again. You'll see the almost same amount, maybe more vasogenic edema. And in these cases, if there's a pre-operative hydrocephaly, I usually put ventriculostomy in large tumors larger than the four centimeter with significant brainstem compression and edema. This patient had a good grade three function after surgery and grade one function at one year. Another one, like I just was mentioning with hydrocephaly pre-operatively. This patient came to our attention rather in an urgent situation. So he was seeking medical attention at many centers back out forth. Gama Knife subtotal resection, and suddenly he became lethargic and he developed hoarse voice. As you see there's an optic hydrocephaly here. So we put ventriculostomy, stabilized him and took him to the translabyrinthine resection next day. Again, after completing the translabyrinthine approach. Presigmoid dura, facial nerve. Early decompression of the debulking of the tumor, because in spite of all these maneuvers, I had hard time to see the cerebellum. Large cyst, I wanna move on and decompress this part early, so I can finish the surgery, the more difficult parts in reasonable time. So solid parts of the tumor, debulking.

- Yeah, the ultrasonic aspirator is absolutely life saving in these procedures. It's just no way around it because it's so gentle in removing the tumor.

- And the brainstem again. Here, preserving the brainstorm with the patties and dissecting and debulking. You won't be able to see facial nerve at the brainstem early in these cases. You have to remove at least 60% of the tumor before you start seeing any nervous structures at the brainstem. Sharp dissection. And these tiny brainstem perforators can be very, very adherent to the tumor capsule. You should spend time to preserve these. No, at all costs, they should be preserved. Not even thinking little bit bipolar coagulation to stop bleeding. If you have bleeding from these perforators, just put gelfoam or surgery salve and slight compression and try to stop the bleeding while preserving them. Now again, after debulking enough, I went to the canal side and I'm getting the tumor, rolling the tumor from canal to the lateral to the medial direction. Usually there are these large veins, if they're just some veins stuck to the capsule, leave them alone, but like in this case. But there are some large veins draining the tumor. Those can be very, very problematic during the surgery. Just if you have any bleeding again, just packing, not even trying to coagulate to stop the bleeding. Again, canal side. And as we know, vascularity of the tumor comes from either brainstem anterior inferior cerebellar artery branches, or the dura of the internal acoustic canal. So early identification of these can be very helpful in dissecting and removing these tumors. Cutting the blood supply will always help. And some of these tumors are exceedingly vascular. Again, another tiny brainstem vessel. I am peeling it from the tumor. And this is the fascia we obtained during the initial exposure, temporalis fascia. You just lay over the part of the mastoid segment of the nerve. and the inner ear should be packed with the muscle. And then we place the fat. This is the post-operative MRI, again, big fat. This patient required ventriculoperitoneal shunt placement. He had to persistent ventriculomegaly. And when we removed the ventriculostomy, he developed severe spinal fluid leak and post op MRI one year, he's doing very well with normal facial function. Another cystic tumor similar to the previous one. And same approach, translabyrinthine gross total resection grade three facial weakness early. At one year, improves to the grade one because it was stimulating nicely at the brainstem. And this is the patient, young patient, very heavyset underwent retrosigmoid craniotomy at outside institution for resection of this tumor. And due to the extensive cerebellar swelling, they abort the surgery and they transferred to our service. We placed to ventriculostomy and we performed the translabyrinthine approach and achieved gross total resection. He did very well with normal patient function. This is a 55 year old male who underwent the retrosigmoid craniotomy in Europe with subtotal resection. We don't have the pre-operative imaging, but this is the post-operative image. It's very good resurrection. I mean, there's no question. They left something in the canal and a little bit tumor in the porus level and then they radiated this spot in 2009. In 2011, tumor becomes this big and he is even more dizzy. We did the translab approach and achieved the gross total resection in this case too. Again, these are all difficult cases. Previously radiated and operated cases, translab approach works very well in these cases. And patient had no hearing, even before his first surgery in Europe. Identifying the tumor early, patties on the sigmoid sinus here and the presigmoid dura. So this presigmoid dura is kind of nice barrier between you and the cerebellum. You don't deal with the cerebellum at all. As you see, I'm not retracting anything. Dura is the best retractor for the brain. Aspirating the CSF. Going slow at the beginning. Identify the structures.

- And here, you can't overemphasize. Yeah, you can't overemphasize the issue of debulking in these tumors, where you in terms of mobilizing the tumor. And people just don't pay enough attention to that, I think.

- One the important thing, before you do any kind of debulking and intracapsular dissection or a resection, you should map to facial nerve first at the high amplitude stimulation to avoid to have facial nerve injury in case of very, very unusual course of the facial nerve. Especially as you mentioned in the previously operated cases, because you don't know where the facial nerve is going to be. It can be very much, very likely it can be clamped with the arachnoiditis and it can be between the tumor too. Now, I'm in the canal. I'm using this nice ENT tool, flat knife. Just peeling the tumor from the facial nerve. There's some dural scar here. I'm gonna cut that then remove. How often do you use the translabyrinthine approach, Aaron?

- I don't use it often. And I think you are, I completely agree with you, we should use it more often because patients do recover faster. I use retromastoid because often, the tumors I do are larger than three and a half centimeter or four. And we do radiosurgery a lot for the smaller tumors. And so when they're that large, I just have been more trained to use the translab, sorry, the retrosigmoid approach. And it's just more my familiarity with the tumor. And when they're that large, I don't feel obligated I should remove all the tumor. I actually leave a small piece of the tumor on the nerve and in the IAC and just do radiosurgery if the tumor grows. And because of that strategy, I have used mostly the retrosigmoid approach. Let's go to the next stage of this video. Thank you. You can see how the debulking is so important here, Mustafa, to just get this capsule, the tumor out of your way. And the moment you debulk this, you can roll this capsule. And that's absolutely key in acoustic neuroma surgery. The more you debulk the faster, the more efficient and the safer the surgery goes. The problem often is that these can bleed a lot. And the more you debulk, the more bleeding you have, then the plane gets obscured, but you cannot lose the, or sorta disregard the respect for debulking of these tumors early on to make their resection much more efficient.

- Correct. So now I came to the brainstem and you see the significant arachnoiditis, arachnoid adhesions from the first surgery as all the structures are clamped. But I am using my suction to hold and apply slight traction on the brainstem side, stretching the arachnoid, then doing the sharp dissection. So I can roll the tumor from medial to the lateral side. And established enough dissection, it's becoming more obscured. Then you go back to the debulking. So as you said, debulking is very important step of the resection of these tumors too. And then this is again, tougher part of the tumor, where they probably coagulated the internal acoustic canal dura.

- I assume you were looking for the facial nerve here.

- Correct, correct. And then you see the veins here, superior petrosal vein complex, As you know, these are multiple veins, so we should preserve them. I'm looking for the facial nerve without any early luck, but we'll get it eventually.

- Here it is, isn't it?

- This is in the canal, yes. It's stimulating nicely. It seems like in the canal, there's a nicer plane, so I can roll the tumor from lateral to the medial side. And then we are coming to the porous level nerves here. Since this part is on touch before, it's much easier. That's the eighth nerve. I just pull it and amputate it. And for some reason, I like this curve scissors, they are, I hold them away from the structures. And removing again, piece of it and then debulking further.

- I think when you expose it through the IAC, it gives you which direction is it going. Is it going superiorly? Is it going in thoroughly? Is it going anteriorly? And it gives you a lot of confidence in terms of how to dissect the brainstem part of the tumor pole.

- Correct. That's the main advantage, one of the main advantages of the translab approach. Early and very positive identification of the nerves in the canal and at the porus level. And that will lead you to where a nerve might be in the brainstem side

- I agree.

- So getting the early identification.

- I agree.

- So this is the facial nerve at the brainstem.

- So you're essentially peeking underneath and seeing the nerve without rolling the tumor. You don't wanna roll it sort of up side down or something in that direction. You wanna always do it medial to lateral, as you just said.

- Correct. And then I think we did the gross total resection. If we can go back to.

- And this is the last step of that operation, Mustafa.

- And again, there are veins here. And the small tiny perforator branches of the AICA. Rolling the tumor slowly, away from the brainstem and the brainstem entry zone of the facial nerve. Sharp dissection.

- I think trying to grab those arachnoids with a very fine forceps, Mustafa, and just peeling them toward the brainstem is sometimes very effective and-

- Correct.

- Sorta it requires less work, the micro scissors always seem to require more work to dissect using them. And so, I have found that really helpful of using those fine, very fine forceps and just tearing those arachnoid membranes toward the brainstem. You can see the nerve is very adherent here, isn't it?

- Correct, our nerve is here. And these are different angled sharp flat dissectors. I'm trying to create a plane between nerve and the tumor. But I'm taking my time. And now I'm using arachnoid knife. If you cannot achieve nice dissection with one instrument, in my mind, you should switch to do another instrument or another maneuver. So now I'm using the diamond knife, diamond arachnoid knife. And now the facial nerve is right here. Entry zone, the cisternal segment and it will be porus somewhere here, see, and gentle traction.

- You know this when, Mustafa, I would consider leaving a small piece of tumor, when it's that adherent.

- Correct.

- I know-

- So what I, what I do, I poll the stimulation. Continue to stimulate, I'm okay and he'll be okay. And this patient already had radiation and surgery. So he doesn't have, I don't think he will have a good third chance. So this is the part again, the entire nerve, part of the tumor.

- Yeah, the forceps would work really well here. You grab those arachnoids and just leave it on the nerve.

- Correct, but you don't, it's very small area and the blood and the CSF-

- I agree.

- Obscuring your view. So you won't be able to. So now, I am able doing the spreading motions. And I'm holding my breath.

- It's very adherent there.

- Yeah, but we got it. And unfortunately, for some reason, we don't show the surgery. But it's gross total resection, as you see. It's nice, he woke up with the grade three. And progressed to the grade five in two weeks. And returned with the grade one in two months. And he's been tumor free, I think it's two, three years now. Another cystic tumor. I just wanna mention the importance of this, again, vasogenic edema here and the large. And this patient had biopsy, cyst aspiration, stereotactic radiation gamma knife, and VP shunt placement, and is wheelchair bound for six months and was sent to hospice in 2014 in the United States, with the benign brain tumor. So he was wheelchair bound. He was severely ataxic. So we took him to do surgery. And for sake of time, maybe we should skip, or should we continue with the video?

- We can just look at the selected portion of this video. Here we go. So we can skip the opening, if that's okay with you. Here it is, I think.

- Yeah, retrosigmoid craniotomy. And see, I'm trying to find the, again, some structure I can identify. And I'm using sharp dissection. Lower cranial nerves finally, I see here. I use the scissors, this kind of sickle shaped scissor. I called it samurai scissor. It's very, very helpful, very ergonomic. And see the lower cranial nerves. And this patient had lower cranial nerve deficits too. He had a pack placement. Six months, couldn't get up, he couldn't eat. Those veins I was mentioning, large tumor veins, they are red, they're like AVM veins, draining veins, they drain. And look at the amount of scar here. You should not just biopsy and cyst aspiration. If you wanna do good resection, you should perform a subtotal resection, then radiation and shunt. But just cyst aspiration biopsy creates scar and it doesn't help the patient. And radiating this six, seven centimeter cystic tumor is not good treatment. And patient had the retrosigmoid craniotomy before. Now I found the tumor. And this patient had the grade three facial weakness before surgery. So he lost almost all of his cranial nerve functions other than the one, two and three. So at the end, we perform the gross total resection. Nerve was stimulating at the 0.2 milliampere. I wasn't expecting that nerve to be simulated at the lowest amplitudes, but it was at least stimulating. And he woke up the grade five facial weakness. So he was grade three before, but now in two months, his facial function is improving and he's walking and he's eating. I mean, it's so. In this patient, facial nerve function is not important. It's important is the making him more functional, getting him up from the bed. And he can walk, he can eat and he can't return, he can go back and forth. So this is all seven. This is all seven. Large vein. Nerve is stimulating still, high, but it's still good stimulation. It's anything above 0.2, I wouldn't have a good faith on that outcome of the patient. Gross total resection. And what I showed you, good gross total resection. I think this concludes to our first section. The main conclusion I will draw for trainees and other neurosurgeons, as a neurosurgeon, doesn't matter acoustic neuroma surgery or any kind of surgery, you have to be versatile. And you need to be aware of your options. So translabyrinthine approach provides a nice exposure and I think it's very crucial to acoustic neuroma surgery. Thank you.

- Really great job Mustafa, as expected. And I really enjoyed watching the great technique, no doubt about it. So here is the, as you said, last part, I'll say the last portion of the first part. And we invite our viewers to also watch section two, which will demonstrate similar techniques for retromastoid and middle fossa approaches. Again, thanks again, Mustafa.

- Thank you, Aaron.

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