Transcript

- Good morning and welcome to the Neurosurgical Focus Podcast for the September, 2012 Issue on Acoustic Neuroma. I am James Liu from the Neurological Institute of New Jersey at the New Jersey Medical School. And we are delighted to have professor William Couldwell from the University of Utah to discuss his paper on Surgical Approaches for Resection of Vestibular Schwannomas Translabyrinthine, Retrosigmoid, and Middle Fossa approaches. Dr. Caldwell.

- Welcome James. It's an honor to be here.

- We wanted to discuss your paper on the various approaches to Vestibular Schwannomas, and would like to go through a series of cases and see how you determine what type of approach to choose based on the pathology and the age and presentation and so forth. So without further ado, let's, go on to the first case here. This is a 62 year old female who presented with right-sided hearing loss, which was determined as non serviceable based on the audiogram. She also has severe gait ataxia. And on the scan that you see to the right, she has a right CP angle mass that extends into the internal auditory canal. There's some degree of compression here, and there's also some enlarged ventricles.

- So this is an interesting case. She's got this sort of medium-size acoustic tumor with some brainstem compression, but there does not look like there's enough volume here to cause fourth ventricular upload structions So the question that I have is whether the hydrocephalus maybe related to the tumor and another mechanism, and there is some literature that has demonstrated that there's a higher protein concentration in the CSF in patients with Vestibular Schwannomas. And this may be contributing to her hydrocephalus, which may be communicating in this case. So the management then decision is, do you manage the hydrocephalus separately or do you go after the acoustic tumor? First probably what I would do in this case is remove the acoustic and see what happens. Although I certainly wouldn't have any problems if people wanted to address the hydrocephalus separation.

- Let me just show you a few more images here, a coronal and then a T2 axial.

- Yes, I think this sort of verifies what my suspicion was on the first images that there is a medium to a larger acoustic tumor, but it does not appear to be causing fourth ventricular obstruction. So in this case, I would probably choose to remove the acoustic tumor first see what happens--

- This was an interesting approach and strategy for us. And I'm just gonna show you one more film, which sort of tipped us to do the strategy that we ended up choosing. You could see this as a very well aerated mastoid and our approach for this type of tumor that extends all the way out to the fundus with non-service for hearing our preference would be to do a translabyrinthine approach in the mastoid and temporal bone. But as you can see here with such a well aerated mastoid, this certainly increases her risk of a postoperative CSF fistula. So what we decided to do was we did it in a staged fashion where we put in a ventricular peritoneal shunt first, and two days later, we then took her back for a translabrynthine approach. And we were able to achieve a gross total resection. And fortunately she did not have a CSF leak and she had good normal facial function afterwards. And so the reason behind that was we felt that if we did the translabrynthine, certainly she would have a high risk of CSF leak probably from underlying pressure, in addition to the aerated mastoid air cells and having a shunt in place would help decrease the pressure upfront and then would help with the closure at the same time after her acoustic operation.

- So I think that that's a reasonable strategy, Jim, I too would choose a translabyrinthine approach on this case for all the reasons that you mentioned. There's a lot of tumor in the canal. It offers you perfect visualization of the facial nerve at the canal and it's certainly of a size that you could easily remove through a translabyrinthine approach. The nice thing about a translab approach in this case as well is that the eustachian tube is packed off at the time of surgery. And despite the aeration of the mastoid that usually controls the CSF leak--

- So we have here some inter-operative pictures. If you could just comment on how you would take us through your approach and positioning briefly.

- Sure, so this is a classic approach that's used by the otologist where the patient is usually left supine with the shoulder bump, and then the head is turned and then this retro mastoid incision is used, and this can be used. This is a superb incision actually the ontologists use this curved incision and I like to use it because it gives us perfect access to round the area of the external auditory canal. The one caveat that I have with this approach is that they tend to turn the head quite significantly. And if you have a situation where you have a small sinus and jagular vein on the contralateral side, and then they put at risk the ipsilateral sigmoid sinus with their drilling, then it can cause some problems with venous outflow and we've had problems with intra-operative venous bleeding.

- And so here are some inter-operative photos here you could see in the upper left, the mastoid has been drilled out. And just to orient this as the middle class of dura, here's the sigmoid sinus jugular bulb and a pre-sigmoid dura. And here's the fallopian canal where the facial nerve is and here's the entrance to the middle ear, which has to be sealed off at the time of closure to prevent a CSF leak. And once the dura is open, you could see the tumor is located here. And just as you said, one of the great advantages of this approach is you can come pre sigmoid and virtually there is no brain retraction so we're able to do this without any fixed metal retraction and we're able to take out this tumor readily.

- Yeah in fact, when we do a translabyrinthine approach, we don't even put the patient in pins. We just roll the head over. And because you don't need a retractor, the approach is putting right into the tumor. And so the strategy is to core the tumor and to dissect around the circumference of the capsule without retraction. It's a superb approach--

- Could you please comment in terms of your own surgical pearls and nuances as to when you're dissecting the tumor off of the facial nerve, whether you're going medial to lateral lateral to medial or both depending on the situation.

- Sure. So in general, we'd like to do a lateral or a medial to lateral dissection of the tumor off the nerve, but in a translabyrinthine approach, that's less relevant because what you're worried about doing when you're using a retro sigmoid approach and you wanna go from medial to lateral, is you wanna avoid putting traction on the eighth nerve and the filaments of the eighth nerve as it perforates the end of the fallopian, or at the end of the internal auditory canal. That's obviously less of an issue here, you're sacrificing hearing upfront. And so we'll dissect the tumor in both directions in a translabyrinthine approach. And I like to use the otology instruments, the hooks, the very fine hooks and use them to find the interface between the tumor and the nerve. The other thing that I like to do is I like to hook up automatic irrigation, and this is a drip system that I use. I've used it for years and it continuously irrigates and keeps the nerve wet during the dissection. And it helps you identify arachnoid Plains easier. And so a very good tool that avoids some of the heat and desiccation that we see with the modern day microscopes--

- I think that last point is a very good point the heat generated from these microscopes very quickly desiccates some of these nerves and cause irritation. And so I liked your idea of the one trick that I've learned from my otology colleagues is using the double barrel suction irrigator and leaving it on that continuous irrigation to achieve that similar effect that you mentioned.

- So here here's the post-operative pills and she had a nice result and let's move on to the next case. This is a 41 year old female. She had a large acoustic neuroma and she had a prior retro sigmoid surgery by another surgeon at another institution and it was followed by radiosurgery about six weeks prior to her presentation. And she presented to us with decreased mental status, decreased speech and spastic quadriparesis. And here is the film that you see here.

- Yes so a large tumor that was approached a retro sig, and you can see the opening made here. And the majority of the mass I presume is still remaining. So the question is what to do this point, we've had similar cases and I published cases whereby on these larger ones that undergo radiation therapy, and whether you call it radiosurgery or stage radiosurgery, 'cause they often do that in these larger tumors. It can cause some swelling, at least in the early few weeks. And we've actually had the same situation where we've had to take them out urgently because they're compressing the brainstem worse. So this tumor needs to be removed and personally, I think what I would do in this case is since there's so much the tumors are, do you have a T2 image here, Jim? Yes and you can see here that the T2 image shows a lot of oedema around the tumor. And I would approach this translabyrinthine at this point because the posterior FOSS is very tight and you'll be able to decompress that tumor very nicely from a translabyrinthine approach without causing any further worsening of the swelling and no retraction.

- Yeah we thought of this similarly, my feeling was going through the same incision. There would be scar tissue and there would probably be significant brain retraction to try to get this tumor out. Whereas if you look at the trajectories for a translabyrinthine you can virtually come pre sigmoid without any minimal to no brain retraction and decompress this tumor. So the question I have for you is in terms of your attempted extent of resection based on her already having radiosurgery, what are your thoughts in terms of your... what you'd like to achieve at surgery and how to deal with the facial nerve and potential tumor adherence?

- Sure, so I think there is a risk I approach every acoustic the same in that I try to go for a complete removal and that is tempered by obviously situations if the tumor is too stuck to the facial nerve and you think you'll sacrifice the facial nerve by dissecting it. So in a case like this, I would try to do a complete removal as I could it understanding and I would counsel the patient upfront that the tumor may be more adherent to the facial nerve given the fact that she's had radiosurgery, although the timing of radiosurgery was fairly recent and it may be dissectable. So I would make that decision inter-operatively that I would certainly counsel the patient that if we needed to we might leave just a small margin of tumor on the facial nerve, if it was too adherent and we were gonna end up sacrificing the facial nerve to get it out.

- So what we did was a left translabyrinthine approach, and we had an excellent decompression of the tumor. And there wasn't an area of tumor that I felt was very adherent to where it came out of the porous and so we left a thin remnant adherent to the facial nerve and she had an immediate Brachman 4 which improved to a Brachman 1 by six weeks and she did quite well and she was able to ambulate at at six weeks and even even better at three months. and here's a post-op scan you could see some remnant of enhancement along the nerve, and this has been stable for two years following up so far. So we'll be continuing to watch this over her lifetime and hopefully it won't grow further.

- Yeah she's been treated already with radiosurgery, so there's a good chance that residual will stay quiet.

- So here's the third case this gentlemen is a 38 year old male with left sided hearing loss non-serviceable and he already comes in with a very slight facial nerve palsy, but he didn't have any gait disturbance or imbalance. And here is his MRI scan.

- So this is an interesting case, a very large partially cystic schwannoma. You said that there's some facial weakness already, is that correct?

- Yeah.

- So you always need to consider the relationship of the tumor to the facial nerve in a case like this, but I would certainly go ahead and recommend surgery to remove this mass. And I think the fact that the patient presents with facial weakness, there's a little bit of a red flag and we'll have to carefully see the interface of the tumor from the facial nerve, but it's conceivable that the tumor may be more involved with the facial nerve in this case. So I would probably do this translab, but you could certainly do it retro sig as well. We used to have the adage that we would do the very large ones, retro sig. And I think it's quicker because you can see you'd get a bigger overall view of the size of the tumor and relationship to the brainstem and you can court quicker, but the advantage of the translab is there's no brain retraction and we'll remove tumors of all sizes translab at this point, although I think it would be a little bit quicker, obviously retro sigmoid, because you all, again, wouldn't have to drill the temporal bone and you'd have a little better perspective on the overall size of the tumor.

- Well I think we--

- What do we do in this case, Jim.

- The thoughts and considerations, you mentioned, went through our paradigm and I think given the size of this tumor, we felt that coming in translab would minimize the swelling and prolong brain retraction. We anticipated that this would be a longer case due to the size of the tumor and potential tumor adherence to the nerve. So we wanted to minimize prolonged brain retraction to the cerebellum we came in this translab and we were able to decompress this, and this was a difficult tumour. And I would appreciate your thoughts on your experience with cystic vestibular schwannomas since they can be a unique entity in treating these tumors.

- Yeah, there is literature demonstrating that cystic schwannomas can have a worse House-Brackmann scales after a surgical removal. I think the other thing that you need to consider in a case like this is that it's a very large tumor with a lot of expansion here along the base of the skull. So if you're gonna do this translabyrinthine you're gonna come in from this trajectory here, and you're gonna have a limited window, but what you need to do is you need to core the tumor as you normally do, and then start to bring the capsule in so that you're still able to come and dissect around the capsule, even though the approach is not giving you direct exposure here, you'll be able to shrink the tumor and then bring the tumor down. And then as you alluded to the interface with the facial nerve can be more difficult on these cases and the outcome would be worse and I would certainly counsel the patient to let them know that their face is really at risk in a case like this, given the size of the tumor it's cystic nature, and the fact that they have facial weakness to start with.

- So here's this temporal bone you could see the IC is quite expanded and the tumors, you wrote it into the features they picked you as well. And so we did this through a translabyrinthine approach. Here's the incision we made and here's the additional exposure and for a big tumor like this, we actually prefer to extend the craniectomy more posteriorly and get more retro sigmoid dural exposure. And what this allows us to do is we're able to have more mobilization of the sigmoid sinus so that we can mobilize it posteriorly to increase our operative window.

- I think that that's a good idea Jim you're deriving the benefits of both the translabyrinthine, presigmoid approach, and a retro sig into the same surgical corridor. I think that's a good idea and then you can move the sigmoid back and forth as necessary during the dissection.

- And so here's the tumor and it was quite soft. And at times hemorrhagic, and it's the nerve coming into view. I like what you mentioned about bringing the tumor in from the most medial aspect. One thing that we found is to get to that clival depression. You really have to do a good petrosectomy and make those trops above and below the IC. And then the nice thing about these vestibular schwannomas, as opposed to meningiomas is they're a little softer and you can bring them into your operative field. And so here's the sixth nerve and here's the basilar artery. And I must say this tumor was particularly adherent and here's the course of the nerve within the arachnoid. And then here's the abducens nerve and the nerve actually stimulated at 0.1 mA and I was anticipating a nice recovery of the nerve, but you did have temporary facial weakness that required a gold weight. It was a Brachman five, but fortunately at one year he did recover to a Brachman two and so here's the postop film. And I just wanted to briefly mention in terms of closure, at your shop, how do you like to close the translabs in terms of the petrosectomy master defect?

- Sure so nice job, Jim, this is a big tumor difficult case. So here's your fat graft I presume. This is a fat suppressed image and there's your sinus. Now I think when you take the bone off on both sides of the sinus, both pre sigmoid and retro sig, you've gotta be really careful about how much fat you put in the cavity. And this applies also to a regular translab. Because the fat itself can compress the sigmoid sinus. And so eustachian tube is plugged by the otologist. The fat graft goes in. We're careful to try and not compress the sinus too much with our graft. And then we usually put in a plating system. We'll use MEDPORE Dr. Shelton likes to use the absorbable plating system sheets, and we cut those as necessary. But I think it's important because this actually provides a buttress to your fat graft. And I like to use the MEDPORE it doesn't cause any depression at all post-operatively so they have a good cosmetic outcome as well.

- Do you use any postoperative CSF diversion, or lumbar drains in your approaches?

- We don't use it routinely, but if we do have an early CSF leak postoperatively, we'll put a lumbar drain in before we take them back to a repack with that, we'll try a lumbar drain for a few days. How about you?

- We prefer not to, we try to avoid using post-operative lumbar drainage to avoid any complications of intracranial hypotension. I just wanted to briefly introduce the closure technique that we've started to use for translabs, which has been successful for us. And what you're seeing here is this is actually a signal for an autologous fascia Lata. So in contradistinction to the traditional packing method where the dural defect is plugged with the fat down deep, and then brought up to the surface, we've been using the sling and I'll show you here in this illustration at the end of the tumor removal, we'll harvest a piece of fascia from either the thigh or the abdomen, and we'll secure it to the edges with interrupted sutures. And it makes sort of a sling. which suspends the fat graft. And we put an initial deep layer of fat to plug up any CSF egress and then put another superficial layer of fat to fill the rest of the mass to a defect. And we use our technique of the MEDPORE to buttress that fat graft. And also it's important to make sure that middle ear is sealed off. And if you do the eustachian tube packing method that's closed off as well. And so this is the interopt where you can see here's the tumor removal, here's the fascial sling, and we put the fat graft suspended. And of course we seal off the antrum and any air cells and then put the final superficial layer that we found good success in preventing postoperative CSF fistula using this technique.

- So I think that's a good technique, Jim. I think that the putting the fascial sling in with a big hole is a good idea. If you have a smaller opening, I try to cut my first piece of fat so it won't fall through the hole. And so I cut it in a sort of a torpedo shape. So, it plugs the hole and it stays in place and it achieves the same thing as the fascia sling. But I appreciate that on a bigger opening, having the fascial sling, there is a great barrier because there has been reported cases where people have caused a brainstem compression from a fat graft and we've certainly had cases as well, where we've compressed the inflow of the sigmoid sinus with too much fat and I've had to remove some of that So a good technique, but one comment, because I don't know whether we're gonna show up a middle fossa approach, but closing the middle fossa is tougher because you don't close off eustachian tube yet the air cells are usually violated. And so we'll place a fibrin glue and then fat graft in the area to try and seal those off.

- Great points, Dr. Couldwell, let's change a little direction here. This is a 60 year old male left sided of hearing loss with gait ataxia and with this scan.

- Sure, so this fairly straightforward, I think it could be done retro sig quite easily, or translab either way would be fine. I don't have any personal preference on this one. There's not much in the canal. It looks on these images do you have more images, Jim?

- Yep.

- Great, yeah. So there's a tumor, a little ways in the canal. I think it could be done retro sig or translab, I think is dealer's choice.

- So I agree with you on this one and we decided to do retro sigmoid on this, and I believe this positioning is very similar to what you do for retro sigmoid and if you could just comment and take us through on how you position and make the skin--

- Sure I like the lateral position for the sole reason that it reduces the turning of the neck for vertebral artery and also the outflow of the jagular venous drainage. It's important to pull down the shoulder and get it out of your way. And then the skin incision that I use similar to this, I use a little smaller one because we do the retro sig through a fairly small opening about a 50 cent piece, just perfectly located. And so I use a little bit smaller incision and otherwise very similar and keep the head in this relative position in space, obviously facial nerve monitoring, and I pull the ear forward out of the way. And so I think you've got most of the elements here of our approach.

- And here's the postop scan, and we got a nice tumor removal with a nice facial nerve result on him and--

- Excellent.

- How about a case like this little bit bigger tumor, dizziness and vertigo, and he's already got non serviceable hearing, but a normal gait.

- Yeah, I would remove this translabyrinthine. There's a lot of tumor in the canal. It's perfect in my mind for a translabyrinthine approach and he's got vestibular symptoms. I certainly believe that this would helped probably with removing this surgically. So I would offer him surgery at this point. I know many people would offer him radiosurgery. I presume this is less than three centimeters.

- So here are the temporal bone CTS. You can see the canal here is widened and the coronal scans. So in terms of the approach, our first thought was a translabyrinthine just as you said, and what we've been doing at our shop is we've been using the temporal bone CTS and creating a virtual dissection model on the dextro scope, virtual reality system. And my otologist likes to do these and we explore various approaches before choosing a definitive approach. And so when we went through this exercise, we felt that the translabyrinthine approach, we had difficulty visualizing the most medial aspect of this, and obviously in a soft tumor, we can bring it into the field. But when we came and looked at it on the virtual model, retro sig, it just felt that we had a more straight shot to visualize and access the region of the tumor at the clival depression. So hearing was not an issue in this case, but based on our exercise and using the virtual reality system that we have in our hospital, we felt that the retro sig would be easier for us. And that's how we ended up choosing a retro sigmoid approach and this is the positioning that we've discussed before, and we achieved an excellent result and he had a normal facial nerve function immediate post-op.

- So that's a good outcome, Jim, just one comment. So when you come in retro sig, and you've got a situation where the tumor's out in the distal end of the canal here, we'll use an endoscope to visualize that tumor and make sure that we remove all of that because you don't have a direct vision to look at the the distal end of the fundus of the canal and a side angle endoscope of 45 or 70 degrees is just perfect for that. So just a little tip that we'll plan to use that on a retro sig in a case like this.

- That's a very good point, Dr. Couldwell, I think the, the use of endoscopes in the CP angle for that reason is a very useful adjunct. If you could just comment, there are some that advocate direct CP angle surgery, purely endoscopic. Is that something that you would recommend and do you think there's any gains or advantages of doing that as opposed to having a purely microscopic approach?

- Great and so I think that's a good point. I do think there's some advantages to the endoscope. The disadvantage that you have with the endoscope is an issue of surgical fidelity. And I think it's akin to trying to write your name. And I think Sam MFT has used this as an analogy, but I think it's a good one. If you hold a pen and you try to write it using... hold it by the end of the pan, you don't have the same dexterity as if you hold the pen in the usual fashion. And I think it's a similar issue when you're using the endoscope, because you have an endoscope in the way, and then you don't have the same tissue plane dissection technique that you use with common bimanual microsurgery. Now where this may be a game changer is with a 3D endoscope, with a ability to park it in the corner of the field and use the 3D endoscope as a microscope. And I firmly believe that that technology will achieve all the benefits of the standard microscopy operation without giving up excellent bimanual technique. But those are comments that are more relevant than I made for transfacial surgery. But they're also important when you're using an endoscope in the posterior fossa, because you don't often have room for an endoscope and two hands to operate.

- Great, thank you, I appreciate your thoughts on that topic. Let's go ahead and move on to the last case here. This is a 38 year old female. She has mild to moderate hearing loss, but very good serviceable hearing tinnitus and vertigo, and then she's otherwise intact. So how would you go about this? Would you observe her radiate her or offer her surgery? And if so, what approach?

- Certainly, so this is a interesting case, and we see these tumors quite frequently, smaller tumors with some vestibular symptoms. And I think obviously there's three options here. You could observe, you could remove the tumor or you could offer radiosurgery my personal preference on a 38 year old female would be to offer her the option of watching this or moving it. And the reason that I would prefer to remove it rather than offer radiosurgery in this case is that she has symptoms. And if she's disabled by her vestibular symptoms, you can help her by removing the tumor. And she's not getting a changing vestibular signal and function over time. And they tend to evaluate very quickly to the loss of stupider nerve on that side. And then they get over their distributor symptoms. But I think observing this patient is fine. You'll have to counsel her that you'll likely lose hearing on the right with time. And many patients may choose that as well. So I think three options, a case to be made for all three. My preference in this case would be to observe or remove given your age and the symptoms that she has.

- So we, we had the same discussion with patients and given, her young age, and also you are right about the, the vestibular that was a big components for her. And so we offered her surgery with a hearing preservation as one of the goals of surgery. And in terms of a hearing preservation approach, what'd you do this one middle fossa or retro sigmoid.

- So I think this one in particular could be done either way, Jim. The tumors halfway into the canal. I think you could safely remove the posterior lip of the need is here and without getting into the semicircular canal and remove the tumor quite easily, retro sig, the other option would be a middle fossa. So the middle fossa is a beautiful approach because it puts you right on the canal. And it's all the exposure that you need for a tumor Like this is just the canal. The disadvantage of the middle fossa is that it requires temporal lobe attraction. So that weighs in whether we're considering retracting a dominant temporal lobe versus a non dominant such as in this case so I think a middle fossa on the right side would be fine here also retro sig. So I think it's dealer's choice on this one either way would be fine. The only other comment that I would make about a middle fossa approach is that the only disadvantage is it, the facial nerve can lie right on top of the tumor and can be right in your way when you dissect the tumor. But it's usually not a problem if you remove the tumor and debunk a little bit, you're able to mobilize the facial nerve off of it and then remove the tumor. So we would probably do this middle fossa, but I certainly think retro sig would be very simple to do here as well.

- I agree with you, Dr. Couldwell I think, both approaches wouldn't be fine for this tumor. We ended up choosing retro sigmoid approach only because the tumor was in the proximal to mid IC rather than all the way lateral into the fundus had the tumor been out lateral here we would have chosen the middle fossa, but we felt that the retro sigmoid here in this particular case would allow us to do retract or list surgery and not involve any brain retraction to get this tumor out. And we're also able to avoid temporal lobe retraction as well in the middle fossa. And here's the inter-operative picture so we're not using a fixed retractor, but just merely using dynamic retraction as Dr. Spencer had described in this paper earlier this year. Using the suction to intermittently mobilize the cerebellum. And so here we are taking the dura off of the petrous bone at the lip of the porous and we're drilling out the IC here. And once we open up the IC, we can find the arachnoid Plains and dissect the tumor off of the facial nerve. And the one reason I liked the retro sigmoid if we can do it retro sigmoid is that the facial nerve is behind the tumor and the cochlear nerve is and behind the tumor. Whereas just as you mentioned in the middle fossa, there are some cases when you come middle fossa, the tumor can be below the facial nerve. So the facial nerve is between the surgeon and the tumor, which can make it somewhat of a challenge. And so here's the final removal of the tumor and here's the nerve being stimulated and it stimulated at 0.05 mA. And here's the cochlea nerve , and we were able to preserve hearing in this case and the vestibular symptoms improved significantly. So we were quite pleased.

- Great job, Jim looks good.

- Now, what do you do at the porous? You we'd like to put a little... we wax off the air cells and we put a little fat graft in the defect, but we're careful not to put too much fat as you mentioned before. What do you like to do handling the porous?

- Sure, so we do the same in that we carefully look with an endoscope to see if any of the air cells of the pitrous bone have been violated. And then we wax directly under vision with an endoscope. And then I usually lay a piece of muscle and I just cut it just to avoid another incision for fat harvest. And I usually lose just local muscle suboccipital muscle, and then place that in place over the defect and then place fibrin glue to hold it in place. But I think a using a fat graft is very reasonable as well.

- Well, thank you very much, Dr. Couldwell, great discussion and thank you for your pearls of wisdom. And this concludes our September issue, podcast for Acoustic Neuroma.

- It's a pleasure to be involved, Jim, and it's an honor to do this with you, thank you.

Please login to post a comment.