Grand Rounds-Transpetrosal Approach: Indications and a Video Review of Cases

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- Hello, ladies and gentlemen. This will be part two of the discussion with Dr. Nick Bambakidis which we'll review sculptures approaches for regions along the middle and posterior fossa. Again, thank you for joining us.

- Well, I just wanted to talk a little bit about the petroclival tumors and show a few cases because some of the technical considerations in terms of the approach are similar... Approaches are similar to what we've discussed with posterior circulation. Aneurysms, in terms of petroclival tumors, I tend to use the IAC and the tentorial edge as important landmarks in helping to determine what kind of surgical approach do you utilize. I think the retrosigmoid approach is still a workhorse for many of these tumors. I'm more likely to use petrosectomy in cases where the tumor is entirely medial to the IAC, spans the superior... Spans the middle and posterior cranial fossas or in cases of diminished hearing non-dominant hemisphere. Younger patients where I really want to do an aggressive resection. Those are really my considerations for when to use a transpetrosal approaches. Aaron, do you have thoughts regarding your indications for utilizing those?

- I agree with you 100%. We have been using the antipetrosal or posterior petrosal less and less as we can see how much you can push the limits of the retrosigmoid approach and if necessary cut the tentorium through a super cerebellar approach to really reach the tumors that are more laterally located. So if you have a tentorial tumor that really spans above and below the tentorium, I think cutting the tentorium may be very reasonable. But if you have a clival or mainly a petrolclival tumor with mostly a clival shorter segment. You probably are forced to do the posterior petrosectomy especially if it is located among along the middle third of the clival space. Just to be able to see the space, identify the vasculature and preserve them. Because the last thing you want to do is shortcut the patient by putting them through a retrosigmoid approach, not be able to see around the entire brainstem adequately especially along the mid third of the clivals pool on something and then also perforator.

- Right, I think those are very important points. So here we have a 50 year old female with facial pain and numbness. Here we have this presumed meningoma spanning both cranial compartments, a very significant portion of those tumor is in the middle, cranial faucets entirely medial to the IAC. It's right-sided lesion and so in this case, this is a case in which we utilized a right-sided transpeter's approach using hearing preservation. Can we start the video, Aaron? This is a case where I'll do in collaboration with Dr. Cliff McGahren who's our neurotologists here at University Hospitals and typically I'll do the craniotomy. Again, this is on the right side. The middle cranial fossa, posterior cranial fossa. He's drilled off the presigmoid space preserving hearing and here now open the presigmoid space and cutting the tentorium. I think for folks who are learning how to do these procedures categoric exercises are critically important. Here's the fourth cranial nerve, which you want to identify medial to the tentorial edge before it's divided. Here's the SCA below the fourth cranial nerve here. So now you've essentially span both cranial compartments and can easily access them in addressing this tumor. So here's the subtemporal portion of the exposure here, dividing the tentorium, and here's the fifth cranial nerve here. And here's the tumor now. And, of course, the most important consideration in any of these cases when you're talking about what approach to utilize is really the consistency of the tumor itself and its adherence to the neurovascular structures. And if you have a soft tumor really that's more important than the approach you decided to utilize. But in this case here, you see the basil artery deep to the resection and the tumor coming out quite nicely. So once you we've done the middle cranial fossa portion of the operation, and, again, here's the basil artery, ICA perforators coming out of the brainstem. Nicely visualized and protected. You can then move to the inferior cranial portion, the posterior cranial fossa part of the operation just around the petrous ridge and remove the rest of the tumor here. The IAC is down here underneath the section. Aaron, do you have any other thoughts?

- [Aaron] No, I think this is very well done. Obviously, the IAC is the landmark for differentiating your need for anterior versus posterior petrosectomy. This tumor just went barely below the IAC, and you may have considered just anterior petrosectomy to be adequate and using a coasit triangle through the middle fossa to resect it. But I think this is very reasonable. You're showing the beautiful anatomy of the posterior fossa. I'll let you go through that and I'll make one comment at the end of this.

- [Nick] All right, at least you can see the spanning both compartments here nicely. And I think your point is well taken. I think you could probably consider that as a nice alternative to doing this procedure.

- [Aaron] I think if we go back to the slideshow and review the MRI on this one, you can see this tumor just comes below the IAC. So I think it's reasonable to use petrosectomy, posterior petrosectomy but I think an anterior petrosectomy may also be a reasonable option. The other nuance that I have come to realize is that the fifth nerve where it enters the tentorium, where you're cutting the tentorium, you have to be very careful because it can be very variable. Some of the fifth nerve in-patients enters the tentorium earlier and if you're just cutting blindly, especially in anterior petrosectomy approach, you will injure the fifth nerve. The other nuances, don't be too aggressive with tumors that are very adherent to the fifth nerve. The significant numbness associated with the fifth nerve can be very, very disabling. So, again, in a benign meningoma there is no reason to sacrifice function if you have to leave a little bit of tumor behind over the nerve. And I can see this as a beautiful job with a very nice postop MRI.

- Yeah, I think those are very, very important points. This is another example. This is a 63 year old man with a sudden onset of hearing loss, a complete hearing loss and facial pain similar to what you've mentioned and here you see this heterogeneous lesion extending down into the petrous apex. Here, irregular enhancement blood products within it, extending down to the CPE angle. You can see here the bounty destruction, see how inferiorly it extends here. You can start the video. So in this case, again, we have a right sided non-dominant lesion medial to the IAC extension at the posterior cranial fossa, a very deep petrous apex. And with complete loss of hearing, so in this case, we can be more aggressive in the petrosectomy with Dr. Magarian assisting me. We're performing the craniotomy. I like to, again, do this first. It makes the petrosectomy much quicker in our experience. And so here's the sigmoid sinus. I'm very aggressive in taking all the bone off of the sigmoid, again, opening the pre-sigmoid duran as opposed to the previous case where there's still because of our effort to preserve hearing significant part of bone left in the petrous apex. Here we were more aggressive in giving us a better exposure. And, again, this is a another example of cutting the tentorium preserving... Here you can see the veinule bay quite nicely and dissecting it sharply, taking your time away from the dura. It's critically, critically important to preserve those venous structures. I'm sure you agree, Aaron.

- [Aaron] I cannot agree more.

- [Nick] And so here in the petrosal sinus usually I use some wet clips just to divide that, just to expose the tentorium and cut along it. And, again, identifying the edge of the tentorium and there is a fourth cranial nerve. So you always want to see that before you complete areas there. You always want to see that before you finish the tentorial incision SCA here, PCA here. There's the SCA, PCA, and the posterior faucet there. So now here, this tumor as opposed to the other one, as Dr. Cohen mentioned, this one has extensive involvement with the posterior fossa. This is the IAC and the seventh and eighth nerves, and a lot of blood products here. This turned out to be a congress sarcomas. You may have guessed from the preoperative imaging. And so we really wanted to get a good resection on this gentlemen to give him a good long-term result. So you can see here working around the seventh and eighth nerves, the fifth nerve up here and taking out all of the tumor within the CPA there and then moving around to the petrous apex. This involve the petrous apex extensively. So we did an anterior petrosectomy and really encountered tumor right away. I hear cutting the tentorium up, preserving the fifth nerve and getting right into tumor almost right away. So it really is inside the petrous apex and cleaning that out as best we can. Do you have any other thoughts, Aaron?

- [Aaron] No, I think it's a beautiful case. A very great example of the technical analysis for this very difficult skull-based approach. Obviously, in this chondrosarcoma maximal resection is very helpful. And so you keep that in mind. I think as you'll see in this post-operative image, it shows a very clean resection neck and a spectacular job.

- Yeah, I put this case in here just to show an example of an acoustic neuroma. And I'd be interested to get your thoughts there and how you would treat this. This is an 18 year old male with hearing loss, a complete hearing loss facial, not unless you can see this very large acoustic tumor. Now, I think certainly a lot of options are available for treating this. How would you handle this?

- I would definitely proceed with a surgical resection. The hearing, I think, at this junction most likely as you said, is very much affected. So my personal preference is really the retrosigmoid approach although the translab approach would be also very appropriate. So I think that's a dealer's choice. Usually, that really depends which department they come from. If they come from ENT, we may use a translab approach because they like that. And if they come through neurosurgery, we use the retrosigmoid approach. The preference of a neurosurgeon is such a challenging and big tumor in a young person, which where the brain is very full. That's the challenge that I have run into. When the patient is so young, Nick, retracting cerebellum can be very challenging to go and see the more medial part of the tumor along the middle cerebellar peduncle. So in those situations where you really need the least amount of retraction on a very young cerebellum that could cause intra-operative significant malignant swelling, I would say the translab approach maybe preferable.

- Yeah, and I can tell you that's exactly what our thoughts were and I think that it's interesting as your career proceeds, your evolution, your preferences, and you experience in doing these kinds of cases. So in this instance, Dr. Magarian, gave us a wonderful exposure in doing sort of a really extensive trans-labyrinth thing approach and I think that if you're gonna do it for the large tumor like this, I like to get all this bone off, the sigmoid sinuses and even expose some of the middle cranial faucet. It gives me enough room because that's really... That's really what we like about the retrosigmoid approach, isn't it that you're not limited by the exposure in any way for these large tumors. But I think here because you really come right down onto the tumor with this approach. It's really very nice. Here's the pre-sigmoid dura here and really coming right down onto the tumor. Here's some of the cerebellum and barely you have to do any manipulation of the cerebellum and we can see how full it is. Again, as you mentioned in a young person, how far that cerebellum is and I did... I went ahead and divided some of the tentorium just to give me a little more exposure to the top edge of the tumor. I don't think it's... Certainly, I don't think it's necessary in most cases, but I think it does limit the amount of pulling that you're doing over the top edge of the tumor and you mentioned some of the risk to the SCA perforators that can occur when you're reaching over the top of these large tumors. So here we went ahead and just cut this portion of the tentorium just to give us the best superior exposure that we could get in this case. And once we did that really it's the same technique that we all are familiar with in debulking these acoustic tumors initially, and generous use of the facial nerve monitor throughout the procedure to identify the nerd course early. So here you can see now the tumor really is right here. So you're really working right on top of it throughout the operation. Do you have any other thoughts, Aaron?

- No, I think that this is very fair. I have recently done a six centimeter acoustic on an 18 year old woman and at that juncture, we decided to do a reterosigmoid approach and did have intra-operative swelling. It wasn't bad enough, we were able to do what we needed to do but it was definitely a learning experience that in these young patients, the swelling can be a significant factor and you should consider what you're doing right now. And for acoustic surgery in general, the most important way for you to increase the efficiency of your procedure is maximal debulking. Be extremely aggressive with debulking the tumor. You'll find that it will be a lot easier to handle it. Go ahead, please.

- [Nick] Right there is the seventh nerve there you can see a very typical location for the seventh nerve coming around the inferior pole. Of the tumor, I agree the amount of debulking is critically important in safely getting these tumors out. You can see the seventh nerve in the IAC there. So here's the seventh nerve, of course, right there, beautifully preserved there. And I personally do not believe in a strategy of subtotal plan, subtotal resection followed by radiosurgery especially in young patients. I'm guided by the interoperative anatomy and findings and we'll typically plan for gross total resection and cure especially in, again, in young folks. I don't know what your thoughts are, Aaron, regarding that.

- I agree with you 100%. We don't plan subtotal resection, however, we are very lenient in terms of leaving a piece of tumor special in a young girl whose face is so important to her. And so if we feel that the tumor is very adherent where the nerve interests pours acoustic, we do leave a small sheet of the tumor, we do not do radiosurgery routinely afterwards. We do regularly follow up MRIs and if there is evidence of growth, we'll go ahead and proceed with radiosurgery. But if the tumor is adherent, we do leave a piece of tumor to save the face.

- So this is our last case discuss here. This is a 45 year old man with progressive hearing loss and now with a facial weakness, House Brachman Grade III on presentation. And you can see this, a large dumbbell shaped tumor, again, spanning both creating a faucet extensively going through the porteous apex. And so in this case with no hearing and facial nerve weakness, I thought the best approach would be a transcochlear approach to resect this tumor, which turned out to be as we would have guessed from the imaging and findings that facial nerve neuroma. You can see here that a craniotomy, a middle cranial fossa close to your cranial fossa is typically how I do these moving the bone, sigmoid sinus, transverse sinus, and here exposing the middle cranial fossa portion of the tumor, which was mostly extra dural with a thick capsule. And so that portion of the operation is very straightforward. Here, Dr. Magarian is drilling out the petrous bone completely removing the cochlea. Here, you see tumor within the petrous bone involving the geniculate ganglion and the course of the facial nerve. And so all of that was removed. And, in fact, during this operation, he oversewed the ear canal and closed it completely. Here you can see now a complete extent of bony resection opening. Again, the tentorium here working in the pre-sigmoid space, there's the clips on the dorsal sinus now. Here's the cerebellar surface here. Okay, temporal lobe here. He's cutting the tentorium fourth nerve. Again, you notice in each case, we've shown how important this is in preserving that for the fourth nerve there. There it is. And so now, again, with all this bone removed you really are working right on top of the tumor here. Here's a fifth nerve, fourth nerve. Okay, dissecting the tumor away from the fifth nerve. Here's the basler artery, ICA, perforators. IAC is down here. Here's the sixth nerve over the top of the basilar artery. You can see how beautiful here at the exposure of the basilar artery here. It's really a right on top of your field. And so once you've identified those important structures, it's a matter of debulking the tumor. You can see the expansive view you have when you're done with the entire porteous bone essentially drilled out almost down to the carotid canal on the basilar artery at the bottom. And, of course, closure is critically important. In this instance, we use a lot of fat to pack the area, titanium mesh, and lumbar drainage post-operatively to manage potential complications. Do you have any thoughts on that? I guess, Aaron, how you would have handled that differently?

- It think it's very reasonable the way it was. We would have done this. So in my question is how did you guys manage the facial nerve? You say it's a facial nerve neuroma?

- During the same hospitalization, we went ahead and did a hypoglossal facial nerve anastomosis. He essentially had a rapid progression of loss of facial function over several months. I hope this that he'll get back to at least a grade three sort of facial function over a year or two.

- You use this motor evoked potential monitoring and SSEPs in these cases, Nick?

- We use SSEPs, I even found motor evokes to be particularly helpful in these cases.

- I agree. I agree with you. The only other option, although I would have never done it that way is to stage these and maybe remove anterior fossa in one stage and come back to the posterior fossa. But, again, I think that limits the view you're gonna get around the petrous bone, which you very eloquently illustrated. So I really think this is a very versatile approach and if you're comfortable with it, it really works well for the pathology you just used for.

- And that post-operative images really just show you how extensive the body resection is. And, yeah, this isn't the kind of case where you... We don't use these approaches lightly. I mean, there's specific indications, I think and I think the was... That's sort of the message I think we want to try and get it across. Well, with that, I think we concluded our case presentation and thank you for having us, Aaron. I appreciate the opportunity to participate.

- Well, Nick, I want to thank you very much. Again, really a masterpiece of surgical cases. Obviously, one of the most... Some of the most challenging cases we face in our surgery and cranial surgery every day. If I may add, the top three lessons we learned from these very difficult cases is I think just appropriate selection of the corridor, how to approach deletion cannot be emphasized. Even over that, my experience has been as the surgeons adaptability to pathology. You let the pathology dictate what is the right and safe thing to do. You cannot use the surgeons ego as the way to dictate how the pathology should act to protect the important neurovascular structures. So you have to have a wide exposure if necessary, but you have to handle the pathology as it comes along and as it makes the surrounding structures very safe. And, also, I think most important, the last lesson is preserve every vein, every artery, and be extremely patient. Nothing is really spare in there, in that region. I guess everything is supposed to have a function for it. Any other thoughts on those three lessons?

- No, I think that those are really, really great points to add in dealing with these tough cases. So I hope folks pickup at least a smattering of tips to utilize in dealing with some of these tough challenges.

- Thank you, Nick.

- Thank you.

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