Grand Rounds I: Conquering Technical Challanges in Tumor Surgery

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- Hello, ladies and gentlemen, and thank you for joining us. We have Dr. Bill Couldwell as our guest discussing today, sharing some of his challenging tumor cases and the associated pearls of technique. This is a very exciting session, full of amazing cases with great learning points embedded in each of them. We hope you enjoy these sessions and again, thanks for your time.

- Well, I'd like to present a few challenging tumor cases with some technical pearls that I've learned over the years. First case is a third ventricular tumor. You can see that it is wholly within the ventricle. It's important to recognize in this case, that the pituitary stalk is coming out directly inferior, so I felt that the tumor was wholly within the third ventricle. And so, instead of approaching this through pterional or orbitozygomatic approach, we're approaching it through the ventricle, so transcortical, microscopic and endoscopic removal through the foramen of Monro on the right side. The tumor was firm. We were morselizing the tumor, and then removing it in a piecemeal fashion. We were taking great care not to manipulate the fornix. This was a rare case of a third ventricular craniopharyngioma that was completely within the ventricle. And we're dissecting the walls of the ventricle off of the tumor and carefully mobilizing the lateral walls of the tumor to enable us to visualize and remove it. At the end of the dissection, I left the ventricular catheters in the third ventricle, she's had a complete removal. This was craniopharyngioma. This is a vestibular schwannoma that presented in a 42-year-old woman with significant hearing loss. Since she had profound hearing loss, we weren't concerned with hearing preservation in this particular case. She's got a moderate size acoustic tumor involving both the cistern and then expanding the internal auditory canal. So we'll perform a translabyrinthine removal in this case. And I have the pleasure of working with a superior otolaryngologist, Dr. Clough Shelton who's starting the drilling here. The external auditory canal is visualized here and he will drill the mastoid leaving the wall off of the external auditory canal, identifying the sigmoid sinus, in this case, the sinodural angle, middle fossa dura, and then drilling the labyrinth directly. The facial nerve is running in the canal here in the fallopian canal. Plugging the eustachian tube with some bone wax and Surgicel through the middle here, just above the facial nerve. So now we're exposing the seventh nerve in the fundus of the canal. The vestibular nerves are cut. This gives us a beautiful visualization of the seventh nerve early in the dissection. We open up now the dura over the tumor in the cistern and we're now dissecting the tumor off of the nerve in the internal auditory canal. We go ahead and debulk the tumor. This then will allow us to mobilize the capsule of the tumor and dissect it off the brainstem and the nerves. Identify the seventh nerve of the brainstem and then proceed with our extracapsular dissection around the tumor and off the brainstem. This is done carefully with fine micro Cottonoids. Again we do a repetitive process of debulking the tumor and then dissecting the capsule. Now we'll identify the seventh nerve on the back of the tumor, and you'll see you use great care using micro dissectors to dissect the nerve off the tumor in this plane. Here's the seventh nerve. We'll do this with the online seventh nerve monitoring and identify the seventh nerve both proximally and distally and work the tumor off of. Here's the seventh nerve. It's a careful dissection identifying arachnoid adhesions, making sure that we find the perfect plane between the tumor and the nerve. Ultimately, we reduce the attachment to its smallest and disconnect the tumor from the nerve in the cistern. We stimulate the nerve at 0.05 milliamps to identify and to assure that the nerve is intact. We'll proceed with closure. Fat graft is placed in the mastoidectomy defect and then we use an absorbable plating system to cover the bony. So this is a 63-year-old woman with headache and blurred vision. She felt that she had vision loss in her right eye. On neuro-ophthalmological evaluation, she had a partial third nerve palsy and this strategically located skull-based meningioma just over the lateral and superior aspect of the cavernous sinus. And it was also about in the optic nerve on the right side. So we'll perform a right fronto-temporal approach in this case and split the Sylvian fissure widely and identify the tumor and its attachment. And although this is not a big tumor, it's located right at the base, and we're gonna be very careful with our dissection off of the neural and vascular elements. So here's the lateral aspect of the tumor, the right optic nerve in this location and we're starting to debulk the tumor. This then affords us the ability to do an extracapsular dissection after we've removed the center of the tumor and we'll slowly dissect it off of the carotid artery and the optic nerve. I think this is a good case 'cause it demonstrates that it's really the arachnoidal adhesions in these tumors. So when dissecting it off the optic nerve in this place along the lateral aspect of the optic nerve, we're carefully identifying the arachnoidal adhesions and cutting those, Here's the right carotid artery now. And it's a similar technique, we're rolling the tumor off and dissecting it directly off of the artery and identifying the point of attachment and sharply dissecting this. Ultimately, the attachment of the tumor was on the dorsal and lateral aspect of the cavernous sinus, and you'll see us identify this and then cauterize the attachment directly and remove the tumor. The third nerve is left intact.

- I have a question, Bill about these cases that sometimes haunts me personally. When you have a tuberculum sellae meningioma for example, when the nerve is very attenuated and you try to do your best even when you sometimes do the slightest manipulations, the vision seems to get worse, especially when the tumor has really caused a lot of thinning of the optic nerve. Do you have any pearls of how to handle these already compromised optic nerves in order to prevent additional injury while you remove the tumor?

- Right. So I think it's important on these cases and it's when I do aneurysms as well, is I like to decompress the canal and get the pressure off the nerve as early as possible in the case so if it's a tumor, I'll gut the tumor and try to decompress the nerve indirectly. And if it's an aneurysm, I'll open the canal is the first thing I'll do and then it allows the nerve to shift over and takes the pressure off the nerve. And then when it comes time to dissect it directly off the nerve, the nerve is not under tension anymore, and I'll do it under direct vision and just like you saw there, every little attachment gets sharply cut. So I don't do any blunt dissection at all along the nerve, I do sharp dissection. And Dr. Fukashima, I mean, he had vowed never to use blunt dissection and I think it's a very wise thing because it avoids any kind of pulling and tension on the nerve when you're trying to decompress it. So that would be my only suggestion.

- Thank you.

- So I'd like to present a 36-year-old young man presenting with neck pain and numbness in his right upper and lower extremities. He had an MRI which demonstrates a foramen magnum meningioma, predominantly midline with a little bit of left bias. The left vertebral was much smaller with marked brainstem and surgical meningiary compression. So we'll perform a left far lateral approach in this particular case. The sinus is drawn. The incision extends down to C4 in a curvilinear fashion up to the region of the sigmoid transverse junction. The key in this approach is to identify the transverse process of C1 early on in the dissection. And this is easily palpable just below the mastoid tip because this is where we'll dissect down and all the muscle medial and posterior to the transverse process will come and be reflected posteriorly. This gives us a good exposure to the retrosigmoid area, the mastoid, and C1 in the vertebral artery. The vertebral artery is identified, again in its relationship to the transverse process of C1. And it's identified as it runs superiorly in the vascular channel of the C1 lamina. Here, we're now starting our bony removal. This is done with a high-speed drill. And we'll identify the posterior aspect of the condyle and drill down through the foramen magnum. It's important to remove the foramen magnum and the lamina of C1, taking care not to injure vertebral artery as it runs in the vascular groove. We're drilling the posterior aspect of the condyle now, and we'll open the dura along the limits of the sigmoid sinus down to the region of the jugular bulb and just behind the vertebral as it enters the dura. Immediately we're upon the tumor, you can see spinal accessory nerve, which we're taking much care to retract out of the way and the tumor is attached to the dura along the anterior lip of the foramen magnum. This is a very tough tumor in consistency and requires both the CUSA and piecemeal removal by cutting the tumor. We're dissecting the tumor carefully off the brainstem, taking care not to injure the spinal accessory nerves and the lower cranial nerves. And once again, this process of debulking the tumor, removing the tumor from the center, and then doing an extracapsular resection and dissection. Here we're removing the attachment of the tumor along the base of dura. Got to be very careful in this case not to give the patient bilateral cranial nerve palsies. So this is a case of a middle-aged woman with a very large petroclival meningioma and brainstem mass effect that's gonna be seen here on the ponds. She has some diplopia, some facial numbness, and we'll perform a subtotal resection of this and leave the portion of tumor within the cavernous sinus proper, remove all the tumor, pushing on the brainstem and decompress the optic nerve as she's losing some vision via visual field examination, use the lateral position, pull the arm down. Here's our flap. Since we have to decompress the optic nerve, we'll perform a trifossa flap in a very large craniotomy, and then perform a transcochlear approach as well. This is Dr. Shelton performing the mastoidectomy. And here, we're drilling out the fallopian canal. Fallopian canal is in this location, plug the eustachian tube. After the mastoidectomy is performed, we'll perform a craniotomy. And as I mentioned, this is a trifossa craniotomy to enable us to decompress the optic nerve as well as remove the posterior fossa and the middle fossa components. The L-shaped flap, we're on the back of the mastoidectomy. The craniotomy has been performed in this case and we'll go ahead now and Dr. Shelton will complete the drilling of the petrous apex. We'll perform the pair petrosal approach, combined petrosal in this case, open the tentorium and this provides access to the posterior fossa and the middle fossa tumor. We'll start with removing the middle fossa tumor here, through the middle fossa up to the lateral wall of the cavernous sinus. Then we'll perform an optic nerve, an optic canal decompression given the fact that she's got a visual field deficit. Right-sided frontotemporal approach now. Decompress the optic nerve, remove all the tumor around the optic nerve, carotid artery, and the third nerve. The third nerve is associated with diplopia in this case. We'll adequately decompress this in the cisternal segment and open up the roof of the cavernous sinus to decompress it at its foramen. We'll remove tumor lateral and medial to the ocular motor nerve. We'll then raise a flap over the clinoid and drill the optic canal proper. Tumor is involving the region of the optic canal and we'll make sure that we've adequately decompressed this by removing the clinoid and drilling the canal all the way to the Annulus of Zinn. Opening up the optic nerve sheath and removing any tumor in the canal. We'll now perform our posterior fossa resection and remove tumor, optimizing the ponds. We'll work between the corridors of the fifth nerve, the seventh and eighth nerve and then we complete our resection and perform our closure. We replaced the craniotomy, place fat within the mastoidectomy defect.

- So Bill, if you don't mind, I would like to run this case by you. A 42-year-old male with a progressive history of gait difficulty and recent onset of dysarthria. He underwent MRI evaluation which revealed this homogeneously enhancing mass along the mid portion of the tentorium as you can see extending below the IAC also very much into the region of the middle fossa sort of spans both spaces and really offers special challenges in its resection. What made this more complicated was that this lesion was very much vascular, as you can see. And before I go further, I'm interested in your opinion about what are the approaches for resection of such masses?

- Sure. So this is a challenging case, as you are aware. This man has a significant tumor, both above and below the tentorium. So this could actually be done by probably three different approaches, but one would be a combined petrosal approach, which would include a supratentorial and infratentorial approach. A posterior approach, which would encompass basically coming in from below and then opening up the tentorium and then removing the tumor. And the third approach would be an anterior petrosal type approach, which Professor Colossi of course would perform and this would come in basically subtemporal and then remove the tumor at the apex here of the petrous bone, drill the apex, which will then visualize the inferior portion down in the posterior fossa. Personally, I would probably perform a combined approach on this to remove this tumor, to have access to both the superior and the inferior part. The key to this approach will be to be very careful with the trochlear nerve. The fourth nerve will be running adjacent to the tumor, possibly within the tumor just prior to its entrance in the edge of the tentorium, and the key will be to try and preserve that nerve during the dissection.

- That's exactly what we're thinking and other colleagues of mine who looked at this tumor, the trochlear nerve is especially important for this man because he's a truck driver and obviously double vision is gonna be a significant side effect, adverse effect of the operation. I'm gonna go ahead and show you Bill, some of the other sequences, the T2 sequence as you can see reveals a really high vascularity of this mass with maybe very mild marrow edema along the brainstem and an angiogram which was performed before this patient was referred to me really reveals a relatively hypervascular tumor, mainly by the arteriovenous along the tentorium, and really there wasn't much they could do. And this really has been our practice, that we do not embolize meningiomas anymore. As you have mentioned to me previously, I think the gain is too little compared to the risk and I think meningiomas can be so easily devascularize along the base that really embolization doesn't play a major role in their management. What are your thoughts there?

- Yes I mean, some years ago, we did a number of embolizations for these tumors. More recently, we've gotten away from that because we feel that the risk benefit ratio is not worth trying to embolize. They're often difficult to embolize, and so we just now proceed without embolization on almost all the skull-based meningiomas because each one of them has risks regarding the location of embolization. In this particular case, you will have to embolize right off the internal carotid artery, as you can see.

- I agree. And here are really what you very eloquently summarized when you looked at this case. Extended retrosigmoid, drilling over the sigmoid and transverse sinus, getting extra flap trajectory along the petrous bone, anterior petrosal, posterior petrosal combined approaches, exactly how you put it for us together and really embolization not playing a role, monitoring is really important. And really, the important four D's of meningioma surgery that Al-Mefty has often emphasized is so important and has played such a major role in my practice of meningioma surgery is always to dedress the tumor, is the first D. Second D, and the order is so important, devascularize the tumor first. It would really make your job a lot easier. It's gonna make everything simpler because you don't have to sort of stop your surgery, every layer of tumor removal to achieve hemostasis. The planes of dissection along the cranial nerves are gonna remain clean because the surgical field is clean since the tumor has been devascularized early on. And most important in these long skull-based cases, it is so critical to be efficient because if a tired surgeon reaches the last hours of surgery, and you have already spent yourself for so many hours coagulating the tumor, really gonna be very tired to manage the most critical part of the operation, which is dissecting the capsule from the surrounding sub-vascular structures. Obviously then proceed with debulking and then dissect the mass and respect the arachnoid membranes. I think the biggest friend of neurosurgeons in neurosurgery is the arachnoid membranes. And if we can protect those and leave those alone and handle them well, the cranial nerves and the vessels that are encased are also well-protected. So we prepared just like you mentioned, Bill for a combined approach or potentially a higher petrosal approach, as you can see this patient's placed in a lateral position, monitoring somatosensory evoked potential, motor evoked potentials in this case, and we went ahead and tried to do, what are your thoughts in terms of just using the retrosigmoid approach, cutting the tentorium and see how much we can resect? If we feel that approach wasn't enough, we could always extend our incision further and use the medial fossa to proceed with the petrosectomy. Any thoughts to this point, Bill?

- Yeah, I think that's very rational way to approach this. It depends on the consistency of the tumor, how easy it is to remove because if you open the tentorium, you hope that the tumor is relatively soft and dissectable, so you'll be able to mobilize the superior portion down. But I think it's very reasonable to try from one approach to start and see if you can remove it and then extend it if you need to. And you've got the flap plan here to be able to do that.

- Thank you. Let's go ahead to the surgical video and see what we found in surgery. This is a left sided retromastoid approach. We'll make the video bigger for the viewers. And you can see the petrous bone that is very hypervascular here, right there, and really tentorium right up there and the junction of the tentorium and petrous bone. This is the superior petrosal sinus or brain that was coagulated and cut. And as you can see, the posterior fossa approach really gave us a very nice exposure of the base of the tumor along the tentorium. And we spent a good portion of the first hours really devascularizing this tumor. And it was really very bloody. And as you can see here, especially at the junction of the tentorium and petrous bone, we ran into some major bleeding. However, again, just spending that extra time getting these bleeding points stopped early on really pays off significantly later. And here's the seventh and eighth cranial nerve just between my puller is visible. And here as you can see the handling of the fifth nerve, the tumor is pushed away. You grab the arachnoid and then with using the arachnoid, you push the nerve away using very fine forceps. There's absolutely no manipulation of the nerve. There's no suction. There is no dissector handling the nerve and the nerve hopefully remains intact. Here he's really cutting the tumor along they tentorium, and you can see the edge of the fourth nerve entering the dura. And as you can see, you have to be very careful not to cut the nerve as you're cutting across the base of this tumor. You can see a very bloodless field and how you can appreciate the membranes. Here he is moving a little bit more medially and pulling on the arachnoid membranes to mobilize the mass away from the brainstem as you can see here. And again, this is the top of the tentorium to orient our viewers. Here is the edge of the tentorium. The fourth nerve anatomically is preserved, however, you can see some manipulation of it was necessary in order to make sure it's dissected off of the tumor. This is obviously the brainstem and midbrain and then the tumor is being pushed inferiorly after coagulated from the tentorium. Here he is cutting last attachment, any thoughts there, Bill?

- Yeah, I mean, I'd like to emphasize that meningioma surgery is really a surgery of the arachnoid membranes and identifying the key arachnoid membranes that need to be cut and dissected, but it's maintenance of those arachnoid planes and dissection of the arachnoid that makes all the difference. Here you're peeling the tumor off of the brainstem and I just wanted to emphasize that Ted Kurzy taught me long ago that you have patience and you take time and you work at it slowly and the pulsations of the brain over time help you with the dissection of an acoustic tumor or a meningioma in this case off of the brainstem and you can slowly work it off over time.

- Thank you, Bill. And you can see the attachment to the brainstem especially at this region, which was significant. The pia has remained intact, however, in that region, it was very attached and as you mentioned that patience is important. Here is that sort of exotic part of this operation. This is the midline where the straight sinus is. This is the edge of the tentorium, Bill and here he is cutting across to dura, just lateral to the straight sinus. This is the petrous tentorial junction right here. And we're trying to cut the tentorium along the base of the tumor and bring the tumor downstairs into the posterior fossa. Obviously, you have to make sure that the fourth nerve is protected along the edge of the tentorium, and it is not in harm's way of your micro scissors.

- Often the dura, as you know, is very vascular around the edge of the tumor here and needs to be cauterized quite extensively prior to cutting it. The important thing here as well is also looking for where the Vein of Labbe is dumping into the transverse sigmoid junction. And we have to make sure that we don't interrupt the Vein of Labbe as it joins the sinus system.

- I think that's an excellent point. That's a very unforgiving vein and here, when you're cutting across here, you have to peek under the dura as I am doing. And there is occasional breach in vein to the occipital lobe that you can coagulate and cut. This is the edge of the petrous bone, and you can see the tumor has been delivered downstairs into the posterior fossa, and we're coagulating the edge across the petrous ridge and the tumor is being removed, the portion that was present in the supratentorial space. Obviously, you wanna make sure the fourth nerve is not injured at this juncture of the procedure. And here is really the tumor and specifically supratentorial portion that's being removed.

- Beautiful job, Aaron.

- Thank you, Bill. This patient did well after surgery. Surprisingly, did not have any double vision and I don't think it was necessarily my technique. It was that probably the fourth nerve was already attenuated. However, its preservation I think is important. As you can see, the tumor has undergone reasonable resection. There is a small piece of tumor left along the petrous ridge which is that blind spot along the petrous bone. Even if you drill the petrous ridge as Sammy, Magic Sammy talks about the transmittal approach, it can be difficult to see around it. This piece of tumor grew just a little bit in about a year afterwards and when we do surgery and in the final follow-up has remained stable and this patient should return to work six months after her original surgery. So it was a satisfying operation and I really think it shows that sometimes using the basic approaches and being sort of more flexible with using the corridors intradurally will most likely offer at least some options in terms of minimizing the large skull-based exposures necessary for resection of these challenging lesions. Any other thoughts, Bill?

- No, I think that's a good demonstration of how you can extend the retrosigmoid approach and the opening of the tentorium gives you the corridor that you need to be able to remove the tumor in the supratentorial space. So I think I congratulate you on a job well done.

- Thank you, Bill. And I wanna thank you at the end of these two sessions for really the mastery of your techniques and really the amazing complex cases that you presented that are not only learning experience for many of our viewers, including myself. Thank you again.

- Thank you, Aaron, it's been an honor.

- Thank you.

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