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Mastering the Temporal Bone: Transpetrosal Approaches to the Skull Base and Vascular Lesions

Jim K. Liu

November 16, 2020

Transcript

- Hello, ladies and gentlemen, and thank you for joining us for another session of the Virtual Operating Room from The Neurosurgical Atlas. Our guest this afternoon is Dr. James Liu. Jim Liu from Rutgers Neurosurgery. Jim has been a great colleague. I have followed his career very closely since his finished his residency and fellowship. His commitment and dedication to technical excellence is truly exemplary. He is a master surgeon who has tackled some of the most difficult problems in neuro surgery, and today he's going to talk to us about one of the most difficult locations in the skull base and transpetrous approaches to the areas of the skull base. So, Jim, it's an honor to have you, very much looking forward to learning from you and let's please go ahead. Thank you.

- Great. Thank you, Aaron. It's certainly an honor to be here today and to speak in this platform for the Neurosurgical Atlas. Thank you for this opportunity. Let me go ahead and just get started here. So what I often tell my residents is you should have a chance to go see Michelangelo's David in Florence and if you see the David statue, it's a work of art, a true masterpiece, but what's more interesting is if you walk the hallways that lead to the David statue, you'll see a bunch of Michelangelo's unfinished works. And what you see here are these creations that are inside these pieces of rock. And some would argue that these are actually finished works rather than unfinished. But the idea is that when we drill the temporal bone as skull-based surgeons, we really have to envision these critical structures in the bone as if we have x-ray vision, as Professor Rhoton taught us. And we can see these neurovascular critical structures in the bone as we excavate them out when we drill the temporal bone. And so we must be like a Michelangelo or like archeologists, such as this magnificent wonder here of Petra. And so we must be like that when we're excavating the critical structures out of the temporal bone to get to our desired targets. When we talk about transpetrous approaches, I like to divide the clivus into fourths, into several zones. And I adapted this from our colleagues, Jacques Morcos. And if you look at the upper fourth, this can be primarily reached through an FTOZ or subtemporal. And as we get to the second fourth between the fifth and the seventh nerve, the anterior petrosal or the Kawase's approach really gets us to this region very nicely. And as we get lower on the temporal bone, adding a posterior petrosal variant can get us there nicely. And then of course, the lower fourth below the jugular foramen a far lateral transcondylar approach gets us there nicely. And let's not forget the retrosigmoid approach, which is a workhorse of a posterior fossa approaches. Gets used from the tentorium down to the jugular foramen. And of course, if you come medially, there's the endonasal transpetrous transclival approaches as well. So all of these approaches are nice to have in your armamentarium. Oftentimes we tend to hear from other surgeons that the transpetrosal will approaches are outdated, or you don't need them anymore. That I can do everything through a retrosigmoid approach. And while that may be true in a lot of surgical cases, I want to propose to you today that the transpetrous approaches are still very valid and very useful for a lot of variety of vascular and neoplastic lesions when indicated. The way we break it down is there's the anterior petrosal approach which is coming from a middle fossa perspective. Coming from a middle fossa through the tentorium, into the posterior fossa. While the posterior petrosal approach is mainly a pre-sigmoid approach coming behind the ear in front of the sigmoid sinus where you cut the tentorium and you get both superior and infratentorial exposures. So here's a diagram. An anatomical dissection demonstrating the approach you get to the brainstem between the fifth and the seventh nerves. And so you get this zone of access to the brainstem through an anterior petrosal approach. Some of the lesions that you can access through an anterior petrosal approach are petrous apex lesions, such as cholesterol granulomas, chordomas, chondrosarcomas and some upper petroclival meningiomas. Brainstem, you can access anterolateral pontine cavernomas, and as well as upper to mid-basilar aneurysms. What's nice about this approach is that it allows you the shortest distance to Meckel's cave. So when you open up the fibrous ring of the porous trigeminus here, you get access to this region of Meckel's cave, and you can move the gasserian ganglion anterior or posterior to get access to tumors that can creep into this space. One of the major advantages is you get this look-back view onto the brainstem. So take, for example, this recurrent epidermoid here, that's socked into the brainstem. This was initially treated through a retrosigmoid approach, and you can see that I had left some tumor hidden behind the cerebellum here because the retrosigmoid you have a blind spot when the tumor is socked in to the brainstem in this region. So it's hard to see behind this corner of the cerebellum, but the Kawase's approach gives you this look-back approach from an anterior to posterior direction so you can better access this area. You can also combine these approaches with either an orbitozygomatic or a posterior petrosal approach. So I tend to use the anterior petrosal as sort of a building block when combined with other types of surgical approaches. So in terms of head positioning, these are some useful nuances. I think we tend to position the head in a lateral position, but if you think about it, when the surgeon looks down at the petrous face and the head is in the lateral position, the petrous apex is really far from the surgeon. However, if you tilt the head about 30 degrees from horizontal, we'll see that the slope of the petrous bone is more flat so that when the surgeon is looking down to drill the petrous apex, the petrous apex target is actually closer to the surgeon, making it more ergonomically easier to achieve. Another nuance that you can use is the dropdown zygomatic osteotomy that you see depicted here. This allows the temporalis muscle to get more inferior so there's less temporal lobe retraction. In general, when we do the Kawase's approach, I tend to favor a larger skin incision because it gives you a wider craniotomy and doing a wider craniotomy at the temporal bone gives you more angles of freedom. So you're not working in such a narrow corridor. We do an interfacial incision here to protect the frontalis branch of the facial nerve. And then you can do this dropdown zygomatic osteotomy as an option. I will say that I rarely had to use this in most cases, but this is a useful adjunct to use. If you need to get more inferotemporal fossa exposure. This is an anatomical diagram we published some time ago showing the exposure of the petrous ICA with and without a transzygomatic osteotomy. And you could see that after the osteotomy, you get a much lower exposure, a wider working corridor to the petrous ICA. Here again, shows the diagram showing how the zygomatic osteotomy minimizes temporal lobe retraction so that you can come down lower to the target. So after you exposed this, the next step is to elevate the dura propia in an extradural fashion. And in terms of navigating the temporal bone, you must understand the middle fossa rhomboid that was described by Taka Fukushima. And once you understand the rhomboid structure and how you can navigate the middle fossa through this, you'll understand the Kawase's approach. So the middle fossa rhomboid is bordered by the back of V3 anteriorly, GSPN laterally and from GSPN to the geniculate ganglion here, and then the arcuate eminence posteriorly, and then the medial petrous ridge medially. And once you identify this rhomboid, you can drop a diagonal from the angle of the GSPN and arcuate eminence. And this relatively identifies the location roughly of where the IAC dura will be. And just anterior medial to this area is the cochlear. This area is often called the cochlear angle, and this is the region where the cochlea will be so that when you're drilling, you'll leave a roughly five millimeters of bone here to protect hearing as you're drilling. Remember the petrous ICA horizontal segment will be relatively parallel to the GSPN here laterally. So be careful of this as a roughly 25 to 30% can have bony dehiscence in the floor of the middle fossa. So here's a anatomical cadaver dissection showing the floor of the middle fossa. You should peel the middle fossa from a posterior to anterior fashion because this allows the periosteum to stay right on the GSPN, as you're peeling it down, and then keeping it towards the floor. You must divide the middle meningeal artery by coagulating and dividing it so that you can start the peeling. And you peel the dura propria off of the lateral wall, the cavernous sinus, between the two layers of dura between the dura propria and the periosteal layer of dura to expose V3 and V2. And so you get this nice view of the middle fossa rhomboid. Lateral to this is Glasscock's triangle. This is where the region of the horizontal petrous ICA will be. And of course, as we bisect that angle and identify where the cochlear is, this gives us an idea of where the danger zones will be, so that we can begin the drilling. Again, we should have an x-ray vision showing all the critical structures, the horizontal petrous ICA. Here's the vertical segment, the cochlear, the facial nerve, and then the vestibular structures of the semicircular canals. So once we've done the drilling, you must do it from a medial to lateral perspective. And of course, you can slowly uncover the fold of the IAC. And as you follow the IAC dura distally, remember that the nerve becomes more vulnerable as you go from medial to lateral. The nerve also comes closer to you and the diameter of the canal becomes more narrow distally. So you have to be careful as you're drilling out more distally, leave a little bone on the cochlear. And the inferior limit of drilling is generally the inferior petrosal sinus. And just lateral to this if you keep drilling, you can drill right into the clivus. So this is often useful for clival tumors, such as chondorsarcomas or chordomas. And here's the horizontal petrous ICA nicely exposed here. If you mobilize V3, you can see that you get additional exposure of the petrous apex, which allows more drilling. You can also unroof the foramen ovale and decompress the V3 to get more exposure by retracting it anteriorly to get this exposure. And of course, in some cases you can divide the GSPN and mobilize the ICA from the carotid canal to get the entire exposure of the petrous bone. And you may need to do this in some cases of chondroid-like like tumors. I've had several cases of chondorsarcomas, where this was very useful where the tumor eroded all this portion of the temporal bone. This is an article we published some time ago. Maximizing the exposure of the petrous ICA using this exposure. Published with Dr. Couldwell and Dr. Fukushima. And this was used largely to try to understand how we can better expose the petrous ICA to do petrous to supraclinoid bypass. Although this is a traditional bypass that we rarely do these days since a lot of these lesions, such as cavernous ICA aneurysms are now largely treated with flow diverters. So when we opened the dura, we open the dura at the temple base, and we incise the posterior faucet dura. And the key here is to ligate the superior petrosal sinus that you see here, and you can do this through just a simple bipolar, or you can use a suture or clips. But the key is to eliminate the venous bleeding and then start dividing it from either medial to lateral or lateral to medial, or even a combination of both. But the important thing is that when you divide the tentorium, you must visualize the entrance of the trochlear nerve. You must see the fourth nerve enter the tentorium and the cut needs to be behind the entrance of the tentorium. Be very careful of how much traction you put on the dural leaflets, because you can avulse the fourth nerve. It is very friable. So be very gentle with that. It is invested in a layer of arachnoid, so that layer of arachnoid can give you some protection as well. But once you've opened the dura, look how wide exposure you have to the brainstem. Specifically between the fifth nerve here and the seventh nerve here. But you also have great exposure between the fourth and fifth nerve and also above the fourth nerve as well. So you have different areas of the brainstem you can access nicely. Here's a cadaver dissection showing what it looks like here against the fifth nerve, and then the seventh and eighth nerve. And then here's a view showing the sixth nerve going into Dorello's canal and the Basal artery. So you can access all these areas using the Kawase's approach. So now that I've shown you some anatomical references and background, let's look over some cases. This is a 61 year old female who had headaches and ataxia from this upper petroclival meningioma. You can see it is a petroclival meningioma because by definition it should be medial to the fifth nerve. So here you could see the fifth nerve and here's the tumor situated medial to the fifth nerve going into Meckel's cave. So we'll do this through a frontal temporal incision, frontal temporal bone flap. Can we play the movie? So our first step is to divide and ligate the middle meningeal artery at the foramen spinosum. And we'll go ahead and divide it sharply. And then start the peeling procedure from a posterior to anterior fashion. Here, you can see GSPN coming into view. And so we'll peel from a posterior to anterior direction and then we'll start to elevate the dura propria off of the periosteal dura of V3. There's the foramen ovale. The adhesions of the dura can be adherent in this area. So sharp dissection with either scissors or a 15 blade feathering out. These adhesions helps release these dural attachments. And now we'll decompress the foramen ovale at V3 using a three diamond drill with a lot of copious irrigation. So by doing this, this will free up V3 and allow me to mobilize it anteriorly to drill off more petrous apex. Here is the middle fossa rhomboid identified. Here's the IAC in my view with the cochlear bone might be. So now we'll drill from a medial to lateral direction. And if we peel V3 anteriorly, we'll palpate the trigeminal depression, and then this allows us to drill the most anterior part of the petrous apex. So we do this using an egg shelling technique, identifying the IAC dura, and then we'll go ahead and open up the dura along the temple base. We'll go subtemporal and identify the supratentorial component of the tumor. Here's the tumor being de-bulked with an ultrasonic aspirator. And we'll de-bulk it down to the tentorial edge. Here, we're going to be careful to identify where the fourth nerve is and what you'll see is here's the fourth nerve coming into view. Here's the fourth nerve. So now we'll cut the tentorium here. We're starting from the medial edge, and now we'll come from the lateral side. Here's the superior petrosal sinus entered, and we'll just simply coagulate it with a bipolar. Sometimes I'll inject a little bit of SURGIFLO into the sinus to get it to stop, but you have to be careful not to inject too hard. You don't want the SURGIFLO to go into the transverse sinus. So now we'll open up the posterior fossa dura and finish the remainder of the tentorial cut and open up the arachnoid over the posterior fossa. Here, you're seeing the superior petrosal vein. This will be carefully divided right at its entrance into the tentorium. And now we're going to open up the fibrous ring of the porous trigeminus. What we're doing is we're following the course of the fifth nerve as it enters the porous trigeminus and you just cut the dura and this allows us to get into Meckel's cave. So here's the tumor that's in Meckel's cave, medial to the fifth nerve. And now we have this great exposure working right anterior to the brainstem, right in front of the fifth nerve. And so we're able to release and control the tumor that's in Meckel's cave. We'll simply deep off the tumor here and then collapse it in a extracapsular fashion, and then begin to peel it away from the arachnoid layer that's covering the brainstem. Here, I like to use some gentle tractions and gentle sweeping with the suction. And then here's the basil artery. Here's the brainstem, basil artery. And reconstruction is very important as well. We use a multilayered method with DuraGen followed by fat graft, followed by another piece of DuraGen. And then we'll swing a vascularized pericranial flap that was harvested at the beginning of the case. It's pedicled posteriorly here, and it's easy to swing in here to get a nice reconstruction. Next slide, please. So here's the pre-op and here's the post-op MRI. Complete removal and the patient was neurologically intact. Here's another case. This is a dumbbell schwannoma in a 38 year old male. You can see he presented with right-sided facial dysesthesia. Notice how the tumor goes into Meckel's cave. So for this approach, I also chose a Kawase's approach. This was done with a transzygomatic variant. So again, here we've elevated the dura propria extradurally to expose the middle fossa rhomboid. We'll go ahead and drill the middle fossa rhomboid, in an eggshell technique. You could see the cochlear bone has been preserved as is the arcuate eminence. So we'll go ahead and open the dura, divide the tentorium after dividing the superior petrosal sinus. Here's cutting of the fibrous ring of the porous trigeminus which will allow us access into Meckel's cave. You could see here's the fifth nerve, and now we'll begin to identify a plane of the tumor from the nerve. So we'll go ahead and de-bulk the tumor. And then here's the seventh and eighth nerves right here. This is the seventh and eighth nerves going into the IACA. That's the branch of AICA. And then you'll see the brainstem here. Here is the fifth nerve. This is the fifth nerve that's coming around, going into Meckel's cave. And so you must preserve as many fascicles as you can on the trigeminal nerve when you're dealing with these trigeminal schwannomas. So we preserving the main trunk of the tumor. We removed the tumor where it's arising from the fascicles. We can preserve the whole fifth nerve here, and there's the brainstem nicely decompressed. Here's the fifth nerve maintaining its integrity. Next slide, please. And here's the post-op scan. You could see complete removal. The patient had a mild residual facial numbness, which is typical, expected from these cases. Otherwise he's done very well with no other neurological deficits. This is a case of a 43 year old female who had this large skull base CP angle epidermoid tumor. You could see it extended all the way from the mesencephalon all the way down to the foramen magnum. So what I did initially was I did a combined retrosigmoid far lateral. Basically I took off the foramen magnum and I went and transcondylar. And you could see, I had a wide exposure along the length of the clivus and could remove the tumor as low as the lower cranial nerves. Here's nine and 10. Here's the seventh nerve. And then here's the fifth and the seventh nerve here in the bottom right corner. Let's play the video here. So sometimes there can be casualties here. You could see at the end of this surgery, I see a nerve that's floating and there is a cut end. Luckily, I find the other cut end, and I come to realize this is the sixth nerve. And it's very long since it's been stretched by the tumor. And I must've have avulsed it when delivering some of these fragments of the tumor. But if you recognize this, you must repair it at all costs because this is a nerve you can salvage. And so some people say, you can just glue the nerves together, but I prefer to suture it because suturing gives it a more secure repair. The two ends can be reattached with just one simple suture. This is a nine mill nylon stitch, and you just have to tie a few knots to get it to stay. And what I did was I rested the nerve on the petrous bone and put a little SURGICEL to hold it in place so it doesn't float around too much once you replenish the CSF in the cistern. Here's an endoscope view. You can see at the end, this is the sixth nerve here. Seven, here's nine and 10 at the bottom. And then here's the sixth nerve that's repaired with the suture anastomosis there. Next slide, please. So we got a decent tumor removal, but as you can see here, there was a blind spot. This was an area that I had difficulty seeing. I didn't want to retract the cerebellum. The facial nerve was very sensitive under tension. And even with an endoscope, I used an endoscope to look around this corner, but I didn't have great direct access. So I did have a residual tumor. Luckily at four months, her left sixth nerve palsy began to show some partial recovery. And then at seven months she had complete recovery of her facial nerve. Okay, next slide. Nevertheless, I continued to follow her and you can see at nine months post-op that residual started to grow and you could see there's a big mass now socked into this area right at the junction of the middle cerebral peduncle. So I knew that my previous approach couldn't get me there. So I had to come up with a different approach and I felt that coming in from a Kawase's would give you a better idea, a better view of this look back onto this area of the brainstem. So here is the middle fossa exposure of the Kawase's triangle. Here's the rhomboid structure. We go ahead and I extended this to drill off more of the upper mastoid so I can clearly see the superior semicircular canal. I skeletonized the entire otic capsule and the reason why I do this is this allows me to clearly identify where the superior canal is. So I can drill all of this temporal bone behind the otic capsule to maximize my Kawase's space into this area of the postmeatal triangle. So I go ahead and open up the dura in the middle fossa perspective, and then identify the fourth nerve. Here's the fourth nerve. And then you can see here's the fifth nerve and then the tumor extended towards the superior part of the cerebellum here. And then here's the view of the tumor being removed from the cerebellum. And then there's the little look back. Here's the look back view on the tumor that socked in to the brainstem. Here's the seventh and eighth nerves. This is the view that you cannot get from the retrosigmoid approach. And then once the tumor is removed, you can see seven and eight is nicely decompressed. And then here's the final view. You can see here's the basilar artery. Here's the sixth nerve that was injured that's been repaired. The seventh and eight nerves are intact and then looking more superiorly the fifth nerve and the fourth nerve here are all intact. So this is a great view of the post-op scan of what you can achieve through the Kawase's approach. Now, we can use Kawase's approach for some vascular lesions as well. This is a case of a mycotic aneurysm, dissecting aneurysm. The patient had presented with a superior cerebellar stroke, and you can see on the angiogram here, there's an abnormal finding coming off of the distal SCA. You can see their subarachnoids hemorrhage wrapped around the brainstem. The 3D angiogram showed that there was this dissecting fusiform aneurysm. It's important to recognize this because it doesn't look normal. It doesn't look like a regular saccular aneurysm, but it has this so-called Hiroshima mushroom cloud. So if you see this be aware of these lesions. This is most likely a dissecting aneurysm. Now, this area of the vessel is diseased. Now, if I had done this through a retrosigmoid approach, it would have been a deeper reach and getting proximal control of this proximal SCA would have been very difficult. So I decided to come through a Kawase's approach because this SCA along its longitudinal course would be nicely exposed in a longitudinal fashion where I have great proximal and distal control of the SCA coming from this lateral approach. Let's play the video here. So here we are drilling the petrous apex of the Kawase's approach. Here's the dura, the IAC. We'll open up the temporal dura and then cut the tentorium towards the free edge. There's the fourth nerve. And now we're opening up the arachnoid over the posterior fossa. And what you'll see here is the aneurysm will spontaneously rupture. So this is what you see in pseudoaneurysms. There's really no aneurysmal wall. It's just a smoking hole in the artery. And so I try to see if coagulation might slow down some bleeding. Obviously that's not working. So I applied one clip. Did not seem to work. So I applied a second clip and it's almost like a shot in the dark, but I kind of had an idea of where the artery was. And so now once we've gotten some control, we can open up the arachnoid and get a better idea of the anatomy. So there's the proximal SCA now. I can see it in better view. So we'll apply a temporary clip there and go ahead and find the distal. And there's the distal SCA. So I'll put a temporary clip there. And then now I'll inspect where the hole is. You see, this is like a big hole in the artery here. It's almost as if a bomb had gone off. You could see the edges of the artery. And this was not repairable. This was a very diseased vessel. So at this point, I decided to just clip ligate this area. The patient already had a stroke in this region. So I didn't think it was going to be feasible here to do an anastomosis. Next slide. So luckily the patient ended up doing well. There was no residual aneurysm and she did not have any deficit from this. So we went on to treat her with IV antibiotics. But this example shows us how a Kawase's approach. It gives you the advantage of proximal distal control of the proximal segment of this SCA. Now, petrous apex cholesterol granulomas can be useful using this approach. This is a 35 year old male who had this very large lesion who presented with a mild facial weakness Brackmann two and progressive hearing loss on the left. I do these mostly through endonasal approaches, but I think in this case, I chose not to do an endonasal approach because if you look at the corridor through the endonasal perspective, you have the prepontine CSF cistern here, and the paraclival carotid here. So the window of access is quite narrow, whereas through a middle fossa approach, it's quite accessible. And so the technique we used was a technique I published as a fellow with Dr. Dellashaw using a cyst catheter that drains into the sphenoid sinus opening that's created between V1 and V2. Now, we took this a step further and added a mastoidectomy, which my neurotology colleague likes to do. And we can put the cyst catheter from the cyst into this sphenoid sinus, put a second catheter from the cyst into the mastoid cavity where it can drain through the middle ear as well. So you have dual exhaust drainage. Let's play the video here. So what we're going to do is we're going to elevate the temporal lobe dura extradurally, ligate the middle meningeal artery, and then divide it sharply. This will then allow us to continue the peeling procedure. Now, it's very important not to get a CSF leak because you don't want to put a cyst catheter draining into the nasal cavity when there's CSF leaking. So it's very important to keep the integrity of the dura. Here's the GSPN. And then here is the cholesterol granuloma cyst, and we'll eventually pop into the cyst here. So here's the cyst being entered. You could see the typical cyst contents of a cholesterol granuloma with these cholesterol crystals. We'll decompress the cyst contents. And what you'll see is reinflation of the posterior fossa dura. Here's posterior fossa dura that's re-expanded, and we can excise the lateral portion of the cyst wall, whereas the medial portion of the cyst wall is very adherent to the posterior fossa dura. So this area of the cyst wall is very difficult to resect. So we keep this part intact to prevent CSF leakage. We'll then go ahead and drill the hole between V1 and V2. This will get us into this sphenoid sinus and then here's the sphenoid sinus. We can then insert the ventricular catheter into the sphenoid sinus and the other end of the catheter into the cyst. And the cyst also draining into the mastoid cavity. Next slide. So here's the post-op scan. You can see this is the three month post-op scan. You could see complete decompression of the cyst wall. Complete decompression of the brainstem as well. And he's remained recurrence free now for roughly 10 years. So this has been an excellent result for this gentlemen. Complete a return of his hearing and facial nerve function. And here's the post-op scan, again. You can see pre-op, post-op. Here's an example of a petrous apex chondrosarcoma. This patient presented with a left sixth nerve palsy. And what you'll see is that this tumor extends all the way from the petrous apex. It's compressing the sixth nerve here with this component of tumor, and then extends as low as the upper cervical region and hypoglossal canal. So here's the hypoglossal canal. This goes into the upper part of the neck. So what approach would we do to access this? So I did this through a combination of approaches. This was a combined middle fossa petrosectomy with a far lateral to get down into the upper cervical and hypoglossal region. So here, the neck is exposed. Here, you could see the tumor at the level of C1 right here. And then here you could see this is the far lateral transcondylar approach where we've drilled off the hypoglossal canal. And then this is the middle fossa perspective where we elevate the middle fossa dura. Here's the middle fossa floor. And as we drill the middle fossa floor, you could see there's tumor that's in the floor of the middle fossa. And then at the end, what you see here is this is the sigmoid sinus. Here's the sigmoid sinus. And then this is the hypoglossal canal that's been skeletonized. And so we're sticking in a probe through the defect where the tumor was, and this probe can be viewed from above where... Here's the petrous ICA. And you can see the probe here being viewed from the middle fossa perspective. So this tumor had eroded through the temporal bone all the way down to the hypoglossal canal that you saw in the MRI scan. And then here's the post-op scan. You could see a near total removal of the tumor here pre-op and post-op, and the patient did quite well. Normal facial nerve function, neurologically intact, and her sixth nerve palsy pre-op returned immediately after decompressing the tumor post-op. So let's transition to posterior petrosal approaches. We mentioned this is a pre sigmoid perspective. It's done through a L-shaped craniotomy and combined with a mastoidectomy. Now, I often combine this with an anterior petrosectomy, much like the way Professor Al-Mefty has described it with his diagram here, by keeping the otic capsule intact, and then drilling the anterior petrosectomy with a retrolabyrinthine posterior petrosectomy. Especially if the hearing is intact, this gives you multi-angled approach to the skull base, as well as access to the posterior cavernous sinus and Meckel's cave. So here's an example of a recurrent brainstem cavernoma. This patient had a prior retrosigmoid approach. Had one attempt to resect it done at another hospital. It recurred, and then the patient underwent an endonasal transclival approach, also at an outside hospital to resect the recurrence. And several years later, the patient re-hemorrhaged represented with more deficits with this recurrent brainstem cavernoma. So you can see he's got a baseline facial palsy, baseline sixth nerve and hearing dysfunction. So I felt that the best approach to get to this was an anterior transperosal and because it extend down low by the medulla I combined it with a posterior petrosal. Notice that there was a large DVA going right into the middle of the brainstem. So you must preserve this. If you injure this you can get a venous infarct. So we did this through a combined petrosal approach. This is the incision that the patient previously had and I went ahead and just extended it anteriorly to get the combined petrosal exposure. We raised a large pedicle pericranial flap in the beginning, and I don't do a L-shaped craniotomy, but instead I just do a wide temporal craniotomy. And then I just do an extended mastoidectomy where I include the retrosigmoid exposure with the mastoidectomy. Let's go to the video. So here's the middle fossa exposure. We're elevating the temporal dura. And there's the GSPN. We're peeling it from a posterior to anterior fashion. We ligate the middle meningeal artery and then divide it sharply. We'll then start the peeling. And a little bit of venous bleeding is encountered from the posterior cavernous sinus. You can control this with a little SURGIFLO packing. We'll go ahead and drill the petrous apex Kawase's triangle using a diamond drill. And then we'll combine it with a mastoidectomy here. Here we're drilling the mastoid, finding the mastoid antrum and finding the lateral semicircular canal. This will then allow us to skeletonize the other semicircular canals to identify the otic capsule. Here's the lateral canal, posterior canal, and superior canal. And then we can hug the otic capsule drilling right next to it to maximize our pre-sigmoid parapetrosal dural exposure. And then we'll finish off the anterior petrosectomy. And then go ahead and open the dura by incising down low at the base of the middle fossa. And then we'll elevate the free edge of the tentorium. And we'll cut the dura towards the superior petrosal sinus. Open up the posterior fossa dura. And then ligate the superior petrosal sinus. Here, we're using a bipolar and then dividing it sharply. Now, there's the fourth nerve. You must identify the fourth nerve as we're cutting the free edge of the tentorium, staying behind the fourth nerve. There's the fifth nerve and opening the arachnoid over the brainstem. You can see the brainstem has a hemosiderin staining. Now, there was a lot of scar tissue here in the presigmoid dura, and a lot of bleeding encountered. So I decided to just work primarily through the Kawase's corridor. And it turned out that I could do everything through the Kawase's corridor here. So here's the cavernoma. It had an exophytic component that presented itself just below the fifth nerve. So now, we're working dissecting around the cavernoma. Putting a little gentle traction with one hand and suction dissection with the other hand using a six inch Fukushima suction. And so we can remove this through a piecemeal fashion with a little gentle traction, suction dissection. And we use the image guidance. I know that there's more cavernoma in the intrinsic part of the brainstem. So we'll go ahead and make a small cortisectomy and we identify more cavernoma. Sometimes in these recurrent cases, you can have some seeding. So it's kind of seeded in several places. So we're able to identify the cavernoma that's just medial to the fifth nerve. We'll combine our two corridors here in the brainstem, following the hemosiderin stain. Then there's the rest of the cavernoma. There was a lot of adhesions in this case, since this was a recurrent case with previous surgery. So I ended up using a lot of sharp dissection. Here we're using a disc dissector to dissect the rest of the cavernoma from the brainstem. And since there's a lot of scar tissue, I ended up using a lot of microscissors cutting. Cut through some fibrous tissue that was in the brainstem to remove portions of this cavernoma. There's the DVA. We confirmed that with image guidance. So we'll also use an endoscope. I often use an endoscope in open transcranial approaches as well to look around corners. There's the fifth nerve, and then there's the DVA. There's the fourth nerve preserved. And then multi-layer reconstruction. Here, you have to seal off the entrance to the middle ear. I used a little bone wax followed by some hydroxyapatite cement, a fascial lata sling, and then a little bit of fiber and glue followed by fat graft and then a pericranial flap here to prevent any CSF leakage. Next slide. This is a post-op CT temporal bone that shows you the different avenues of access through the anterior petrosal and posterior petrosal. Different windows of access. And then here's the post-op MRI scan showing complete removal of the cavernoma. This patient regained his sixth nerve, seventh nerve and hearing function back, and his weakness on the right side improved to about four out of five. And he's now a motivational speaker who recently wrote an autobiography. Here's an example of a petroclival meningioma. You could see it extends into Meckel's cave. Severe compression of the brainstem. This patient was severely ataxic. It's got some supra and infratentorial components. So I felt this was best approached through a combined petrosal approach. Large C-shaped incision with elevation of a pericranial flap for reconstruction. This is the example of a temporal craniotomy combined with an extended retrosig mastoidectomy. Let's go ahead and play the video. So here we're doing the retrolabyrinthnie petrosectomy combined with a retrosigmoid exposure. You must decompress the bone behind the sigmoidsinus, which will allow you to mobilize that sigmoid sinus posteriorly, to give you that window of access in the presigmoid space. Since we've done an anterior petrosectomy as well, we have great access to Meckel's cave. So here in this case, we're ligating the superior petrosal sinus with a suture, and then cutting the tentorium. Here, we've exposed the tumor underneath the tentorium. Here's the seventh and eighth nerves right there. And then we're gonna start de-bulking the tumor and then peeling the tumor away from the brainstem. Luckily here, the tumor was soft and suckable. And we're now cutting the tentorium towards the petrous apex. And then here's the fifth nerve. You could see the fifth nerve going into the porous trigeminus. We'll continue to de-bulk the tumor with an ultrasonic aspirator, and then using sharp dissection to dissect the tumor off of the rest of the tentorium. You could see the tumor is stuck to the tentorium here. And then here's the fifth nerve. We can use sharp dissection to dissect the tumor off of the fifth nerve using a combination of ultrasonic aspiration, and then sharp dissection with micro scissors to detach the adhesions. Here's the last component of the tumor being dissected. And now we'll take an endoscope and look at the resection cavity. You can see there's a larger section cavity here, and we'll use this technique of fascial sling technique. We'll suture a fascial sling, which will act like a hammock to hold the fat graft. And then this holds the fat graft in place. And then we can rotate the pericranial flap over it. Next slide. Here's the publication we initially described using this technique for presigmoid dural defects. You can attach the fascia in several places with interrupted sutures, and then you put the fat graft on top to prevent the fat graft from herniating into the defect. And we find this technique to be quite effective in preventing CSF leaks. We then bolster the fat graft with a Medpor tightened plate. It really holds the fat in place and applies pressure to prevent a leakage of CSF. And again, you can see the variable windows of access through an anterior petrosal and posterior petrosal using this combined petrosal approach. Here's the pre-op scan. Here's the immediate post-op scan. And then here's the delayed three months post-op scan. And you can see she's done quite well. Neurologically intact, got her gait function back. Here's an example of another large trigeminal schwannoma. This patient presented with severe gait ataxia and facial numbness. You can see this pattern of enhancement. Typical of some cystic trigeminal schwannomas. Let's play the video here. This one, I chose a combined petrosal approach. You can see we've already drilled out the otic capsule here and the petrous apex. So we'll go ahead and open the dura. This is a presigmoid dural incision, coagulation of the superior petrosal sinus, and then cutting the tentorium. We'll incise the tentorium towards the free edge. Here's the arachnoid dissection. We'll open up the CSF cisterns to allow brain relaxation. Now we can start to work around the tumor. Here we've identified the trigeminal nerve cisternal segment. We'll stimulate it just to make sure it's not the facial nerve, but rather the trigeminal nerve. So we'll de-bulk the tumor initially. And after some initial de-bulking, we can start to peel the tumor away from the brainstem. Here, you can see the brainstem coming into view, and now you can start to see the facial nerve and the eighth nerve coming to view on the inferior aspect of the tumor here. You can see there's the seventh and eighth nerve complex, and then we'll use a microban forceps. This is one of my favorite instruments to use to dissect by spreading and peeling the tumor from the brainstem. Here, we're de-bulking the tumor and then cutting the rest of the tentorium into Meckel's cave. So now we'll look more superiorly. Here we'll see the SCA vessel and there's the fourth nerve coming into view. So now we'll open up the porous trigeminus to get into Meckel's cave. Here's tumor that's in Meckel's cave. We can now suction the rest of the tumor here in Meckel's cave, working above and below the fifth nerve. We try to keep the fifth nerve intact and remove the least amount of fascicles only where the tumors is detached preserving the main trunk. And so here's the last components of the tumor that we're able to start peeling away from the brainstem. There's the brainstem and branches of the basil artery. Here's the tumor being removed. And then there's the basil artery. There's the sixth nerve. There was a small remnant of tumor I left attached to the sixth nerve. I didn't want to injure it, but overall, a near total removal. Basil artery, sixth nerve, seventh and eight nerves all intact. Using an endoscope to look around corners and the closure here, we're using the fascial sling technique. Putting a hydroset cement over the entrance to the middle ear, and then using a fat graft, dural substitute, and pericranial graft. And then a Medpor tightened implant. Next slide. Here's the pre-op and post-op scan. Near total removal. And the patient was neurologically intact with a little bit of mild facial numbness. Now, vascular lesions. This is an interesting case. This was a very deep petrosals AVM. It was on the petrosal surface, but at the deepest point lodged right where the brainstem meets the cerebellum. I could have done this through a retrosigmoid approach, but I felt better doing this through a combined petrosal only because I felt I had better control of the SCA vessel here. And you can see this is the SCA vessel. Here's the AVM. You can see it's a very small micro AVM coming off of the SCA. And I like to put the 3D angio into perspective of the surgical view and in order for me to predict what it will look like. Let's go ahead and play the video. So here's the pericranial flap, and we've done the petrosectomy here. Here's the otic capsule. Here's the otic capsule. Anterior and posterior petrosectomy have been performed. We'll then open up the dura. Open up the arachnoid over the cerebellum. This is the cerebellum here, the most anterior part of it. Here's the brainstem. And so here's the SCA vessel. Here's the SCA vessel. And you could see the cerebellum here has a little hemosiderin staining. So we'll do a little cortisectomy in this area. And notice when we coagulate this vessel, notice how this arterialisation of this vein now becomes blue with time. So there was some fistulization into that draining vein. This gives us a clue where the AVM is. So we'll continue to explore this area and we can start to see an anitis forming. This is a small micro AVM. There's some AVM vessels here. We'll continue to work around this circumferentially and slowly de-vascularize this AVM. Dissecting it from the surrounding white matter using a combination of bipolar cautery and sharp dissection. You can see at the end, this is a charred AVM. That's removed. There's the resection bed. Next slide please. So here's the final removal. No residual AVM on the post-op angio and patient was neurologically intact. So when we talk about posterior petrosectomy approaches understand that there's different levels of petrosectomy that you can do tailored based on the hearing function. You can do a transcrusal or a partial labyrinthectomy where the superior and posterior canal are removed and theoretically preserve hearing. If the hearing is gone, you can do a translab. And of course, if you transpose the facial nerve, that would be a transcochlear approach. However, we've largely abandoned this only because you almost always get a facial nerve palsy that only recovers to a Brackmann three. And in some cases, which I'll show you in a moment, you can do a total petrosectomy. So this is from one of Dellashaw's articles, and I've rotated in a way where it would surgically make sense. This is the retrolab exposure to the petroclival region. And as we sequentially remove the bone here's the transcrusal approach. You get more exposure to the petroclival region. This is a translab. And then if you mobilize the facial nerve, this is the transcochlear variation of it. So you get the maximum exposure with transcochlear. This is a Rhoton's dissection showing the same degrees of petrosectomy. This is the retrolab. And then if you remove the superior and posterior, this is the transcrusal variation. Here's the transcrusal variation. And then here's the translab and then the facial nerve completely skeletonized. So you'll see, in a moment, when the facial nerve is now transposed you have access to the cochlear that you see here to do the transcochlear approach. And then this will give you the maximal petrosectomy that's needed to access the petroclival region. So when you're doing the transcrusal, how do you technically save hearing? Well, as you're drilling you need to pack off the membrane in this canal using bone wax. You should use a lot of irrigation with a suction irrigator to flood the field. And so this is the pre and post exposure to the petroclival region using this transcrusal approach. Here's an example where I used that approach. This was a large petroclival meningioma extending into Meckel's cave. You could see how much degree of brainstem compression there is and if I had done this through a retrosigmoid approach, this would require a lot of cerebellar retraction. So instead I felt this would be better approached through combined petrosal with a transcrusal variant. And I was able to keep the hearing and facial nerve function intact using this approach with a near radical removal here, as you can see. This is an example of a patient with an infratemporal fossa meningioma who was operated on by another surgeon in 2007. They had left some tumor adherent to the petrous ICA. It was radiated and now was recurring. And so you could see the tumor has recurred here, and it was now invading the facial nerve, the jugular bulb, and the petrous ICA. She presented to me with a complete facial nerve palsy Brackmann six. So I decided to do an aggressive approach to this. This was an extended transjugular approach with facial nerve grafting. This was essentially a total petrosectomy. We did a balloon test occlusion, which she passed. So I chose not to do a high flow bypass, but you could see here, the tumor is here and it's encased the ICA here. And so I just went ahead through this middle fossa approach. You could see here's V3, here's the petrous ICA. We'll go ahead and clip and excise this portion of the tumor that was encasing the ICA. And then here is the resection of the jugular bulb. This is very similar to resecting a glomus tumor. You tie off the internal jugular vein and pack off the sigmoidsinus, and then you can open up the jugular bulb and then resect the tumor that was here in the jugular bulb. And so here's the final picture of the tumor removal. Here's the entire infratemporal fossa exposed. Here's the sixth nerve that's kept intact. And then we find the two ends of the facial nerve. This is the facial nerve in the distal fallopian canal. Here is the proximal end of the nerve. And we'll use a sural nerve graft here to graph the two ends of the facial nerve with the nine mill nylon sutures. And then we'll reconstruct the skull base using this Medpor tightened implant. Here you could see, this is a total petrosectomy. The entire temporal bone has been resected. And then here's the pre-op, here's the post-op scan. You can see complete removal of this invasive meningioma, and you can see the progression of her facial nerve function. This was her pre-op with a Brackmann six, and then here she is at a one year and one and a half years. You can see she's had significant return of function with the facial nerve grafting. So that's a very useful technique to use. Always try to repair the facial nerve if you can using an interpositional graft. You can also use a 5-7 transfer. If you work with a good facial plastic surgeon, that's a very useful technique as well. So lastly, I just want to talk about how you can use temporal bone approaches for jugular foramen tumors. This is an article we published some years ago, showing the technique for infratemporal fossa approach to the transjugular region. This is basically a infralab mastoidectomy with a high cervical neck exposure. Here's the hypoglossal canal being exposed. And then as you resect the tumor in the jugular bulb, you must preserve the medial wall of the pars nervosa right here to preserve the lower cranial nerve function. And then you can go intradural with this exposure as well. Here's Al-Mefty's diagram showing an example of a glomus jugular tumor and how you should preserve that medial wall of the pars nervosa to maximize preservation of lower cranial nerve function. So here's an example of a 51 year old male. He was wasting away because he couldn't eat with a mass in the back of his mouth. He has tongue atrophy and a winged scapula. These are all nine through 12 palsies due to this jugular foramen chordoma. This chordoma was quite large and invasive invading into the perapharyngeal space and intradural space. You could see the occipital condyle and clivus has been eroded so he had some neck instability as well. So we did this through a lateral transcondylar approach. Transjugular approach. Let's play the video. So here we're skeletonizing the fallopian canal and the sigmoid sinus. Here, you could see the tumor as it completely eroded the occipital condyle. We're removing the tumor from the occipital condyle. And now we're skeletonizing the V3 segment of the vertebral artery. Here's the vertebral artery. And now we're doing a fallopian bridge technique. This is the fallopian bridge. This is the facial nerve. And we're working in front and behind the facial nerve. We'll tie off the internal jugular vein, and then open up the sigmoid sinus and occlude the proximal sigmoid sinus intraluminally with gel foam. We can then inject SURGIFLO distally to occlude any back bleeding from the inferior petrosal sinus and then resect the lateral wall, the jugular bulb. This'll give us access to this chordoma that's in the jugular bulb. And then we'll turn our attention towards the parapharyngeal space. We've retracted the carotid arteries laterally to get access to this tumor in the neck. We can then de-bulk it with a series of tumor aspirators and then resect the tumor up to the jugular vein. And then we'll resect the remainder of the occipital condyle. You can see it's a loose piece of bone. It'll give us access to the cranium vertebral junction here. So now what you're seeing here is this is the clivus. We're now drilling the bottom of the clivus and then you'll see in a moment we'll be able to access the tip of the odontoid. So here's the tip of the odontoid here. We'll now drill off the tip of the odontoid to get more access to this tumor that's in that C1, 2 region. We'll then go intradural. Here's the vertebral artery. It's laterally. Here's the vertebral artery. And now the remainder of the tumors is in this portion in the clival dura. Here's the lower cranial nerves that are dysfunctional. We'll go ahead and divide them. And then we can resect that dura that's in the clivus and here's the VB junction. We have complete removal of the tumor, large dural defect. We repair it with an Alloderm. We'll SURGICEL and then we have to occlude the entrance of the middle ear with a little bit of bone wax, and then a fat graft compressed with a Medpor tighten. Next slide. So here's the pre-op scan. And here's the post-op scan. You can see complete removal and he had to undergo another stage for instability to stabilize the OC stability. And he pre-operatively had a PEG and TRACH. We did have to use a lumboperitoneal shunt. He did have a pseudomeningocele that was difficult to control. We treated it with an LP shunt that worked effectively. And the last case I'll show you here is this glomus jugulare tumor. You could see here, it has a sausage shape to it invading into the jugular foramen. Very hypervascular tumor. These tumors need to be embolized pre-operatively. And so we'll use this lateral transjugular approach. Here, we've tied off the external ear canal and get this exposure in front of the ear. We work with ENT on these approaches. And so we'll tie off the internal jugular vein here and open up the sigmoid sinus proximately, and intraluminally occlude the sigmoid sinus. We can then inject the SURGIFLO distally to occlude the back bleeding from the inferior petrosal sinus. We'll then open up the jugular bulb and then sequentially get hemostasis as we expose the tumor here in the jugular bulb. There's always a little bit of back bleeding here in the infrapetrosal sinus. And then resect the tumor here that's in the temporal bone. Here's some coils. You could see some coil mass from the embolization. And then here's the tumor down in the jugular bulb being dissected. We'll pack it off with a little bit of SURGICEL. And now we'll go ahead and open up the area where the cervical portion meets the jugular bulb. This area can be difficult to expose, but the key here is to find the rectus capitis lateralis muscle, and then resect that. And then you'll get exposure of the jugular foramen. We'll then open up the lumen of the jugular vein. And now you could see the inferior component of the tumor. It's got a sausage shape appearance. And so we can go ahead and resect these adhesions using sharp dissection. Here we'll open up the lumen of the jugular vein. And you can see there's the tumor that's occupying intraluminally. So now, we'll go ahead and elevate the tumor from the lumen of the jugular vein. And luckily this was not very vascular. It's already been largely devascularized from embolization and also inter-operatively. And so here's the last component of the tumor being removed. You can see a large sausage shaped paraganglioma and these are all the lower cranial nerves preserved. So we preserved the pars nervosa medially. Here's a little bit of fat graft followed by Medpor tightened implant. And there's the reconstruction. Next slide. Here's the post-op scan. You could see a complete removal here with a Brackmann one. The patient did need a temporary PEG that was removed at one month post-op, but overall an excellent result. So in conclusion, I still believe that transpetrosal approaches remain an important strategy to have in our armamentarium as skull-based and vascular neurosurgeons. Sometimes it can provide a more advantageous angle of attack to the brainstem and to your desired target. And one must master the temporal bone much like Michelangelo or an archeologist. So again, Aaron, thank you again for this opportunity and this time to share my thoughts on these approaches. Thank you.

- You're welcome. Spectacular work. Really a piece of art, what you do. And I'm really proud to have somebody like you as a colleague, Jim. Along the years, we have grown together we have gone through our careers along the same timelines and it's really fun watching you do your great surgical masterpiece. I think these are extremely difficult cases. Not something everyone can do. I have to be honest about that. And if I may ask one question, Jim, what do you think is the most important factor in these difficult cases for success? Besides knowing the anatomy, obviously, which is important, besides having the team, besides having the passion for technical excellence, which you do have. What do you think is the other most important ingredient?

- That's a tough question. I wish I can give you three answers to that. I think what's helped me over the years is constant rehearsal in the lab. And you know, I feel that neurosurgery is really all about lifelong learning. And even til today, I'm still learning. And I was doing a virtual cadaver course last week that was televised and I had the opportunity of drilling and dissecting in the lab. And even then I was still learning. I was learning a new dimension that I had not seen before or a little nuance that I can do to make myself better. So I think it's constant rehearsal, constant learning, and continuing to push yourself to climb that mountain.

- I think you couldn't have said it better. I think what I would say is the most important ingredient is self-reflection, self-learning. Self-reflection in terms of watching your own videos, other people's videos, learning from others, being honest with yourself, brutally honest. That every next case should be better than the last one, no matter how well the last one went. I think those are the most important factors. To be self-critical and not to get lost in our egos. I think those are the important factors. So again, Jim, I wanna sincerely thank you for spending the time, showing your incredible cases. And I look forward to having with us again in the near future.

- Great, thank you very much, Aaron. Appreciate this opportunity.

- You're welcome. Thank you.

- Okay.

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