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Grand Rounds-Minimally Invasive Transcranial Operative Corridors: Techniques

Dan Kelly

May 15, 2014


- So now let's shift gears and talk about the supraorbital eyebrow craniotomy. And this is a really nice approach for many lesions that are in the frontal fossa and the parasellar regions such as meningiomas, some craniopharyngiomas which are not retrochiasmal in location which extends laterally or extending anteriorly. And then we also use this approach now for many intra-axial frontal and some medial temporal lobe tumors. Now this approach has been around for a long time and its... I think it's used more and more because it really is sort of the sweet spot of the fronto-temporal craniotomy, the sweet spot of pterional craniotomy. The entry point is on the floor of the frontal fossa and it really gives you this wide exposure into the frontal fossa, the parasellar, and the perisylvian regions. And again, it requires very little dissection of the scalp and in most cases, as I'll show, has an excellent cosmetic result. Dr. Perneczky and his group and Dr. Reisch were really the ones who the champions of this approach. They have this large publication, a large series of over a thousand patients, they published in 2005 showing some of the technical nuances. It's really been around for a long time and it's shown here there've been numerous other publications over the years including in pediatrics, and I think it's really a nice approach. And it's akin to the endonasal endoscopic approach in that it's working through a small corridor. You have to be comfortable working in that small corridor. You need to have the refined instrumentation and in some ways, very, very similar to the endonasal endoscopic approach. This was a publication by Nikolai Hopf and his group showing its use in removing medial temporal lobe lesions. So you can do a very nice splitting of the Sylvian fissure and take out medial temporal lobe lesions quite effectively with this approach. We also had a recent publication using it for intra-axial tumors, mostly metastases and some gliomas. And so, I think it can be used for a whole variety of things, both intra-axial and extra-axial. So, the positioning is really very similar. For pericranial craniotomy, the patient's in pens. They had this on back. A little bit rotated about 30 degrees, malar eminence is prominent. The skin incision goes from just medial to the supraorbital nerve notch as shown here. Extends out in the eyebrow and to the termination of the eyebrow. And in some instance, you can take it a little further in a skinfold. Very important to raise a pericranial flap for cosmesis. I'll talk a little bit about where the Burr hole goes, how the craniotomy is done, issue of the frontal sinus, and then we'll talk about the closure. So, this is a case showing the exposure here. You can see the outline of the craniotomy here. You can see the supraorbital nerve here is preserved. The Burr hole typically goes just below the superior temporal line, and this provides you about one and a half to two centimeters in height and about 25 millimeters in width. Very generous space to work once you get used to working in these smaller spaces. Very important that the height is enough and this is why fish hooks are really important to bring the exposure of the supraorbital area so that you can get a wide enough, a tall enough craniotomy. Otherwise, you gonna have trouble getting your bipolars open, and that's obviously a big problem. If you can't use your bipolars, you shouldn't be using this approach. So once you open the bone, it's very important to drill down, to bevel the inner table here to give you this really flush approach into the frontal fossa. That is really critical. This is an older case. We don't typically use tack ups anymore, but you can if you like. But this drilling of the inner table is really critical to get as wide of an exposure as possible. So, here's a nice case which is appropriate, in my opinion, for a supraorbital approach. It's a meningioma involving the frontal fossa. Here you can see indenting of the frontal lobe. You could certainly do a bicoronal approach. You could do a pterional craniotomy, but you can really get to this through an eyebrow approach. And so here's just the exposure here. The fish hooks, you can see. You can see the exposure, the superior temporal line. These are fish hooks here. These are just sutures. You don't wanna pull too hard on the lower aspect of the incision 'cause it will pull the scalp down and limit your supraorbital exposure. Here you can see the Burr hole. And in this particular case, the patient had quite a big frontal sinus and you can always map that out on your preoperative MRI. If you feel you're gonna get into frontal sinus, we always prep for an abdominal background and we do not feel this is a major contraindication on the procedure. And all of the supraorbitals we've had, we've had one postoperative CSF leak. So, it can certainly happen, but you need to anticipate that this is gonna happen. And then again, bevel this interior bone edge here to give you maximum exposure. There's the supraorbital nerve again. Okay, so here, we're gonna show you this left supraorbital craniotomy. We've done the bony exposure here. We're just identifying the tumor and separating it away from the surrounding brain. With micro dissectors, we're starting to cauterize the base of the tumor to take away some of the blood supply. We don't typically need a retractor in these cases because you really come down on the floor of the frontal fossa. Very important to open up the cisterns and get some brain relaxation. Here you can see we're dissecting away the arachnoid and then starting to lift the tumor away from the brain, lifting it up. This is a two-person technique. Internally debulking it with an ultrasonic aspirator and then gradually debulking it just as you would with any meningioma and progressively lifting it away. In this case, the branches of the anterior cerebral were coursing by. Very important to be cognizant of those. We like to use the Doppler to identify them if there's a thin rim of tumor. Here you can see the last bit of tumor coming out, just separating it off that branch of the anterior cerebral there, and then achieving what appears to be a complete tumor removal and then taking a nice panoramic view with the microscope. In this particular case, this was an older case, we did not use the endoscope. The postoperative scan three months after surgery, no evidence of a recurrence or residual. It looks like a gross total tumor removal. Here's just showing you the closure. So, that was a very large entry into the frontal sinus. Here you can see it's filled with fat. We do not cranialize these and I would encourage you not to do that. Keep the opening as small as possible, fill it with fat, lay some collagen over that, and then the bone flap goes up against that to help prevent any seepage of fluid. You can see the titanium plates and screws here. And I'm gonna show you another video of the closure. And this is her three months after surgery looking good. Many of the patients will get a transient forehead palsy. They will have some creases here, but this almost always comes back. They often get a little bit of numbness from stretching of the supraorbital nerve as well. So, when you're closing, just a few key points, make sure you didn't get into the frontal sinus and not realizing that you shaved along it. We always use college sponge over a water-tight dural closure if you can. The bone flap is fixed with a lateral Burr hole cover and a medial straight plate, and I'm gonna show you an example of this. The pericranial cuff is important to bring over this. We don't use it for repairing the CSF leak. That's important for cosmesis. And I'll show you a video of the galeal closure, and then we generally put a gentle head wrap on for about 24 hours just so they don't get swelling or simply a hematoma. A quick video on the closure. Just irrigating here a water-tight dural closure if you can get it. It's always possible but if you can, it helps. And then once that is done, epidural hemostasis, obviously, we put a pretty good layer of collagen all around and make sure that it's really filling and covering all the dura. Now, here you can see we're maneuvering the bone flap into place and this can sometimes be one of the harder parts of the case. We stuck the one plate under the supraorbital nerve. And in general, you want the bone flap to go to the top of the exposure because you don't want a gap on the forehead. So, the gap will then be under the eyebrow and which is more cosmetically hidden because of the eyebrow. In this particular case, this was a young woman. We actually put some bone cement in here and this is a nice thing that you can do which fills in that gap and will prevent that sort of sunken look. And so, this is something you can do. And then finally, what you're gonna see is the pericranial cuff. So, they we're just irrigating, the nerve is intact, and here we're going to then bring that pericranial cuff back and that needs to be sutured to the correct layer to really optimize the cosmetic result. And this are just some examples of closures here. You generally get a very nice cosmetic result. So here's an olfactory Groove meningioma. This is a patient in whom you could potentially do an endonasal endoscopic approach. You could do a bifrontal craniotomy. There's many ways to do this, but you can also do an eyebrow approach. Supraorbital approach for this meningioma here. We've opened the cistern. We've let some CSF off. You can see we have some telfa on the frontal lobe. Again, no use of retractors. We're separating the posterior aspect of the tumor from the optic chiasm there. Now, you can start to see the left olfactory nerve. We're cauterizing the base of the tumor and just starting to mobilize some of the tumor here. Taking the blood supply along the base, I think, is critical for these tumors and helps you deal with bleeding. This was not a super vascular tumor, but this certainly helps. Once you started on the base there, we then always use the Doppler because in this particular case, the interest group of vessels are draped over the top of the tumor here. We've identified those coming in posteriorly and now we're starting to separate the tumor pseudocapsule from the arachnoid here. Then using sharp dissection, lifting it up gently and progressively manipulating the tumor. You can start to see the anterior cerebral there. And then, really lifting the tumor up away from the brain. And this is just showing arachnoid here. Arachnoid bands being cut back along the chiasm. Now, we're doing internal de-bulking. In the supraorbital approach, you can certainly get the ultrasonic aspirator in. This was a fairly gradient firm tumor and we were using the ultrasonic aspirator not frequently, as well as some larger scissors, tenotomy scissors in there, cutting the tumor away. Again, always important with meningiomas, keep the arachnoid with the patient. And gradually, after you've internally debulk the tumor, and now we're bringing the endoscope again. And you can see that with the endoscopic view, you can see where we cauterize the base. You can see the optic nerves here. We're looking at the right optic nerve there. We're using the ring curates to elevate some of this carpeting of tumor that goes down along the planum or the tuberculum there. You can see the one olfactory nerve which we were not able to preserve, but a gross total tumor removal accomplished. And just taking our telfa out. And I think you can see that the brain looks quite good without the use of the tractors.

- Dan, if I may ask you, there is always this question that there is potentially for olfactory groove meningiomas that could be both approached through eyebrow or pterional or endoscopic through the nose. Is there a different rate of preservation of olfaction? If a patient really wants to save the sense of taste and smell and they have a tumor like three centimeters, two centimeters that you could potentially save the olfactory nerves, would you lean more toward transcranial versus endoscopic or not?

- I would lean more towards transcranial because I think you have a better chance. I think it's probably harder to save olfaction doing an endonasal endoscopic approach. And in this case, we did save olfaction. We did not save one nerve, but we did have preserved olfaction with this one intact olfactory nerve. So if that's a big deal, and I think it is, olfaction is a very big deal for people. When they lose their sense of smell, they are not happy as you know. And so, I think that's an important discussion to have with them.

- Thank you.

- Okay. So, here's the post-op day one. A scan here that looks like a gross total tumor. Well, he's actually almost two years out now and has a clean scan with no evidence of recurrence. Here he is 15 days after. You can see his right eyebrow incision. There you go. Pretty good healing. So, what are the limits of this supraorbital approach? One of the issues is getting into the midline along the crista galli cribriform plate area here. This can be very difficult. There's a fairly steep valley here that you have to be aware of and if you really have a tumor that extends bilaterally across the way here such as in this olfactory groove meningioma, you may not be able to get all that. In this particular case, we were able to get it. But if this tumor had extended a little further over here, we would have done a bilateral approach, and I think that's important to remember. So keep in mind, there are these blind spots with the supraorbital approach and they include the area along the cribriform plate here. And now with a third layer of 45 degree endoscope, you can often see this area quite well and get to it but it can be a challenge. Also, over the sphenoid ridge here and under the ipsilateral optic nerve can also be very difficult to see because the approach is essentially in line with the ipsilateral optic nerve and there is really a blind spot directly under the nerve. Again, you can see some of this with the endoscope. But certainly, with a microscope it's very hard to see. And I would encourage everyone who's doing these cases to put the endoscope in every time to look around and get familiar with maneuvering endoscope in these sorts of cases. What about this case? So, this was a patient who came to us particularly requesting an eyebrow craniotomy. He had a receding hairline and he was a musician and he did not want a scar going back here. And I told him that this would be a challenge, that I wasn't sure we could get high enough. And we talked about it and ultimately, he wanted to go forward, and as did we. This is showing the setup with him in the operating room with the navigation. Now, you can see the sort of planned approach here, and this is mapping out where the tumor lies in his incision. Again, supraorbital notch and the extension to the eyebrow. So, this actually turned out to be a very nice approach. This is him a few days after surgery with our nurse practitioner. We got what we thought was a gross total removal. We dissected all the dura here. We reconstructed with a bone cement and he's now actually- He's almost two years out from his surgery. This is his one-year post-op and he has no evidence of recurrence at this point. So, I think those are sort of the limits of the supraorbital approach for extra-axial lesions from meningioma such as this in terms of how high you can go on the forehead and how medial you can go. So, what about intra-axial tumors? There's a very straightforward cases. It was a solitary metastatic melanoma. And you can see here, this is, I think, really an ideal approach for the eyebrow. This is the ideal tumor for use of the eyebrow craniotomy. It's really sitting on the floor of the frontal fossa here. And why don't we go to the video there? You can see that we've opened the dura and we're looking at some arachnoid there. We are localizing. We're trying to localize the tumor. And often, as it's often the case, you can't quite see it but we can see a little bit of staining of the melanoma right there. You can see that staining there where it's just barely coming to the surface. We've opened the cistern in the optical cistern. And so, we have nice brain relaxation. Again, no retractor is needed. And then we're just opening the arachnoid here and getting into the lesion. And really, the goal here, if you can, is to try and do a sort of pseudo capsular dissection. These tumors do have somewhat of a pseudo capsule and generally separating the compressed surrounding cortex. Notice that we have gel foam down below beyond our approach so we don't spill blood into the subarachnoid space. And using the Rhoton micro dissectors, just working around the tumor. This was a tumor that was small enough that you could really work around it. Again, a three hand technique. One of us is skewering the tumor with a nerve hook to kind of pull it away from the brain tumor interface and just pulling it in gently. But you can see there's very good exposure here in this, again, using the microscope. And we like to use the ring curettes. I guess I do too much pituitary surgery, but the ring curettes, you can see through them because they are hollow and you can do very nice dissection with the ring curettes. They're sharp on the inside and more dull on the outside and I think they're very good for these sorts of keyhole approaches. Now, you can see we're really at the bottom of the tumor here and we're, again, rolling it away from the surrounding brain. And a very straightforward case, but a nice way to do this through the eyebrow here and then reaching in and taking the tumor out. Almost in one piece. And then taking a good look and you'll see we'll bring in endoscope here. Here we have a 30 degree endoscope. We're looking at the resection cavity and you can see a nice, clean resection cavity, nice pulsatile brain. So, very straightforward use of the supraorbital approach. And I think it's an ideal route for these kinds of tumors. And there's the postoperative MRI. And we typically will do SRS to the resection cavity as this patient did and he's been clean now for I think over six months. And certainly, you can take out bigger tumors. I don't think the size matters too much in some instances. You know, this is quite a large tumor with metastatic non-small cell lung carcinoma. You might say it needs a bilateral approach, but really this is a tumor that can be removed through an eyebrow. And this is just the post-operative view three months after removal and SRS. And this patient obviously, eventually succumb to their cancer, but this is a very effective removal. I think in general, the advantage of the eyebrow approach is that there's very little muscle and scalp manipulation. Patients tend to recover very quickly. They don't have much pain and it really gives you a nice exposure into the frontal fossa. So, I think I've summarized these points quite a bit here. And I would just say that certainly in our experience, the neurological and overall recovery does tend to be quite rapid. They don't have much pain, which has potentially an advantage over the larger craniotomies, and you generally get a very good cosmetic result. Okay, so let's switch gears to the final two approaches that we're gonna discuss, the gravity-assisted transdural approaches. We're gonna just talk briefly about the transfalcine approach which we use for quite a few intra and extra-axial parasagittal tumors that are covered by eloquent cortex, and this drawing here sort of depicts the overall concept. You can use this for metastases, gliomas, even some meningiomas. And basically, by putting the patient with the lesion side up, the contralateral hemisphere will fall away and it really brings these pair of parafalcine lesions right to the dural surface. So, if this is primary motor, schemata sensory, you don't have to do any retraction here and allows you to sneak in and basically remove these tumors and preserve the overline cortex. And that's the basic concept. And I think that the real utility of the endoscope is providing this view that you, again, you will not get with the microscope. This can also be applied to the transtentorial approach for lesions of the temporal, parietal, and occipital lobe. Similar concept, putting the patient in a sitting position and doing a supracerebellar transtentorial for lesions that are essentially sitting on the tentorium or very close to the tentorium, a way to avoid critical visual fibers and other key areas. And certainly, we're not the first to use this approach. This has been described now almost 20 years ago by Dr. Goel and others. Dr. Broggi and his group, Dr. Ferroli have written about this gravity-aided transfalcine removal. And again, this is just the basic concept. By putting the patient in the proper position, you allow the lesion to be essentially facing a dural surface that you can get to without going through any cortical tissue or white matter. So, here's an example. This is a woman with a metastatic ovarian carcinoma. You can see there's quite a bit of edema here. It's fairly deep. It's directly sort of straddling motor and sensory areas. If you were to come down directly on this, you would probably cause significant harm to this overlying cortex. And so, we chose to do a right-sided approach going to the left-side of the tumor. So, here we are doing this transfalcine approach. We use the ultrasound obviously to help localize in addition to the use of navigation. So here, we've got the... We've done our dissection. We found the falx. We're using the Doppler again because of the possibility of vessels being pushed up against the falx by the tumor. And we've opened the falx now and you can see we're starting to remove the tumor here. And this was a fairly, fairly firm tumor. Again, we started with the microscope and then we'll use the endoscope at the end. And now we're using the endoscopic view and you can see with the 30 degree endoscope, you can see this sort of superior roof of the tumor that you really can't see with the microscope. And I think this is the beauty of the endoscope. And again, you have to have someone driving the endoscope for you. You can't do this by yourself. This is not one person surgery. You've got to have an experienced endoscopist. Hopefully, your partner or a seasoned resident can do this for you, or you can drive for them. But really critical to provide that view, that sort of up view, looking up into the resection cavity to avoid the sort of retraction and beating up the overlying cortex. And you can see this beautiful view that you get. We put a little muslin there. We had a little branch on an artery that was fine. And you can see, again, here is the end, just irrigating. You can see this very nice view, big defect in the falx and what looks to be a gross total tumor removal. It's a very nice approach for these sorts of cases. There's the post-op view. This was a lady who could not get contrast because of her renal function, but you can see the resection cavity the day after surgery. They're nice looking at resection cavity and there's our CT scans six weeks later. And she had an improvement in her motor function. Here's just another example. A patient with two metastatic bladder carcinoma, large frontal parafalcine. Met here with a lot of edema here. Really too big to do SRS on, in my opinion, and a smaller, deep lesion on the right. And so, we elected to remove the larger one through a right transfalcine approach and then did SRS to both of them. And you can see here, here's the resection cavity and then she got SRS and you can see this one got a little bigger but then they both essentially disappeared. So, nice use of this transfalcine approach. You can see here, the edema going down very nicely with the tumor removal and the radiation. And then finally, let's just talk about the supracerebellar transtentorial approach. And again, this has been used. It's been well-described by a number of people over the years. It has really not been described in any great detail with the use of the endoscope, and this is really critical in these cases that they'd be done, I think in a sitting position, if you do the sort of standard sitting position. This is my partner, Dr. Parker Darien, here at the initial. Beginning of one of these procedures, you can see this is really an uncomfortable operating position for many of us. And when you bring the endoscope in, not only can you see better, but I think you can operate better because you're so much more comfortable and you can really do a very nice job here. You can see Dr. Parker Darien here is holding the endoscope and I'm working the instruments here. We're using the navigation and it's a very comfortable operating position. So, I just want to show you one more example of the use of this case. It's a young woman with a solitary metastatic melanoma here. A lot of the edema in the optic radiations here. This is, in my opinion again, too big for radiosurgery, but it's a challenge to get to because you've got the optic radiations in the way. Fortunately, this tumor did come down to the tentorial surface here. One other issue which is an important thing to note preoperatively is there's a branch. The posterior cerebral artery running right through the tumor, creasing the tumor here. So really, a challenging case in a young woman. And I think this was really an ideal case for the sitting position transtentorial approach. So, there's the setup here and this is our fellow. You can see us operating here. You can see the light in the head there with the endoscopic view. But again, we start with the microscope. Again, the patient's in the sitting position, just generally bringing down the cerebellum. And using again navigation, very important here, and opening the tentorium. And in many cases, you can't quite see the lesion initially. But just with a little bit of dissecting through that, then the cortex we fall into the lesion here using up-angled bipolars. And then again, using the microscope here, we're doing the initial removal, piecemeal removal. Yeah, and I think the ring curates are very helpful for these sorts of tumors. As we get towards the mid and upper aspect of the lesion, we switched to the endoscope. And this is why. Look at the view we have now and you can see these branches of the posterior cerebral artery that of coursing to the tumor. Obviously, these must be saved. And so, you get this beautiful up-close panoramic view that you just cannot get with the operating microscope. Obviously, we left a little tumor behind that were taped on those vessels. But she went on to do very well with an improvement in her vision, stabilization of the tumor. We got a near complete removal, almost a gross total tumor removal. And then of course, she got SRS to that area. That's her post-op. This is her post-op day one scan here. You can see the vessel here enhancing the resection cavity. And this is her the day after surgery, actually feeling quite good and happy. And this is her three months and she's now almost two and a half years out. She also got Ipilimumab which as you may know, is a very good immune modulator for metastatic melanoma. And she's now more than two years out and is tumor free. So, she's done very well.

- Excellent. Excellent zoom.

- And then just another example. This was a cavernous hemangioma in a woman. You can see the lesion here. She had a severe headache while snowboarding. You can see typical lesion but the important thing is here, very close are essentially touching the tentorium here. Coming in laterally would really threaten vision. And so, we thought this was another very useful application of the transtentorial approach. We you did fiber tractography on her. So we knew where the optic radiations are. We knew this was really not an option coming this way, and so we went from below. And you can see the resection cavity there, and this is just the day after surgery. So, I think this is a great option. Again, the endoscope is essential for these transdural gravity assisted cases because otherwise you're just not gonna be able to see up into the resection cavity well enough just with the operating microscope. So I think in summary, I hope I've tried to demonstrate to you the utility of these keyhole surgical approaches and how important I think endoscopy is for almost all of them. And I think the use of the endoscope combined with better instrumentation, our enhanced anatomical understanding, navigation, et cetera, we can really apply these to many, if not most intracranial lesions. But I would say I wanna emphasize I think the endoscope and the microscope are very complementary. I think it's important for people to try and use the endoscope in intracranial cases and get more comfortable with it. Lots of people are doing that and they're certainly not mutually exclusive visualization modalities. And then finally, I wanna just stress the importance of teamwork and collaboration to achieving success with these techniques. Thanks so much.

- Thank you. Thank you. It was a great talk. We really enjoyed the nuance of technique and the pearls. Again, we appreciate your expertise.

- Okay, thanks again.

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