Grand Rounds-Endoscopic Craniofacial Resection of Anterior Skull Base Tumors

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- Hello, ladies and gentlemen, and thank you for joining us. This evening, we're privileged to have with us, Dr. Nicholas Coppa from Oregon Health University Sciences Department of Neurosurgery. He's a neurosurgeon with specialty of endoscopic surgery. We're very excited to hear his thoughts tonight on endoscopic craniofacial procedures. Nick, thank you again, and we're very much looking forward to your talk.

- Dr. Cohen, thank you very much for the opportunity to participate in the double ANS Operative Grand Rounds. I've watched each episode with enthusiasm, and it's a pleasure to be here-

- Thank you, Nick.

- I'm gonna talk about endoscopic craniofacial resection and my objectives for this discussion, to really establish the relevance of using this technique when performing craniofacial resection. We'll review a basic understanding of the relevant anatomy of the anterior skull base as visualized during the procedure, and then lastly, demonstrate our technique of craniofacial resection with an emphasis on feasibility, adaptability, and reproducibility. This is our team one neurosurgeon and three ENT surgeons. It's extremely important to work with an excellent team of ENT surgeons. This is a reference from the 1960s just to provide a historical perspective. This is markedly different. What I'm proposing this evening, as far as the technique, the treatment policy within this region. The indications for craniofacial resection, to treat malignant neoplasms involving the cribriform plate, lesions such as esthesioneuroblastoma, carcinomas of the paranasal sinus, including lesions that either approach but not invade the skull base or dura or those that have dural transgression and may in fact involve the brain to some degree. Surgical considerations when applying the technique include achieving an adequate oncological resection, minimal brain retraction, avoidance of injury to critical neurovascular structures, adequate reconstruction of the anterior skull base is on the forefront, particularly with most recent advances, and then lastly, now the patients are concerned with optical cosmetic outcomes and we need to take that into consideration as surgeons. Traditional craniofacial resection can be considered a fairly morbid procedure. Morbidity usually centers around a frontal lobe injury which includes brain contusions, frontal lobe edema that can clinically manifest itself as mental status change, cerebrospinal fluid leakage and pneumocephalus, meningitis, vocal soft tissue infections, which can result in osteomyelitis of the bone flap, delayed mucocele formation, or even cranial nerve deficit. So these are the morbidities that have been associated with traditional technique and we have to apply newer techniques in light of those. So what is our experience? We started incorporating these techniques into our practice in 2010, we have a N of 60, then you can see in this exploded pie chart that 27% of our cases include sinonasal cancer, esthesioneuroblastoma. The approaches to the ventral midline skull base had been broken down into transcribriform, transplanum, transsphenoidal, transclival. In that categorization, 28% of what we've done has been transcribriform so craniofacial resection. And I attribute that largely to the strength of our ENT Department and the referrals that we get from them. So what are the advantages of doing it endoscopically? Provides a direct route to the lesion of the sinus cavity. The endoscopes, particularly the angled endoscopes provide a wider field of view, has minimal brain retraction, minimal manipulation, and hopefully as a result, minimal neurological morbidity, is reduced risk of cranial bone flap osteomyelitis because there's no craniotomy that's performed. So there's no pre bone graft that's replaced at the completion of the operation. Whenever you incorporate a new technique into practice, you have to evaluate your results and look at things in the context of operative time, extensive resection, incidents of CSF leak and other morbidities, hospital length, and then the new cranial neuropathies and neurological deficits, and then lastly, patient comfort. Craniofacial resection has undergone evolutionary process. Those transcranial, transfacial approaches are now evolving to transnasal approaches. We've avoided disfiguring incisions on the face. There has been a complication reduction relating to meningitis, CSF leak, pneumocephalus, improved technology in operative techniques, description of anatomy approaches, high definition endoscopes for illumination and visualization, frameless navigation. All of these things have enabled us to perform these operations safely and efficaciously. Harvey Cushing who's long thought to be one of the major contributors to pituitary surgery. In 1914, when describing it, he wrote that he made no claim for originality and it's important that I make the same claim today. There's been several centers, not only in the United States but the world that really pushed the envelope with the incorporation of endoscopic minimal invasive surgery into neurosurgery and they deserve most of the credit. I just want to put an emphasis on adaptability in incorporation of those techniques into your practice. So what are the special considerations of performing this operation? You need to have good equipment. You need endoscopes, you need high-definition cameras, good illumination, a high-definition monitor. Some of our videos will be, that we'll show, were done in high-def and others in standard definition and you'll begin to appreciate the difference in quality and how important it is to have high-definition so you can see what you're doing with great resolution. You need instrumentation from the ENT world to clean your endoscope. Microdebriders to remove sinus mucosa and even malignancies within the nasal sinuses. Minimally invasive drills are important, several different varieties. I tend to use the 10-centimeter and 15-centimeter straight attachments. It's enough length to perform the osteotomies of the anterior skull base while allowing your hand to rest on the patient's chin so it gives you stability. I tried these longer curve attachments and I just felt like my hand was free-floating and I had no stability. So for me, 10-centimeter and 15-centimeter attachments are the way to go. Insulated Colorado needles are used to harvest nasoseptal flaps and close off of the nasal septum, and suction cautery is also important because being close of the paranasal sinuses has a very rich vascular supply and can bleed. This is also good for coagulating tumors. Micro instruments are a must. Mechanisms to coagulate, cautery, pistol grip, bipolar cautery has been used in sinus surgery and this is an instrument that was unfamiliar to me at first but again, you have to get familiar with your equipment so you know how to use it and when to use it. We navigate off of CT angiography. The CT angiogram provide very detailed information about the bony anatomy, the destruction of the bone, the relationship of lesions to the vascular structures, and we prefer it over MRI. So general considerations, obviously this is done under general anesthesia. You need to communicate with your anesthesia team. You need to tell them to get good vascular access and arterial line, blood should be typing cross-matched, and the reason is that, you know, malignancy in this region can be quite bloody. The operations can be quite long so, you know, no surprises. The blood loss can sometimes come very quickly and it's good to be prepared so communicate with your anesthesia. The prophylaxis ceftriaxone and we continue that medication two grams daily while the nasal packing is in place, and we do not use lumbar drains as part of our operation. You position the patient like you position a patient for bifrontal craniotomy. You need to be prepared for that bifrontal incision in the event of an uncontrollable event endoscopically. We always prepare the right lower quadrant in anticipation of back graft. We get to use it but it's good to have access to it if you need it. It also enables you to get some fascia from the rectus sheath. I position the head in extension. Remember we're looking up towards the frontal sinuses and the cribriform plate so head extension is preferred. I do lateral bend so I bring the patient's left ear to the left shoulder and I turn the patient so that they're looking at the surgeon, and a lot of that is aimed at surgeon comfort. You don't want to be leaning over into the surgical field and leaning into the patient throughout the duration of the operation. It's abandoned that traditional concept of keeping the patient parallel with the floor and the roof and the sides of the walls, but with anatomical orientation, frameless stereotaxy and patient comfort, I think you're better suited. This is an operation underway. You can see there's plenty of monitors for visualization, not only for the operating surgeon and navigating surgeon, but observers in the operating room. The scrub stands behind the surgeon with the instrumentation. And this is two surgeons operating simultaneously. So pre-operative imaging, what do I look at? I assess for bone and dural transgression and the presence or absence of brain invasion. I assess orbital involvement in anticipation of the potential need to resect the lamina papyracea or the periorbita. I assess the laterality of the lesion because that's gonna determine what side of the nasal septum we harvest our vascularized nasoseptal flap from. I also look at the interior-posterior extent of the tumor because that's gonna dictate where I need to make my osteotomies. The nasal cavity anatomy may not be on the forefront of everyone's mind, particularly in neurosurgeons, but it doesn't hurt to review. In the midline, you have a bony cartilaginous septum which is comprised of the perpendicular plate of the ethmoid and the vomer and the anterior septal cartilage anteriorly. Laterally, we have a superior middle and anterior turbinates and underneath which, the paranasal sinuses drain. Most of this tissue is gonna be resected during an operation.

- Hey Nick, can I please ask you to activate your arrow so you can sort of let our viewers know the details so you can point at them please. Thank you.

- That visible?

- Yes.

- Expanding on that, the blood supply. The blood supply, it's a very rich and anastomonic network of blood vessels and the blood supply comes from both the internal carotid circulation and the external carotid circulation. The anterior and posterior ethmoidals come from internal carotid circulation and they anastomise both with vessels of the lateral nasal cavity wall and the midline septum. Sphenopalatine artery here which is a branch of the external carotid circulation provides the vascular pedicle of our mucosal flap on nasoseptal flap that we use for reconstruction. The bone that separates these cavities is pretty thin. The cribriform plate, it's been the fovea ethmoidalis which is the transitioning point between the anterior skull base just above the orbit. The lamina papyracea separating the nasal cavity of ethmoids from the orbit. All these structures are thin and that is important and relevant when doing your osteotomies. Never want to exert a lot of pressure on the drill. If you're using a blunt instrument to flick off a piece of bone, you need to be gentle because the bone can give away suddenly and you can plunge and what's not what you want to do. So which structures are removed? Essentially, every operation is reduced to the same thing. You want to remove the nasal septum, remove bilaterally the middle and superior turbinates. The anterior and posterior ethmoid air cells removed bilaterally. We performed wide sphenoid opening bilaterally, opening of the frontal sinuses, we resect the crista galli, the cribriform plate, the dura of the anterior cranial fossa, and lastly, the olfactory bulb and tracts. So knowing that that anatomy needs to go is very helpful. It moves things along during the surgery. So let's talk a little bit about how we do it step-by-step. The operation begin with just putting your inner scope in and exploring the nasal cavity. In here, you can see the endoscope has been inserted into the left side or through the left nostril. You have the middle turbinate here laterally, and this is the nasal septum medially, and we have, I believe, would key us to a video. So just take a look around, look at the normal side, look at the abnormal side, get a sense of your integrity of your mucosa that you're gonna use for your pre-flap. Here, we're injecting epinephrine with lidocaine, excuse me, lidocaine with epinephrine. You know, this is very standard in sinus surgery and you can see how it bleaches the mucosa. That minimizes oozing from the mucosa. So the next step is resecting the middle turbinate and this is done on the side that you're gonna harvest your nasoseptal flap from and it enables you to have more visualization and the moveability of your intremies. So we have a video for this step as well. So we're mobilizing the turbinate heat permanent attachment, and we're making an opening of performing a maxillary antrostomy, again, on the left side. Make a nice opening to avoid an outflow obstruction from that sinus. This is using a microdebrider to remove some of the mucosa. Again, lateral to that turbinate route, and then you bring in your scissors and you just come straight across the root of the turbinate and push down, and that is pretty effective at resecting it in one piece and you can save that mucosa for later in the operation. If you need a little piece of autologous tissue to augment your reconstruction, you can use healthy mucosa from the middle turbinate. So let's go back to the next step. The next step involves harvesting your vascularized pedicled nasoseptal flap. And the illustration on the left comes from a reference from doctors Kassam, Carrau, and Snyderman. They elegantly describe the technique for a nasoseptal flap harvesting and reconstruction. It was done an operative neurosurgery in 2008 and we adopted the same technique. We've used it and it work for us very well. The purpose of this or the principle of this is to get a nice piece of healthy mucosa that we're gonna use to cover a defect in the anterior skull base. And again, the vascular pedicle for this tissue is the sphenopalatine artery. So the illustration here is putting the endoscope into the right nostril. So the turbinates are coming off the lateral wall intercepting the midline. And you have incisions in that mucosa. The inferior incision is gonna come along the transition between septum and hard palate and it goes back towards the choana. The superior way of that incision comes just below the sphenoid ostium here, and you can see that it maintained on its vascular pedicle of the sphenopalatine artery which is mirrored right here. When you get into that plane between the mucosa and the nasal septum, utilizing a blunt micro dissector, you can remove it very efficaciously, and then when you get to its root of the vascular pedicle, you begin to remove the nasal septum so that you create one cavity to work in posteriorly depth of the exposure, and here, you're looking at things at the sphenoid sinus. And that tissue is used to cover the anterior skull base defect. Here, you can see the insulated colorado tip needle. We're starting posteriorly at the depth. This is the hard palate, this is the choana, and we're making the inferior mucosal cut. One has to be gentle because, you know, sometimes you can actually cauterize through the nasal septum. This is the sphenoid ostium here, and our superior cut starts just beneath it. And then we're gonna come along the nasal septum at the level of the middle turbinate. And you come straight out towards the tip of the nodes, and then you connect those two ends, and then you just come straight out. Here, we have a blunt micro dissector getting into that plane between the nasal mucosa and the bony cartilaginous septum. If you're in the right plane, it separates quite easily and again, you work from anterior to posterior or superficial to deep. And now the pedicle flap is now mobilized on its pedicle. It's gonna be stored inferiorly here as we shift our attention higher up in the nasal cavity. So the next step after harvesting your nasal septal flap is to really complete your nasal septectomy. You also want to open your sphenoid sinus widely. And the importance of this is really to visualize the familiar anatomy, more commonly seen by us, which is the sellapher and really that curve as you go from sella bone, down to the tuberculum then to the planum. So that will provide important anatomical structure for localization throughout the operation and we have a video of this as well. So here, we're back in the nasal cavity, the nasal septum has been removed. We're looking at the rostrum of the sphenoid sinus right here so the sphenoid has to be open. It hasn't been opened yet. So you can see we're now operating in one compartment. This is after everything's done, a wide sphenoid opening, ethmoid ASLs have all been removed so we're looking at anterior cranial fossa here. This is the region of the planum. Here, you can see we're pushing on a periorbita. The laminate papyracea has been removed partially. So it's important to open things widely so that again, you maintain a constant reference point throughout the operation in the way you want. We have frameless stereotaxy but you can often use anatomy to get your bearings. And then here you can see the nasal septal flap. So the next step is dealing with the ethmoidal arteries. You need to find both the anterior and posterior arteries on both sides, and oftentimes, they're covered by some bone that requires drilling away, and once the bone is removed, you coagulate them and divide them. So here, you can see I'm not using that pistol grip bipolar. I'm using just a regular bipolar because I'm very comfortable with that and that's what I like using. In oftentimes you can work with it through one nostril. You can have the tips open up wide enough so that you can still use it. So we removed it from the bony casing and when we cut it, you want to be careful to leave a stump. You don't want that artery to retract and continue to ooze that can result in a retrobulbar hematoma, and you don't want to have any ophthalmologic problems or complications when you cut the arteries. The next step is doing your osteotomies and again, I use a high-speed drill with minimally invasive attachments the 10 and 15-centimeter attachments. This is a very tactile process. Remember the illustration at the beginning, the bone is very thin. It's okay, if you go through the dura and you get some spinal fluid leaking out. That dura's gonna be open and removed. So for orientation, this is the patient's left fovea ethmoidalis, this is the planum, this is the right fovea ethmoidalis. And it's just a constant stop and go, stop and go, feel with the drill, thin the bone and out and be patient. Irrigation, we typically use a lot of irrigation when drilling in neurosurgery. With endoscopic drilling, irrigation can be important if you're around critical neurovascular structures. However, the more you irrigate, the more that drill is gonna spit that irrigate back into your endoscope and obscure your lens so it's a balance between keeping things cool and avoiding the need to clean your lens constantly. So the next step is drilling anteriorly. This is a little bit more tricky because you have to, you know, just behind the cranial sinuses, which have been open and the crista galli is often in this region so that's an area of thick bone. You're transitioning from the thin bone along the planum, the thin bone along the fovea ethmoidalis, and the bone gets a little bit thicker anteriorly beneath the crista. And it's just this constant drill, stop, drill, stop. Sometimes, when it gets thinned out and you can just put a little traction on your perpendicular plate, and then just crack that last bony attachment. Osteotomies are complete, and this is really what you should be left with. There's a video of this. You'll have a floating island of tissue and visible dura circumferentially around the tissue that needs to be resected. You can see the pulsations in the brain, minimum dura around this, and then at this point, this is what I, we want to reduce the central bulk of this tissue. The more bulk that we leave behind, the more difficult it is to make our dural cuts and manipulate this. So try to reduce it and you can use suction bovie to kind of coagulate and reduce the volume of that tissue and that can be done safely in that location. You don't want to work with a bulky component of tissue centrally. So the next step is making your dural cuts. Chances are with the drilling, you're gonna have an opening in the dura somewhere and that's usually where I start. I tend to make, the last general cut that I make is along the planum. And with what I've done here is that, this is an instrument from sinus surgery. It's called a sinus seeker, has a ball tip probe on the end, and I insert it through one of the dural openings. I pull the dura back away from the brain, and then I use a sickle knife and you can see with that sickle knife, you can actually make your dural cuts pretty quickly and pretty safely. I feel that I have more control with a sickle knife using that technique than trying to get angled micro scissors in that region to do the cuts. Once the dural opening large enough, you have space to fit the cottonoid patty between the dural and the brain and that not only will dissect the brain away from the dura, but it protects the brain from the sickle knife so that you don't plunge. But here, you can see we positioned this of a half by half patty positioned between the brain and the dura and I can go a little bit more quickly with my sickle knife to complete those cuts. I'm dissecting with the sinus seeker. I feel with this technique, you have excellent control and it's less awkward than using micro scissors in my opinion. the next step is dissecting the crista away from the falx. So this is a snapshot earlier on and an experience. Now, before I begin making my dural cuts, I make sure that the crista galli has been completely removed. All you need is a blunt micro dissector, and you can dissect the attachment of the falx away pretty easily. Once freed up enough on both sides, you can grab it with a pituitary and twist it out of that dural sheath. So the last thing is completing the resection of the cribriform plate and dura, but lastly, as you pull that away, you'll make that posterior cut. This is somewhat staged. This is more of an illustration that you can see the tissue. That's the tissue that's removed in block. The olfactory bulb and tracts have already been removed but the patients in time, you can see this essentially no manipulation of the frontal lobes, no retraction. Once that's done, you inspect your frontal lobes. Look at your margins depending on the pathology that you're treating. So this is a sphenoid sella, a planum, orbit, orbit frontal sinuses. Fovea ethmoidalis here, fovea ethmoidalis here, then depending upon the pathology where it's infiltrated, you'd take pieces of the dura just to make sure that there's no dural involvement. Can we do that and we get those results before we start reconstructing. So the next step is reconstruction and it starts with placement of the intradural, dural substitute graph, you duragen, of the suturable duragen. So this is the completion. You can see that the DuraGen is placed, it's sandwich between the frontal lobe in the basal dura. You want to use a graft that's larger than your defect because you want overlap. The whole point for the frontal lobe to come down and sandwich that dural graft in the base of the skull. And it's important to keep the mucosal surface towards the nasal cavity. With a carefully prepared graft, you can get enough overlap so that you can completely cover and obliterate that defect the whole been in place with a combination of surgicel or surgicel avitene mixture, and that's reinforced with the tissue. So that really concludes the steps, the step-by-step approach to how we do the operation. Why don't we, you know, apply these principles with specific case examples. So case one, this is an example of sinonasal melanoma. It's a 71-year old woman who presents epistaxis and nasal congestion, she underwent biopsy at an outside institution, she made, the diagnosis of melanoma was made. A PET scan was performed but it did not show any evidence of other foci of disease, and she was indicated for cranial facial resection. Now, this is done with a high-definition scope and camera, and I think you'll be able to appreciate the difference in image quality and how helpful it would be to perform surgery with high-definition equipment. This is sinonasal exploration, we're injecting. This is what the camera in the patient's right nostril, moving some mucosa. This is gonna be where we harvest our vascularized pedicle flap from. Resecting the middle turbinate. Again, we're making a room to work and this is through the patient's right nostril. This is the healthy side. Removing one mucosa with the microdebrider. Now, we shift over into the sides, the side with the tumor. This is all tumor scoped through the left nostril, and we're reducing the bulk of the tumor with the microdebrider. So this is piecemeal resection, which is okay. This is disease nasal septum on this side. Remove that nasal septum, remove that ethmoids, we divide the ethmoidal arteries, and we're looking at anterior skull base. This is the front, you know, not only the drill, you can do the kerrison to complete your osteotomies. It's also a good blunt instrument to palpate. Once your osteotomies are complete, you have that pulsating island of tissue and you begin to make your dural cuts. So here, we're on the right side, okay? We made our dural opening, we're protecting the brain with our cottonoids, connect this dural opening with the dural open here more anteriorly. The technique I like to use is a combination of that sickle knife. For me, it's very control and I think that it's safe but you should also have micro scissors at your disposal because there's a role for them too.

- How do you deal with the tumors that are larger and extend laterally, Nick? Do you use ring curettes? if they're going to-

- Flat tumors, you know, in my experience, we haven't done anything that comes lateral up and over the orbit, but if there's tumor involvement, usually I'll dissect on the side. Let me pause this for a moment. Is it possible to pause? So with something that's a little bit larger, you want to start on the healthier side because you want to open up and create visualization that will help you with the disease side. Once the dura is open, the intercranial component doesn't necessarily have to come down with the dura. You can leave that behind and then take that out in the second piece.

- And you use ring curettes to-

- The important thing- Once that you can play that video and cue it up, but once you start to open that dura, you can see that there's small vessels that bridge from the frontal lobe that are adherent for the dura and the falx and you don't want to pull, you want to coagulate, cut and then I think it's important to put your cottonoids between the brain and the falx. My opinion, this is probably the most challenging cut. We know that sometimes they can be venous channels here in the falx as they attach to the crista. So coagulation, again, this is a standard bipolar cautery here. You know, you have so much room to manipulate the bipolar that I don't necessarily use the pistol grip. But once you've opened up your dura and you're just left with the falx, you want to put your patties between the frontal lobe and the falx, and you want to make this cut in a very controlled fashion. The presence of the patties ensures that your tips are protected and you're not gonna cut through any of those attached vessels that could be adherent to the falx. We can see how everything is done under direct visualization. And then you use that sinus seeker it's a great blunt instrument. Once you've made that anterior cut through the falx, everything now will just fold away and be attached by that dura along the planum. This is the olfactory bulb and tract on the right. Here, we've left it attached on the left and then we make that final cut. And now, we will have specimen that would send to pathology. You take the bulb and the tract. This is a great instrument for dissecting. And we will also send dural specimens. So we're done with the craniofacial resection component. Now this particular patient, you know, it invaded the periorbita through the lamina so before turning our attention to the orbit, we want to reconstruct and I want to place that dura graft. You can see that the size of the dura graft is not a little bit larger than the cranial opening but somewhat significantly larger because I want to sandwich it in between the frontal lobe with the base of the skull, and the sinus seeker again, is a great instrument to do that. Then you can see how the brain is gonna push that graft down circumferentially to form a seal. So once in this particular case, I've actually augmented it anteriorly and posteriorly with another piece if you don't want it a little bit more extension, but once that's done now, we're gonna turn our attention to... This is the left periorbita and because the MRI scan of the tumor radiographically invaded this region for the sake of completeness and negative margins, we cauterize that periorbita and orbital fat, and it's resected. Despite the amount of protrusion of fat into the nasal cavity, postoperatively, the patient had orbital swelling but once the swelling subsided, there was no complaint of double vision. So resective surgery is done. Now, it's time to continue the reconstruction. In here, you can see we're getting at pedicle nasal septal flap up over the defect, mucosal side out and it's reinforced with Surgicel, Advitene Surgicel in the tissue build. This is back to the MRI. So that's that case. The second case, is a 65-year old woman, similar complaints. Had a visible mass in the nasal cavity, came back as squamous cell carcinoma. A PET scan showed no evidence of nodal and metastatic disease and we performed craniofacial resection. Here you can see is actually bony and dural transgression in small amount of brain invasion. The bony defect you can see on a CT angiogram. So we're anticipating. All the sinus work has been done. The dura has been open here. I'm using the pistol grip now. In my opinion, it's a little bit more clumsy for me. So we're doing that challenging cut of the falx. It's still a little bit bulky here. You can cauterize that down a little bit more if you like, but what I'm trying to define is the space between the frontal lobe and the falx. I just don't want to blindly put my scissors in there and cut because there can be small vessels inherent to the falx and I try to avoid that. So blunt dissection, placement of patties for protection, once your patties are in place, then you can take your micro scissors and complete that cut with some cautery as you go. So cauterize, cut, cauterize, cut, and you want to see your tips. I struggled a little bit here seeing exactly what I was cutting, and rather than just putting my tips further and further, I took my sinus seeker and I did a little more dissection. So you can see just the brain and the small vessels attached. You hear that sinus seeker. Once I have that sinus secret under the falx, I know my cut is almost complete, and then you're home free. And once that's done, you can peel it down. Now remember, with dural violation and some brain invasion on the left side and we're gonna be able to see that here. It's not a huge amount. The healthy side, not healthy side. Let me see is cuma. And it looks some blunt dissection. There's no fat involved in tract on the contralateral side. Returning back to the tumor, you can see how it separates from the brain. Although it's blunt dissection, it's not just pulling. You see these vascular attachments, little cautering, they're very helpful. Our last attachment posteriorly. It's important not to release that too early in the operation because if you think about it, if you release it here, everything is gonna really fall into your endoscope so this actually kind of tethers the entire specimen up until the very last cut. It's the specimen with that tumor. I take a look back at the frontal lobe and do some cautery, and this patient would obviously go on and get radiation. So inspecting, we set margins around this area of the dura and frozen came back as negative for malignancy, and then we reconstruct it. So this is a case of esthesioneuroblastoma. It's a 48-year old woman. She presented with epistaxis and nasal congestion. Imaging confirmed a mass and at an outside institution, she underwent biopsy. So this MRI and the CT is post-surgical. You can see they operated on the left side, opened up the maxillary sinus here, but this is the lesion and she was referred to us for craniofacial resection. So this video is gonna emphasize a little bit more of a drilling. You can see this is not high-definition. Just look at the difference in the quality of what you can see. The resolution, in my opinion is poor. This is anteriorly just behind the frontal sinuses and you can see how it's stop and go. Every time you stop, you just want to take a feel because the bone is very thin. Same thing along, this is the left, fovea ethmoidalis This is central, I mean, in theory. Just coming inferiorly. In my opinion, to use those curve long drills, you know, if your hand is not rested solid on a patient's chin, I think that drilling can be very dangerous with respect to plunging. This is a central bulk that I like to get down and mass a little bit more before I turn my attention to the dural cuts. This is probably the most difficult area drill because the bone thickens a little bit right there, and you don't have to go complete, you can bend and then maybe a little kerrison or crack it to complete that bony cut. We have a floating island to bone and with a blunt dissector or that sinus seeker, I'd block off as much bone as possible including the crista. So here you could, basically, we're making a dural opening to the small opening. I use that sinus seeker and my sickle knife, but you can see that every operation has reduced to the same basic steps over and over again. We know that the tumor was predominantly on the left side which was this side, but you know, it doesn't necessarily change what we have to do. We know that all this tissue needs to be removed. I think your earlier question of how you handle the tumors with the more intercranial extension is a very valid one and still, you know, try to define a plane between the tissue and that intracranial component so that you can at least remove the bulk of this tissue and then turn your attention lastly to the intracranial component and dissect it away from the brain.

- So you actually do use ring curettes on the sides, Nick, in order to remove the tumor there, sort of hiding under the gutters?

- I haven't done anything that extends up in lateral over the orbit.

- So those you do through a bifocal craniotomy?

- You know, that's a good indication, in my opinion, to do a craniotomy because you can see, even though you have great visualization here, you really can't see above the orbit. The orbit would be right here.

- Sure.

- But to see above and over that orbital roof, I don't think you can accomplish that with these scopes.

- So this is primarily indicated for lesions that are confined to the sinuses, really hold their poles go parallel to the midline of the sinus. Is it, am I correct?

- In my experience, that is correct.

- Thank you.

- And then the last case is gonna illustrate what you can do with a bigger tumor. So this is a patient, she's 77 so she's a little bit older and she presents with outside institution with headache and this was her imaging. She underwent a sinus biopsy, she underwent biopsy and the pathology that institution actually came back as sinonasal undifferentiated carcinoma and she was sent to us for further opinion. And when we re-reviewed the pathology and our pathologist thought it was actually esthesioneuroblastoma and the decision was made to start with chemotherapy. So she's had two rounds of chemotherapy and you can see how the lesion shrunk like from this and this to that and that. The intercranial component shrunk, the nasal component shrunk. She was doing well clinically and we elected to proceed with craniofacial resection, but again, to answer your earlier question, you can see how that tumor didn't extend lateral to that medial orbit. That would be a good indication to do things open if there's intercranial lateral extension. And this is really at the end of the procedure where, you know, we resected the bulk of the tissue here. We left that intercranial component attached to the brain and then bluntly dissected it out in the second piece. I wish I had video of that, unfortunately, I don't. But that was the technique that we employed. This really shows you that the reconstruction in a little bit more detail, I find it easy to place the graft first anteriorly and laterally, and I usually do the posterior portion last. A lot of overlap and then a good vascular flap that cover that. There, you can see we're gonna be a little bit short so we used some additional material to reconstruct and cover that defect, and she did quite well. That concludes my video presentations and experiences, and again, my goal was to go through things in a step-by-step fashion and just illustrate with some cases, in each case emphasizing a different point of the technique.

- Thank you, I think these are technically superb videos. My question for you is, what's the risk of CSF leak in these cases, Nick?

- So in our experience, we've had two patients that have gone back for problems. Not so much with leaking. We find that recently, these two patients, and even in some of our, pituitary patients, it's not a leak but it's a pneumocephalus that is problematic. So there's no cracks, CSF rhinorrhea usually come back with some altered mental status, some lethargy, and CT shows pneumocephalus. So what I think is happening is that there's a small defect somewhere along the perimeter of the reconstruction enough such that they can get air intracranially but then the brain immediately falls down and obliterates that defect, has that ball valve operated. So we haven't had CSF leak, but we've had two pneumocephalus that have acquired revision, and the revision is included just augmentation with some 3D PhonoGraft.

- And so you're saying the chance of CSF leak is very small, but how about if a patient comes with a leak, do you put a lumbar drain in them and see how they do for a few days with them and then clamp it and see if they will leak again?

- Not usually. If somebody came with a leak, we take them to the operating room re-explore and you know, a lot of the strategy of dealing with CSF leaks, in our experience, a lot depends on the pathology that you treated. Is it a post-pituitary operation leak? Is it a spontaneous CSF leak? And with some revisions to the area so, you know, we have kind of a pretty well thought out algorithm, and a mind of what we do. I think the vascularized nasal septal flap is great at repairing things. If you go back, if you present with either pneumocephalus or a leak, go back and take a look. If the defect is small, see if you can augment it. If there's any concern, augment it and put a lumbar drain in. If it's somebody that's had several surgeries and it's still problematic, if the spinal fluid is clean, we'll put a lumbar parts and we'll shunt it. Rather than just trialing them in the hospital for a few days, you know, we'll, put a LP shunt in. This way, it kind of gets them through the system a little bit more quickly, gets them out of the hospital a little bit more quickly, and you get the benefit of extended CSF diversion.

- Sure. How about, how do you augment this when you say, "When we go in there and re-augmented," you remove extra pieces of a mucosal flap and that's how you augment them, Nick?

- So you can use mucosa, from mini cauterized surfaces of the nasal cavi. You can use alloderm which is kind of a synthetic thing. I've learned a lot of that from my ENT colleagues who are great in this area particularly our rhinologists who sees... You know, the rhinologists, they do a lot of spontaneous CSF leak repairs that neurosurgeons aren't even really aware of. And I learned quite a bit from him with his techniques, the concept of that Surgicel and Advitene mixture form like a paste and that's really good for cementing things and holding things in place. I learned that from him, but using alloderm which is a synthetic covering that we just bolster over the entire reconstruction.

- Any other complications that we should be aware of with this procedure?

- I emphasize a lot about dissecting the frontal lobe away from the falx so that you can, so that you don't accidentally lacerate some of those vessels that are inherent to the falx. One of our earlier cases, I get into some bleeding that really just couldn't satisfactory coagulate. So my strategy was, "Well, let me put some gel foam there and try to tamponade the bleeding so that it would stop, and then I continue with the operation and we did continue with the operation. When it came time for reconstruction, in all of these examples, you could see how the frontal lobes were pulsating. Everything looked relaxed. You can see space between the frontal lobes and, you know, the anterior cranial fossa. Well, in that particular case, the frontal lobes are herniating out through the cranial opening so I knew that there was a problem. I was concerned that there was a problem. When we reconstructed, in his post-op CT, he had a subdural. So he was bleeding beyond what we could see with the endoscope. You know, although our visualization is great, although we have angled endoscopes, we can't see beyond the bony opening, you know? You talk about lateral extension. If you can't see it, you know, if bleeding is happening, we may not be able to see it. So that patient had a subdural, had to be taken back for cranial subdural and he did okay, but you know, the learning point, control, try to prevent bleeding if you can. If you get into some bleeding, control it early, because if it is ongoing ooze, you may not see where it's collecting and it can be a problem.

- So the major- Oh, go ahead.

- We haven't had any infection, no meningitis.

- So you would say the majority of complication is potential pneumocephalus because of the ball valve effect, potentially CSF leak, potentially subdural bleeding. Those are really the major ones that our viewer should be aware of. Really tackling the tumors that are within their reach. Don't sort of go beyond the limitations of your approach and try to sneak in around the edges and cause bleeding. Remember that, just focus on what's in the midline and those are the tumors and should be selectively chosen for this and not the tumors that are large or they should be approached with craniotomy for the safety of the patient. I think those are the details. I mean, this is a beautiful technique. Definitely minimal frontal lobe retraction, beautiful view for patients will harbor tumors of appropriate size, and you have to remove all this space of skull involved anyways, and you will do that during the endoscopic approach without creating another craniotomy with its sort of limitations and complications. So I wanted to really thank you very much for a beautiful procedure, innovative. I know you have sort of taken little bits of new answers from other folks and develop sort of your niche, which is very respected. I want to really thank you and we really enjoyed listening to this session.

- Thank you very much for the opportunity to participate. And I couldn't agree more with your summary of the points that I wanted to get across. And lastly, you know, many thanks to the institutions that pioneer these techniques and brought them to us so that we can incorporate them into our practice.

- Thank you, Nick.

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