Cavernous Sinus: A 38 Year Journey

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- Colleagues and friends, thank you for joining us for another session of the Virtual Operating Room. My name is Aaron Cohen. Our dear guest today is Dr. Atul Goel from Lilavati Hospital, India. He is one of the most innovative minds in neurosurgery, an incredible surgeon. Has truly contributed significantly, not only to the literature of neurosurgery, but also in leadership roles. I'm so honored, Atul, to be with you today. I know you're gonna talk about an exciting topic, and that's resection of cavernous sinus tumors. A controversial one, but a very important one. So I'll love to hear your thoughts and learn from you, and please, go ahead.

- Okay, Aaron. Needless to say that I'm extremely honored, and it is my proud privilege to be on your show.

- Thank you.

- I've given lectures on cavernous sinus for last 30 years at least, or maybe more, but this one is the one. And I'm looking forward to be on your show, Aaron.

- Thank you again, it's an honor.

- So, cavernous sinus. I have been involved in this beautiful subject of cavernous sinus surgery for over 35 years, and this journey has been absolute pleasure, an absolute divine pleasure for me. Needless to say that 38 years ago when I started cavernous sinus surgery, cavernous sinus surgery was not very popular as a subject, as an entity. Not many people understood cavernous sinus anatomy, Not many people understood cavernous sinus radiology, and very few people understood cavernous sinus surgery. So I began my journey with my very loved, and very respected, and very wonderful teacher, Dr. Laligam Sekhar. I worked with him in 1989. So that was about 33 years ago when Laligam was a young man. He's still young, but he was about 37, 38 years old at that time and already a very big name in the field of cavernous sinus surgery. So I had an opportunity to work with him, and I give a big credit to his teachings that wherever I am and whatever I am, it is due to his absolute mastery over cavernous sinus and skull base surgery. The other very eminent and the most respected doctor which I want to give credit to my growth is Dr. Manu Kothari. He was one great philosopher. He was an anatomist, basically. But such a great philosopher of science talking about blood pressure, talking about diabetes, talking about various things, and about cavernous sinus, about a huge number of things. So this great philosopher, I worked with him for good 30 years. And in India, we respect our teachers by touching the feet. So for 30 years daily I was sitting by his feet side and got his blessings. So I'm going to talk on cavernous sinus. I have given this lecture several times. Basically, it is a pictorial kind of demonstration. And I want to give some concepts which I have published. Basically these are my concepts, and they're all published concepts over several years, maybe 35 years, and you will see them. Needless to say, anyone who wants to learn and do cavernous sinus surgery has to be master of normal anatomy, and more important, is to have an access to understanding what will happen in the presence of the tumor, and how the anatomy will be displaced and distorted, and how you have to then enter into cavernous sinus. And one has to be an absolute master of anatomy, has to have great experience in surgery, has to have great experience in controlling bleeding from veins, from arteries, has to have absolute dissection techniques. There is no compromise. Because you know, any complication in this area can be quite morbid for the patient as regards the eye movement function, and if carotid is injured, how to handle, what to do, what not to do. Every step in cavernous sinus surgery is critical important, and unless you learn it by experience, you will never be able to do it. So this book I wrote in 1996 on Neurosurgery of Complex Tumors and Vascular Lesions. And if you see the cover page, in 1996, you see the dissection, how we have done the entire petrosectomy has been done, the carotid is displaced, the cavernous sinus, the Gasserian ganglion, how the facial nerve has been mobilized. So this was the kind of picture that we. Actually, not many people were doing this kind of dissection during those days, but this was the cover page. And of course, my work on craniovertebral junction many of you know. I want to begin this journey by giving you some papers which I wrote on philosophy of cavernous sinus. Nobody actually knew, nobody still knows whether cavernous sinus is just an anatomical entity or it does have some role. So I wrote, good 30 years ago, several articles. Cavernous sinus, what is the function of cavernous sinus, what is the role in itself? You see, nerves have a role, optic nerve has a role, but what is the role of cavernous sinus itself in eye movements and eye health, and various other articles which those who will be interested should read it. So what I'm going to do is have several topics I'm going to cover in quick like a procession and give you my thoughts or summarize my thoughts of over 35, 38 years. So this is one philosophical note which I wrote that cavernous sinus is not a vestigial thing, it has definite role in eye movements. And wherever, like in a deer, the deer has to look in front, deer has to look behind when the lion is coming to attack, and it has to look both front and behind at the same time, and the eye movements are very brisk. They are like zzz, come front and back, front and back. And when that kind of movements are there, the cavernous sinus is bigger. On the other hand, a lion has to just look ahead. It is just 30 degree of visual access. Human being has 120 degree of visual access. So it does not have to look too much behind and forward and all those things. He does not bother about what is happening behind. He is just there to catch hold of this deer. So what we speculated is, bigger, larger the function of the eye, the larger is the cavernous sinus. So this was a speculation, and there are several other speculations about the function of cavernous sinus, its role in eye movement, roll in eye protection, and things like that. So eyeball is quite a hydrodynamic system, aqueous humor, vitreous humor, lens are highest degree of perfection of hydrodynamics. Any kind of eyeball pressure, if it is more than normal, it can be bad. If it is less than normal, it can be bad. Lens pressure has to be normal. And needless to say, that this hydrodynamics of eyeball has retrobulbar fat. There is only fluid behind the eye. There are large number of veins which go to the cavernous sinus. So we have speculated that the pressure, the hydrodynamics of eyeball, its considerable extent is regulated by cavernous sinus. So it has a role in the functioning of hydrodynamics of the lens, and other systems in the eyeball. Other thing is, the retinal artery is devoid of any muscularis layer, and it has to be under pressure. Any pressure on the eyeball can just rupture the retinal artery. So the quick drain-off that cavernous sinus provides has a very big role in the function and protection of the retinal artery and other things. So it has got great role in eye movements, and also in vision. And these kind of speculations are mentioned in my article I wish those who will be interested should read. And like circle of Willis, we have said that this is a circle of relief, this cavernous sinus and inter cavernous sinus connections. Like cavernous sinus thrombosis. When there is cavernous sinus thrombosis, there can be proptosis, there can be eye movements disturbance, there can be visual disturbance and things like that, despite the fact that the nerves are normal, the third nerve, fourth nerve, sixth nerve are all normal. So this venous collection, or venous lake has got a great function in eye movements, eye protection. Like if you press your eye like that, if you press your eye like that, this quick drain-off and communication with the other eye will lead to some diplopia for some time and then it will recover. So this is what our speculation was. So the eyes are of different animals and beautiful eyes, and what lies behind the eyes is also equally important. People say brain is important, but I think cavernous sinus is equally important in its role, in its function. So cavernous sinus is located by the side of pituitary gland, by the side of paranasal sinuses. This location is not an anatomical error, it is a functional necessity. Pituitary gland is neither intracranial nor extracranial. This location has very big role to play. So we have said that this paranasal sinuses are like air conditioners of the body. External temperature, whatever, maybe hot or cold, as soon as the air reaches the trachea, the temperature is normalized by these paranasal sinuses. You drink hot, or cold, or whatever, the temperature will be regulated, and in the mouth and in the esophagus, the temperature will be normal. So these are air conditioners and fluid conditioners, and whatever you can call. And this air conditioners give information to the cavernous sinus, carotid artery gives information about body situation in cavernous sinus, and then both of them give information to the pituitary gland, and then the pituitary gland regulates the whole body. So these are just speculations. Whether they are indeed rational or not rational, you have to yourself analyze. Another very fantastic thing that we have worked on is the membranes. And this sentence I got from a Arabic literature and legacy, and where it is written alum al-dimagh, it means the meninges are the mother of brain. So this meninges are the mother of brain. Dura mater, mater means mother. So the origin was from this terminology. And this indeed, is a very important thing. When meninges are the mother, meninges come first, brain comes second. Dura comes first, bones come much later. So these are very important to understand, that dura is strong, meninges are strong, dura is a compact, keeps the brain compact. There is no question of, it does not end in the foramen, it just continues along with all the nerves. No nerve pierces the dura. Dura goes along with the nerves. So there is no question of having any kind of communication. That is why you see this various kinds of infections can happen, COVID can happen, whatever can happen, but brain is a protected entity because of the meninges, and these are very important, there is no question about it. So what we said was mandibular nerve comes first. It does not pass through foramen ovale. On the other hand, foramen ovale as an evolution is formed around the mandibular nerve. Very important sentence to understand, dura is durable. Another beautiful sentence I'm going to give you is that the brain is nothing but sunken skin. You should analyze this sentence in greater depth and you will realize the beauty of this sentence. And then we have written several articles since, for about 30 years, on cavernous sinus. And these papers, some of them I think, if you are interested, you can go through some of these papers. Of course, I'm going to summarize the content of these papers now in front of you. So this was one paper, cavernous sinus surgery has developed because of, of course, understanding of anatomy, of course, but also, understanding of radiology. This kind of image was not possible till MRI came into picture. CT scan was not able to show you this kind of beautiful artery right in the middle of the tumor, and this artery being displaced by the tumor. This information is given by MRI. So this article of mine in 1998 I think was quite a beautiful paper, and we described that on the basis of arterial size, on the basis of arterial displacement, you can understand this tumor is a meningioma, this tumor is a pituitary tumor, or this tumor is a paranasal sinus tumor, this is a nasopharyngeal angio fibroma, this is this tumor. So on the basis of nature of arterial displacement, on the nature of the arterial caliber, you can make a diagnosis of what tumor is that, and then accordingly, you prepare your surgery. And it is so important to know what you are going to deal with during the surgery to prepare your surgery appropriately. Because every tumor has a different mindset for the surgeon, every tumor should be considered in a different. You just cannot talk about one approach and I will do all these tumors by one approach, or I will do everything biosimilar. Every tumor has a different strategy, every tumor has a different way to hold the instruments, different way of dissection, different way of breaking the tumor. It is so important to understand what tumor you are going to operate. So these are some initial papers on how the meningeal architecture of cavernous sinus and surgery. So these are very old papers. During that time of course, cavernous sinus surgery was born, but it was just in a very preliminary stage. So in '89, I worked with Dr. Sekhar, but then when I came back into my public hospital where I got an opportunity to operate, operate, and that is what I think was the key to my whatever success I have got. So I was blessed with a huge number of cases, and that is my power. And in 1993, you can imagine, this tumor to remove 30 years ago was a difficult challenge. You see the instruments were not all that, and microscope may have been a little bit preliminary. But you see 1993, this was the surgical thing that I did. And this patient was, you see this patient is still living. She was blind before operation, but she's still blind, but she's alive. She refuses any kind of further imaging. But this was the imaging, and you can see the petrosectomy done, and wide kind of exposure that must have been done at that time. This was another tumor I removed in 1995. This was a meningioma. This was another tumor where I had left some tumor behind, and at that time there was no question of gamma knife. There was gamma knife in India at that time, but we were not very happy with giving gamma knife, and this patient was operated quite beautifully, as you can see. This was another patient I did in 1997. You see the radicality of resection. And by these, with complications, with understanding, operating repeatedly, and again and again and again with huge number of cases, huge complexity of cases, that is what I think helped me in understanding these tumors and that understanding, I want to relate it to you. So this was another tumor. Somebody had done temporal lobectomy but not touched the tumor. Then it was a very straightforward exposure for me, and I removed it in quick time. See, it is very important to understand the consistency of the tumor, vascularity of the tumor. I have a feeling that radicality is one thing, but your philosophy about what this tumor is, how it should be removed, how much it should be removed, and most important is, if the patient is damaged by your surgery, it is a wrong surgery. If you create a visual deficit of eye movement, it happens, it happens even in our life of neurosurgeon. You can do a glauma, you can harm the person. But the best surgery is when you have not harmed the person, you have given a good opportunity for him to live, and you have done a good job of resection. Of course, biopsy is no longer necessity. Biopsy is redundant, it is not an operation. All these tumors, you know before operation what tumor you are going to operate and how you are going. What tumor is a very straightforward thing. So this was another complex case I did in 1997. There was one tumor behind the eyeball, one tumor in the cavernous sinus, and this turned out to be a schwannoma and this turned out to be hemangiopericytoma. And this patient was living. Till very recently I saw him without any issue. You see, it means you could have an opportunity to give life to the person. You can give a wonderful symptom-free life. So this surgery is indeed, has developed and developed to an extent that we are all now talking about it all the time. Extradural approach to tumors involving cavernous sinus. Extradural approach to vascular lesions, of course, Dr. had described, and he did a lot of cases. But this was the first article in the literature which talked about extradural approach to tumors involving cavernous sinus, and I will like to show you that. This was a hemangioma of cavernous sinus. I did it in 1991. And cavernous sinus hemangiomas are the most vascular tumors, are the most benign tumors, and the most difficult tumors to be removed. And the issues of six nerve, issue of cranial nerve deficit, issue of arterial damage and high vascularity. And this patient I did in 1991, I don't know if there was any case which was reported of cavernous hemangioma complete resection before 1991. This I feel was the first case. I'm not sure though. The beauty of cavernous hemangioma is, it is now mater dural. Mater dura cavernous sinus is an extradural entity or interdural entity, the discussion will go on. Cavernous sinus hemangioma occupies the confines of the cavernous sinus. It is the primary intra-cavernous sinus tumor. It goes towards the orbit, towards the Meckel's cave, through the intercavernous sinus it goes like this. So this kind of pattern of extension, completely intracavernous. The fifth nerve, the third nerve are all displaced on the dome of the tumor, on the outer dome. They are not inside the tumor. The carotid artery is encased by the tumor. And the sixth nerve is on the inferior dome of the tumor, inferior. So this is my understanding of cavernous hemangiomas, and it is a highly vascular tumor, as we all know. So no matter how big this tumor becomes, the pattern remains the same, the orbit, Meckel's cave. Lateral dural wall remains intact, always. The cranial nerves are displaced laterally. The sixth nerve is displaced on the inferior dome of the tumor. Carotid artery is displaced on the inferior dome of the tumor like this. So this has a well-defined intra cavern, and this has to be understood. If you understand the anatomical concepts of this tumor, you can possibly remove this difficult benign tumor. Many of these tumors come by headache and some visual deficit. More than visual deficit, eye movement disturbance, third nerve, sixth nerve. So this tumor, cavernous sinus is an extradural entity. We described for the first time in the literature, cavernous hemangioma, extradural approach to cavernous hemangioma. And this was my paper. For the first time we described extradural. No question about it, that these benign tumors have to be removed extradurally. You come transcranial, you come through the dura, you can have various other issues. Other thing is, if you do not understand this tumor and you take a chance of coming through endoscope and through the nose, you are done with. This tumor will bleed furiously on front of your eyes, and I am not sure if you will be able to handle the bleeding if you do not understand this tumor and use endoscope and come. So this is another large tumor. You see the pattern is similar, anatomical extensions are similar. And if you are able to remove, you are able to cure the person. And this is the only way, removal. Radiation some people are giving, and now some people are seeing good results of radiation. But in general, if you want to cure the headache of this, you have to remove it radically by surgery. So I reported my series of 45 cases, which I believe is the largest personal experience on this hemangiomas, and we have got several beautiful, beautiful cases. So this is one case I want to show quickly. Now here, you see the thing has been exposed extradurally and I am splitting the nerves. Now I'm splitting the Gasserian ganglion. The splitting of the Gasserian ganglion and to reach the tumor medial to the Gasserian ganglion, there is another layer of dura. You see, the other thing that you have to notice is that from here, from this point, it is not an edited tape. It bleeds. It bleeds and it bleeds. But there is no point in going on coagulating. If you go on coagulating, you may not be able to handle it. The other thing is, you have to work over the carotid artery. The sixth nerve is lateral to the carotid artery, and on the inferior I specified the sixth nerve, separate the sixth nerve, and then you see the inferior lateral trunk of the carotid artery, which is the main feeder to these cavernous hemangioma. Sometimes other arteries like McConnell's capsular and some middle meningeal also can be a feeder. Now you see for the first time I brought coagulation in my picture. And I have to tell you one thing, learn the art of breaking the tumor, not by coagulation. But demolishing the tumor is such an important art in neurosurgery. If you just go on playing with coagulation and playing with coagulation without having, you can have a very big situation. So my feeling is, cavernous sinus surgery, most of the cavernous sinus artery, and then I have worked in that situation. Can you go further, Luke? And the bleeding, you see bleeding will stop, and bleeding is not such an issue. Hardly any coagulation is required in even the most vascular tumor of neurosurgery. Next slide. And this is preoperative and postoperative. And this is another tumor which I had a video, but you see video takes quite a bit of time. This is the tumor. Patient came with third nerve weakness and headache, and severe headache. And this is the patient. You can see the face, and you can see the smiling face. You can see the third nerve, and you can see the eye movements after about two or three months of surgery. So there is a possibility of returning back not only the eye movements, but headache and the smile, and cure. That cavernous hemangiomas are rare tumors but they are beautiful tumors to operate. And cavernous sinus anatomy, if you want to see in a panoramic fashion, this is one tumor. Carotid artery is encased. There is an aneurysm in this case. This was a rare case, so we clipped the aneurysm about 25 years ago and removed the large cavernous hemangioma. This is another tumor which you have. Now I want to go rapidly to pituitary tumors, and I want to discuss the dural anatomy of pituitary tumors, which is absolutely important. If you understand the dural anatomy of pituitary tumors, you can operate these tumors much better. And I have written several articles on this subject. So tumors can become large and become huge. And even if they become huge like this, they have specific pattern of extension. There is a method in this madness of this tumor. If you know exactly how the tumors will spread, you make a preoperative diagnosis. No matter how big these tumors become, they are benign in nature and they have a specific pattern of extension, and that pattern I want to talk to you about. For the first time in the literature we said that the diaphragm sellae is elevated on the dome of the tumor. This sentence was never written before we said this. The question earlier was that diaphragm sellae is buried is in the whole of the diaphragm, the rest of the tumor comes, and this part of the tumor is in subarachnoid location. This was the concept. About 25 years ago we said it is the dura, the diaphragm is elevated on the dome of the tumor, and this tumor is completely subdural or interdural in nature. Very important. Because if you know that the dura is elevated, you can come from the nose. Many of these tumors during that time were done transcranially. But I think this description has changed the mindset of neurosurgeons, whether you use endoscope or whether you use microscope. You have to just take this incision, then break into the tumor, learn the art of demolishing the tumor. And in about 15, 20 minutes, the whole diaphragm should come into your picture. If you go on coagulating, you will never be able to remove pituitary tumors. So this diaphragm cellae elevation, and this interdural location of the tumor is absolutely important. You come from here, just remove the anterior wall, break into the tumor. Many of these tumors are soft, they are vascular. The diaphragm will pump into picture eventually. Even this nubbin is within the dura. So this concept has got great relevance in surgery. This nub in here, this is intracranial all right, but this is interdural. The dura covers, dura covers. This concept, I think, had revolutionary impact in the understanding and surgery of pituitary tumor. This is another tumor you see. If you do not know that there is dura here, to remove by any kind of group, whether you use any endoscope or transcranial group, unless you know that the dura is going to protect you, you might find great difficulty in operating. And in pituitary tumors, if you don't do radical resection, you do small resection, you can have a problem of bleeding and there can be postoperative hemorrhage. Grade two we said that when the tumor enters into cavernous sinus. Which tumors enter into cavernous sinus? Which tumor, that is a controversial issue. Now even the lateral dural wall of the cavernous sinus is displaced, but never transgressed by the tumor. So there is diaphragm here, there is dura of the lateral wall of cavernous sinus. There is both carotid arteries encased. It means both cavernous sinuses are involved. There is lateral dural wall, there is roof of the diaphragm, there is lateral dural wall. This is completely within the dura. So dura is there all around this tumor. And if you want to remove cavernous sinus, you have to understand where will be the nerves displaced, how will be the nerve displaced, and how you have to resect these tumors. This is another chapter of neuro surgery. Now carefully see this slide. The diaphragm is elevated, the lateral wall is elevated but not transgressed. Dura is mother. They are benign tumors. They don't have the power to transgress the dura or the mother. Dura can be stretched, dura can be stretched, but it cannot be transgressed. So this understanding, I think, has great relevance which was not there earlier. Now grade three is when the dural roof of the cavernous sinus is elevated. This kind of elevation, there is dura covering the tumor. So when the dural roof of cavernous sinus, which is quite a common kind of clinical entity, we labeled it as grade three. This part of the tumor is under the dura, was never discussed earlier in the literature. And it is quite a common thing. This is roof of cavernous sinus, this is diaphragm cellae. This is, you see how clearly it is seen, the elevation of roof of cavernous sinus diaphragm cellae. This is elevation of roof of cavernous sinus diaphragm cellae, elevation of roof of cavernous sinus. So this kind of tumor is not haphazard kind of extension. It has got a defined pattern. And when it goes in the subarachnoid space and encases the arteries of circle of Willis, I call it aggressive tumor. People who don't respect their mother are aggressive people. These are aggressive tumor. And what type of surgery has to be done is another chapter. You see the outcome, whether you want to do radical resection. Radical resection, I have to tell you, is wrought with danger of huge problems. So this is my grading scale. Grade one is when the diaphragm is elevated and the tumor does not enter into cavernous sinus. Grade two is when diaphragm is elevated, it enters into cavernous sinus. This is grade two. Grade three is when the dura of the roof of cavernous sinus is elevated. And grade four is when the arteries of circle of Willis are encased by the tumor. And this classification, if you read my articles, you will see how the surgery differs, and how the prognosis and outcome differs, and what are the indications for radiation treatment in these cases. So this was another. I have a feeling these had great implications in the surgery of pituitary tumors, and I have no doubt that this concept has revolutionized pituitary tumor surgery. So you have to just remove the anterior wall of the tumor and break into the tumor, break into the tumor. You all know that these are soft tumors. Since many of them are cystic tumors you don't need to coagulate. I have done more than 5,000 pituitary tumors. I don't think I've ever used quarterly or bipolar within the confines of the tumor. That is an unnecessary tool. You break the tumor, break the tumor first, break the legs, go side, and then the whole bulk will bow, the head will come down, bowing in front of you. So this is what we had said, that the pregnancies should come from the vaginal route. The uterus is the strongest muscle of the body. Any cesarean section is an unnecessary procedure. Similarly, we said that the diaphragm is a strong component of the dura. It has great power to push the tumor down. You just remove the belly and break into the tumor. You see necrotic cystic area, and within few minutes the tumor will be down. And there is no need to even repair the base when the whole diaphragm is herniating down into the field. And the patient, these are non-functioning tumors, the vision will improve in the evening of operation. On the other hand, if you have removed partially and incompletely, and there is no role for transcranial surgery in this. Believe me, my dear friends, these kind of tumors were all done transcranial 20, 25 years ago, and now nobody will do transcranial. Some people still like to do transcranial. This sub-frontal extension, this was a very classical indication for transcranial approach. You believe me, I removed this tumor in 15 minutes, just remove this. And how to get this tumor out is an issue, and you have to learn how to handle the dura, how to handle the diaphragm, how to pull the diaphragm down into picture and remove these tumors. This tumor I removed 22 years ago. Can you believe this tumor? And that time, this tumor, nobody would've dared to remove this tumor from the nose. For your information, I don't use endoscope, I use microscope, and I find there is no question, microscope is such a fantastic tool to operate. No interference by any other hand, no violation of anatomy, no coagulation of nose and nasal mucosa and other things. And this tumor you see, 22 years ago I removed beautifully, this tumor. Another tumor, 23 years ago I removed this. Can you believe this tumor? I removed it from here, and this is immediate postoperative scan. It is like doing, to come here and I am not sure whether I removed this tumor, planum sphenoidale and tuberculum sella bone. Normally, my strategy is just remove anterior, break into the tumor, break into the tumor. If the patient is having severe headache, the tumor will pulsate into your picture. Use Valsalva maneuvers and other maneuvers. Tumors in the cavernous sinus is another story, another beauty of how to remove tumor in the cavernous sinus, when to remove, when not to remove. And this is, you have to be philosophical in your understanding. You just cannot be technical in neurosurgery. You see, this is elevation of roof of cavernous sinus. I had removed this tumor here, but I had not removed this tumor in the. So normally in residual pituitary tumors, you don't need to give radiation treatment. But when the roof of cavernous sinus tumor remains, you need to give radiation treatment. So this was another tumor I did several years ago and removed this tumor from the roof of cavernous sinus from the nose. It is possible, you have to understand the anatomy, how the carotid is displaced. Majority of these tumors are soft. You don't have to use coagulation and sharp instruments in the cavernous sinus. If you do that, you might have land into problem. You'll displace the structure and use your soft suction to remove these tumors, and that is how you can remove. And when the tumor encase the circle of Willis, it is another chapter. Many of these tumors are hormonally active and they need another kind of treatment. Now I want to talk to you about my work on trigeminal neurinoma. And this was the paper I wrote about 20 years ago, 73 cases. Now experience is more than 300 cases of trigeminal neurinoma, which I believe is the largest experience in the world on this subject. 20 years ago, I wrote this article where I mentioned for the first time in the literature that trigeminal neurinomas arise in the region of Gasserian ganglion in the region of Meckel's cave. That was one thing. Second thing I mention, for the first time in the literature that you can remove this tumors and improve the trigeminal sensation. No one had earlier mentioned that trigeminal sensations can improve after surgery. Third thing we mentioned was about the dural anatomy. We said that cavernous sinus portion is completely interdural in location. For the first time in the history of neurosurgery, we used this interdural location to use. So these tumors are within the confines of the dura. You break the tumor using instrument without coagulation, and you can identify the fibers of the fifth nerve and save them. Many a times in this article we had said that this part of the tumor. I think I'm not using the. This part of the tumor is subarachnoid in location. But this part of the tumor is actually not subarachnoid, it may be interdural in location on several location. So this part of the tumor we had said that this is subarachnoid, but many a times, particularly multi-compartmental tumors can be subdural, or interdural in location. So these are the things that we discuss in this article. And this beautiful article in 1995, you see the title, "Interdural approach." And what we did was, we did not do any craniotomy. We just opened the Meckel's cave and worked within the dura to remove this tumor. In 1995, I am showing you some pictures of my 1995 article where we showed this was one tumor. So you have to make radiological diagnosis, you have to make clinical diagnosis. So this tumor was operated by just opening and widening the Meckel's cave and removing this tumor. 1994 I removed this tumor. You see here, this tumor is in the posterior fossa, this tumor is in the interdural location, and I removed by just this small craniotomy here and worked within the dura, worked within the dura and I removed the whole tumor without any craniotomy in 1994. I think that during that time, nobody actually understood trigeminal neurinomas to that level. But this dural anatomy was quite beautiful. In that same paper I removed this tumor without any craniotomy by understanding the anatomy, by understanding the dural anatomy. These tumors are interdural, they displace the carotid artery medially. So I will say that any approach from the nose, or I use endoscope from the nose, it is not a good operation to use endoscope for trigeminal neurinomas. The carotid is displaced here. You work from here, open the dura, work within the dura. There is dural cover around the entire tumor. Demolish the tumor, demolish the tumor. Identify the cranial nerve. Coming from medial just is not a good option in my view, although many people do operate. I want to do transnasal and I want to do this nasal. But carotid is medial. So you come lateral, open the dura, extradural, interdural, and work within the. So this tumor I had removed without any craniotomy, but now of course, I don't. This was another paper in the same paper which I have mentioned. So this tumors, this posterior fossa component we had said is subarachnoid like acoustic. But now we are saying, in several of these multi-compartmental tumor, it can be also interdural. So in 1991 we did this case. During that time, trigeminal neurinoma single stage approach was hardly done. It was done in two stages. As you can see, I had also done in two stages. First I removed the middle fossa and then I removed the posterior fossa in 1991. Here is 1992. I first removed this posterior fossa and then I removed this cavernous sinus tumor, and this was in 1992. But then of course, our understanding of dural anatomy and our understanding of skull base anatomy. So this article of mine talks about temporal craniotomy in addition to mastoidectomy. So first time in the literature, I think, mastoidectomy was incorporated in temporal craniotomy. So we did route of zygoma resection, roof of condyle, roof of external ear canal, and mastoidectomy to get a basal exposure for largest tumors. Of course, as I have said, that we used even infra temporal fossa approach, but this kind of approach we used for largest tumors. And I think this was, in my growth of skull base, this was one of the milestones. So then we started doing splitting of the temporalis muscle and just doing this smallish craniotomy for large tumors. And the other thing is, you see here, temporalis muscle is rotated anteriorly, there is basal craniotomy. So this kind of thing that we did, even temporalis muscle was rotated downwards and zygomatic was a very common thing at that time. Orbital zygomatic, frontal orbital zygomatic osteotomy was also very common at that time. But we avoided all those things and did this kind of maneuvers. So this huge, as I mentioned, we have got experience of over 300 cases over several years, and there are some beautiful, and I have given several presentation for last 30 years on trigeminal neurinoma, come interdural. For these large tumors which are going posterior fossa, I like to come intradural. For smallish tumors which are located in the cavernous sinus, I come extradural and then take an incision, and then demolish the tumor. These tumors are soft necrotic, hardly any vascularity. And I have to tell you that these tumors should not be removed in more than 45 minutes. If you are going on for 10 hours in these tumors, you have to learn how to break the tumor. The coagulation within the confines and outside the confines is not such a. Very minimum coagulation is required and you can, if you are minimizing your coagulation, you can actually save the cranial nerves much better. So we have got several, several examples of these kind of dumbbells of various shapes and sizes. Basically, this part of the tumor is intradural. In several of these cases, even this part is also interdural work. Open the dura, demolish the tumor, break the tumor, break the tumor, break the tumor, and then you will find the carotid artery is medial to the dura. You don't have to expose the carotid artery. If you say I have carotid control here, carotid control there, at that is not necessary, and absolutely not necessary. Even when there is a small nubbin like you see here, this is also like pituitary tumor I showed you. This is also interdural in location. Come from here, open the dura, demolish the tumor with suction and with soft instruments without any coagulation, quickly, quickly. And then you find the cranial nerve and then you save the cranial. You have to save if you damage the cranial nerves in this situation. This was the tumor where there was, you see, there is no need to do anterior clinoidectomy or petrosectomy. This tumor by itself is doing all those things. If you say I do anterior clinoid resection, if you say I do petrosectomy, these maneuvers are not necessary. You come from here, break into the tumor, work within the dura, demolish the tumor, demolish the tumor without much coagulation, and then you remove this tumor. Another beautiful thing we mentioned was, when the tumor is extracranial, even that part of the tumor is covered by dura, and this part is also covered by the dura, this extracranial part is covered by the dura. So this is along the V1, this is along the V2 division, this is along the V3 division. And all these parts are critical. So you work within the dura, work within the dura, and you can avoid working with the extracranial carotid, other arteries and nerves in this region. So we said that these tumors should be operated in a reverse skull base approach. You don't have to come from infratemporal fossa, do a smallish craniotomy, retract the dura, and then identify the dura and then work downwards rather than going from below up. So this is, I had labeled it as reverse skull base approach. Another beautiful thing that we realized, that even when the tumor recurs, it is within the dura. Recurrence is also interdural in nature. And also, there are special features in trigeminal neurinoma like cystic tumors, fluid level within the tumor where the recurrence rates are higher. So we have discussed about the how to operate on recurrence of trigeminal neurinoma. Now I want to show you another beautiful skull base tumor. This is a third nerve neurinoma. Definite clinical symptom, presence of third nerve deficit is an indicator of third nerve neurinoma. So how you operate on the third nerve neurinoma is a difficult job. We said in our article that this tumor is entirely within the confines of the dura. This was my article in Acta Neurochirurgica where we said that third nerve neurinomas arise within the oculomotor system. And like I said about trigeminal neurinoma, it arises in the Meckel's cave. This tumor arises in the oculomotor system, and then it grows and covers the dura completely. So you come inside and open a smallish part of the dura, and then break into the tumor, break into the tumor, and there is a possibility of retaining the third nerve function after surgery, which has never been reported in the literature. So understanding of the dura is so critical. This is another third nerve neurinoma. You see how the dura is circumferentially covering the tumor. And this understanding is an absolute important when you are going to do a third nerve neurinoma. Sixth nerve neurinoma is a different entity. We are still working on how the dural relationship of six nerve, but it is encasing the carotid artery, schwannoma. So we are not yet sure as to how the dura is related to sixth nerve neurinomas. Another skull base tumor is seven nerve neurinomas. Now the beauty is, we have said that seven nerve neurinoma arise from the region of the geniculate ganglion. And when it becomes large, it is covered entirely by dura. And this understanding is so important, interdural. This relationship has never been discussed in the literature. So you come from here, open the dura, and then demolish the tumor and save the area of the seven nerve, although we have not been able to ever save the seven nerve function or improve the seven nerve function. But there is a possibility of improving if you do not violate this dura during surgery, and I think it is a very critical step of surgery. Another beautiful thing about lower cranial nerve schwannoma. Lower cranial nerve schwannomas are difficult skull base tumor. Not all, but a large number of these tumors respect the dura and they are interdural. This is published in World Neurosurgery, where we have said, for the first time in the literature, that you work within the dura, don't go outside the dura in all the three components of the tumor, and you can actually improve the function of the lower cranial nerve. So we have, you see here, if you read this article, we have said that there is a distinct possibility of improving the function of the lower cranial nerve on a consistent basis. So this tumor is entirely confined within the dura. So you have to know how to enter from here, or you have to enter from here, or you have to enter from here. But wherever you enter, you have to expose the tumor dura and not go outside the dura. You see this tumor is completely within the dura. And this understanding of the dura, I have no question or no hesitation to say, is a complete radical revolution in this. You see here, there is some dura kind of things preserved, but the whole tumor has been removed by working interdural. More technical details I mention in the paper. I wish you please read this article. Intracranial part of the tumor is also covered distinctly by the dura, and that dural anatomy, how you protect the dura, all the other cranial nerves are displaced around them. Another fantastic tumor I'm going to talk about is C2 neurinomas. C2 neurinoma, I had published some years ago my series of 60 cases of C2 neurinoma. In that series we had said that there are three components of these tumors. One is A, B, and C. This is intraspinal part, and this is interdural part of the tumor. This is what I had said. And then you can actually come from here, don't have to open the lamina, you don't have to open the canal. C2 is the only ganglion which is exposed. C2 ganglion is outside the canal, behind the C1, C2 articulation. Make a transverse cut on the dura and remove this tumor. And I have demonstrated several times in various workshops that these tumors can be removed in 20 minutes or 15 minutes if you know that these tumors are within the dura, the vertebral artery is displaced, you don't have to control the vertebral artery and you can do a very quick job. In 2018, we changed our perspective to these tumors and we said that even this part of the tumor is interdural, within the confines of the dura, interdural. So we make a cut here, break the tumor, break the tumor, break the tumor, and do not transgress the dura, respect the dura. Tumors also respect the dura, you also respect the membrane, and that is how you can remove these tumors in very quick manner and in a very safe manner. Quickness and fast, I did them in 10 minutes or 15, that is not the issue. You have to remove it philosophically and you have to remove it radically. The patient has to improve. You have to remove it philosophically, that is so important. So this is C2 ganglion, which is behind the C1-C2 articulation. This is the only ganglion which is outside the canal. So tumors here are resembling very much like trigeminal neurinoma. So in our article we have said that light trigeminal neurinoma can be interdural here, interdural here, and sometimes interdural here. Similarly, this tumor is interdural here, interdural here, and interdural here. Take a transverse incision. C2 nerve route, even if they're damaged it does not really matter. And you remove this tumor, and you create a beautiful clinical outcome. So this is my strategy for C2 neurinoma. Strategy for trigeminal neurinoma, absolutely similar. This is C2 neurinoma you see, and this is trigeminal neurinoma. Similar anatomy, similar relationship here. Veritable artery is related here, carotid artery is related, similar consistency, little bit stronger, little bit . Trigeminal neurinomas can also be formed. Whenever they are soft and cystic they are more aggressive in nature. You see this is C2 neurinoma, this is trigeminal neurinoma. Now another tumor, very favorite tumor of skull base surgeons. And this was one of my favorite articles, which I wrote in 1995 or 1996, like chordomas arise from the bones. They displace the soft tissue. They do not have power to displace or violate the dura. They displace the carotid artery anteriorly. They displace the cavernous sinus superiorly. This anatomy is absolutely important if you want to remove a chordoma. If you don't have this understanding, I have a feeling that you may not be able to remove chordomas. So you see here, the carotid artery is displaced anteriorly by the tumor. The dura is intact. Very, very rarely I have to tell you that the dura will be violated. Mater dura. These tumors do not have the power to violate the mater dura. Cavernous sinus is displaced superiorly. Another beautiful anatomical piece that we recently wrote is about the sixth nerve. Nobody knows about the sixth nerve, how it is displaced. Now recently we have said that the sixth nerve is displaced along the cranial nerves. There is a big distance between the sixth nerve and the carotid artery, and this distance should be exploited during surgery. And I will tell you how. So carotid artery is displaced anteriorly by chordomas and hondrosarcomas. Cavernous sinus is displaced superiorly. Dura is displaced posteriorly. So we talked about middle fossa, sub-Gasserian ganglion approach to carotid artery. So in 1996, I wrote about these anatomical beauties about chordomas and how the internal carotid artery is displaced and the relationship. I think these are very fantastic paper 30 years ago. So this tumor destroys the bone, this tumor displaces the soft tissue, and this middle fossa sub-Gasserian ganglion approach. So you come from lateral, you come from lateral, open the dura, work within the tumor, work within the tumor, carotid arteries anterior, and you have the whole structure in front of you. Of course, many of these tumors, which are predominantly in the nasal pharynx, can be removed by transnasal route. But I have no hesitation to say that middle fossa route for clival chordoma is a wonderful approach on several location. It's a controlled approach. So this tumor, you see carotid artery's anterior. This is dura here. So on the basis of understanding of the dural anatomy, you can make the diagnosis of a chordoma. And on the basis of that diagnosis you can work and remove this tumor in a very quick time. These are soft tumors. These are like jelly-like tumor, whether you remove from whatever jelly. And once you remove, the whole anatomy comes in front of you in a panoramic fashion and you are becoming so happy about it, how much bone to remove, how much clivus has to be removed. These are different issues which have to be understood and clearly recognized, whether you have to remove more of cliver, so much of cliver, so much of bone. But these tumors are an enigma in neurosurgery. You remove it radically when it recurs. Nobody has control over them. So these tumors are histologically benign, behaviorally aggressive tumors. This is another chordoma. And you know, whether I want to remove from the nose, whether endoscope is necessary or whether endoscope is useful, this tumor is coming too much lateral. I have a feeling that there is no question in my mind that this. Can you run the video? Yeah. You see, I'm exposing from lateral extradural approach, and the whole anatomy is right in front of me. This is carotid artery here. Carotid artery is under my control. Six nerve, which I have talked about, which is displaced along the fifth cranial nerve, can be exposed. But of course, sixth nerve can be damaged during these operation. But that is the purpose of operation. You see how much control anatomy is there. If there is some carotid artery issue, anything, I think transcranial approach has got great relevance. Next slide, Luke. More recently on the basis of dural anatomy, on the basis of anatomy of the sixth cranial nerve, we discussed the supracerebellar approach to clival chordoma, which was published in World Neurosurgery. And my feeling is, there are some occasions like this one, whether you want to come from here, whether you want to come from the nose. So we use this approach. You see, this approach, supracerebellar approach, if you come from this approach, you get to the dura, work within the dura. These are soft jelly-like tumor. Then you remove like this in this direction and you can have. More important in this is that you identify the sixth nerve early in the operation and save the sixth nerve, which goes like that on the dome of the tumor away from the, and the carotid artery's anterior. So these things make this approach a possibility. So we talk about supracerebellar approach for clival chordoma, in select cases of course. You will not like to use this approach on a regular basis. So this tumor was going into the clivus. We had a doubt about clival chordoma, but of course it was not such and we did it transcranial supracerebellar and beautifully resected this tumor. This was another tumor which we resected supracerebellar and removed it beautifully. Now, nasopharyngeal tumors. You see nasopharyngeal tumors, nasopharyngeal angiofibromas in particular, they are extracranial and extradural in nature. So we had discussed, nasopharyngeal angiofibromas are another vascular tumors and can be dangerous by vascularity. How is the cavernous sinus relation? So we had talked about, you see the cavernous sinus is displaced, so you can develop a very beautiful plane of dissection by doing transnasal approach. So transnasal approach is a beautiful approach for nasopharyngeal angiofibromas. But we have discussed in 1992, transcranial approach. For the first time we talked about this transcranial, and this was my pictures in my paper. But now of course, I do not recommend transcranial approach. Transnasal approach is beautiful. Epidermoid tumors can be in various layers of cavernous sinus. Aspergillomas can be there. Tuberculomas can be there. So there are various, various tumors. Now, briefly I will talk about meningiomas. Meningiomas are tumors from the mater. They are meningeal tumors. They can be dangerous, they can be on both sides of the dura. And we have to understand, you cannot just rational I want to remove aggressively, I want to remove totally, and all those things. That that is not such a great. You have to understand how the meningioma. So to talk about some meningioma. Like this is a convexity meningioma. This is not going in the superior sagittal sinus. This is going little bit in the superior sagittal sinus. So this tumor is little bit more aggressive than this tumor, because it is going in the superior sagittal sinus. This tumor is not only involving the superior sagittal sinus, it is involving the cranial. So this is inherently more aggressive form of meningioma. This tumor is going into the paranasal sinuses here. This is almost like a malignant tumor. This part of this tumor is, this is a meningioma, but it is more aggressive form of meningioma. This is another meningioma which is in the paranasal sinus. When the tumor involves outside the confines of the skull, they are inherently more aggressive tumor. We have to understand this. Similarly, in cavernous sinus, you see, this is on both sides of the dura. This is a peculiarity of some cavernous meningioma, not all. So when it is in the cavernous sinus, it is inherently more aggressive. We have to understand this. This meningioma completely within the cavernous sinus is inherently more aggressive. We have to remove aggressively all tumors, but we have to understand before operation that we are dealing with an aggressive problem. So this tumor is like a convexity meningioma. It is not involving the cavernous sinus. This tumor is involving the cavernous sinus. It is inherently more aggressive meningioma. This tumor is involving the paranasal sinuses. It is like a malignancy, or an aggressive tumor. So this tumor you see completely within the cavernous sinus I operated in 1995. The recurrence is higher within tumors which are basically in the cavernous sinus. This was another intra cavernous meningioma, which is rare tumor, vascular tumor. I removed it, but this tumor also recurred. Now this tumor, which goes in the paranasal sinus, we have to understand before operation that we are dealing with a very aggressive tumor at par with the malignant tumor. Now you see this tumor getting vascularity from the outer wall of the dura. This is not inside the cavernous sinus. This is a benign meningioma and has to be removed radically. And the results are as good as a benign tumor. This tumor is getting fetus from the posterior wall of the cavernous sinus, and there is nothing in the cavernous sinus. You remove it radically, beautifully, and it is like you have cured the person. Of course, that would cured. This is also giving vascularity, is from the posterior aspect of the cavernous sinus. You remove this tumor, and these are very benign tumors. Now this tumor is also from the lateral wall and this has been removed. This is a rather straightforward tumor. So earlier in my history of my work, I was quite aggressive in my exposure, petrous carotid displacement, facial nerve displacement, work very commonly done in my surgical domain. But now, of course, as I have grown in my subject, as I have got more and more experience with tumors, my exposures have become limited. So this was the first time that we described middle fossa, extended middle fossa approach where we dis cut the GSPN and displaced the labyrinthine and tympanic segment of the facial nerve, and expanded the Kawase's triangle and had this kind of corridor for various tumors, including chordomas, and some meningiomas. But now we have recently, which is a very popular, for the first time in the literature, this supracerebellar word we use for petroclival meningioma. Of course, Professor Sami has done posterior fossa approach for this. But this term supracerebellar was used by me for the first time in the literature. And I think this is a beautiful approach from many of these petroclival meningiomas, this supracerebellar route. Sitting position is important for many of these cases. So this was done by supracerebellar. Now we have got a very huge series where we have done supracerebellar. Even if some tumor is remaining here, we can handle that by observation. You see, when to use radiation is another chapter. I don't want to confuse you with those kind of things. This was another tumor by supracerebellar route. Also supracerebellar route, you can have a direction like this and remove it. Now, how to remove? As I have mentioned, that many of these tumors sitting position is a very worthwhile. So these tumors sometimes are soft. Many of these tumors which go like that are soft and aggressive tumor, and you have to remove. This is a beautiful approach. This tumor is also supracerebellar approach. And you can have very beautiful anatomical description. Just see some terminal part of the operation. I'm showing all the cranial nerves in that kind of a complex tumor. By supracerebellar, they see this direction hardly, and in 10 minutes I expose the tumor and start working. Consistency of the tumor will be a matter. And if it is soft tumor, why you want to work for hours and hours with all these kind petrosectomy and all? So many of my tumors I removed with supracerebellar. Next slide, please. This the another tumor. You see how carry out this and that. You don't have to remove the whole and all those things. You can do with a very conservative. This is the same patient. I just want to quickly show you the end of the tumor resection. And you see my exposure from the supracerebellar. The consistency of the tumor will matter, and vascularity will matter, and the relationship will matter. How much you can remove will depend on how much this firmness of the tumor, and all those things will certainly matter. Next slide. This is another one similar. I wanted to show you how the anatomy can be seen. Okay, next slide, Luke. This is another one. Just show the video quickly. This is just the terminal part showing you how by supracerebellar you can see the basilar artery and vertebral artery from this after tumor resection. So it is not, you know, various issues will matter. Okay, next slide, go Luke. Tuberculum sellae meningioma, I published my series in 2002. Now my experience is beyond 300, which is also I think the largest anterior glenoid olfactory group meningioma. This is also my personal series, which is quite a large series. I quickly want to give a last lesson, last chapter of my discussion on foramen magnum tumors. We were all used to doing extreme lateral and mobilization of vertebral artery and things like that. Several years ago, I talked about midline approach, midline suboccipital approach. Get this corridor, learn the art of breaking the tumor within the cranial nerves, within the blood vessels, and you can do a quick and beautiful job. There's no need to do unnecessary exposure. In these kind of cases you have to handle the tumor, break the tumor, learn the art of breaking the tumor. Even ossified anterior foramen meningiomas I did anteriorly located, which are difficult tumor, as you know. This is completely bony tumor, bone, and vertebral arteries within the tumor. And you can do by selected midline approach rather than have this, have that. But you have to be very sure that you can. Another, see, see, ossified tumor, and having vertebral arteries in its midst and you have removed the tumor. This is another ossified. Difficult tumor, you can imagine. But you need to tailor your exposure according to your needs and according to your experience, and you can do beautiful neurosurgery. Neurosurgery is, of course, a passion of mine, it's a love of mine, and it has given me happiness, and it has given me depression with complication. You have to know exactly how to do and what to do with various tumors. In meningioma, you don't ever think that you can cure the tumor. Curing is a non-issue in meningioma. You remove the tumor radically and you remove the tumor effectively. Radical is the key word for skull base surgeons. You cannot say I'm a conservative skull base surgeon. You have to be radical. But radical does not mean out of your mind. You have to be philosophical, you have to treat the patient, and you have to treat the patient in a beautiful manner. Another tremendous sentence I'm going to give you, recurrence of a meningioma is independent of extent of tumor resection. You remove the tumor and nothing but the tumor. You cannot stop its recurrence. That will depend on the nature of biology of the tumor. It is not the treatment, but cellular behavior that will decide the outcome for all tumors. You have to be absolute. Neurosurgery is an absolute game of intelligence of the doctor. You can create wonders and you create disasters. Thank you very much, my dear Aaron. I hope I have been able to give some fantastic information. Thank you, Aaron.

- Really enjoyed it. Great work. Obviously there are different philosophies of how to do things, Atul, and I think yours has been a firm one in terms of the approach to use. Last week we had, or two weeks ago we had another lecture by Paul Gardner to emphasize that the only approach to cavernous sinus is through the nose. So I don't think one way is right. I think every surgery has to be approached through its own strategy, and one size does not fit all. I think that's the way to do it. And everybody's expertise is different. Some people may feel more comfortable to go through the nose for certain tumors, and some people may feel transcranial, extradurally. Some tumors can be approached either way, and some tumors can only be approached through one way or the other. So we have to be flexible. I think we have to remember that neurosurgery's a technical science that also advances as we go along.

- No question about it. You know what, we have to understand the tumor. My message is very clear, that you have to understand dural anatomy of the tumor, how the arteries are displaced, what is the vascularity of the tumor, what is the consistency of the tumor. Like for instance, like for instance, Aaron, I'll say. Like in trigeminal neurinoma, the carotid artery is displaced medially. I will say it is very dangerous to do it from the nose. Another thing I will say is, hemangioma of cavernous sinus, such a vascular tumor. First in 1991, I thought that it was a pituitary tumor and I went through the nose. I published that paper. And there was a tremendous bleeding, and I just packed it and rushed out. The histology came as cavernous hemangioma, and then I did transcranial approach for 1991. And I have no hesitation to say that no matter how expert you are in endoscope and all, if you are not diagnosing your tumor before operation as a cavernous hemangioma you enter into it, you can have a disaster at hand. Even chordomas. Chordoma is one tumor which is an extradural tumor, and transnasal route is quite a good approach for extradural tumor. Extradural tumor, nose is the best route. But you know what, some of these tumors go so much intracranial, some of the tumors so much in the middle fossa, carotid artery control may not be as good from the nose. Sixth nerve is very far away from your picture when you are coming from the nose. So all these things combined does not take away the beauty of transcranial route in a number of chordomas. So although I do some of these tumors from the nose, but there is a special place, as you rightly mentioned, for each tumor to understand and then do the operation. Aaron.

- I agree completely. Really enjoyed it. Thank you for being a contributor to this series. We look forward to having you again, Atul, and thanks again for all you do for neurosurgery.

- Aaron, what is the on various subjects like pituitary tumor in five minutes, trigeminal neurinoma in five minutes, hemangioma in five minutes, chordoma in five minutes. I will like to have an opportunity with you to talk on individual, like I want to talk on my experience on pituitary tumors as a separate entity. We'll discuss about all those things later. In any case, Aaron, it is my honor to be on your show. It has been my privilege, and you have given me this opportunity to take my message further into deeper corners of the world. Thank you very much.

- You're welcome, and thank you, Atul.

- Thank you.

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