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Grand Rounds-Percutaneous Procedures for Trigeminal Neuralgia: Radiofrequency and Balloon Compressio

John Tew

June 15, 2014


- Welcome, ladies and gentlemen, to another session of the Doubleness of the Grand. Our today's guest is Dr. John Tew from Mayfield clinic and university of Cincinnati Neuroscience Institute. He's a master surgeon. He doesn't require any introduction. He has been a great mentor for many young neurosurgeons including myself. He will be talking to us about indications, rationale, and technique and outcome for percutaneous procedures for Trigeminal neuralgia with a specific emphasis, on radiofrequency rhizotomy. Dr. Tew thank you for joining us and please go ahead.

- Okay, Cohen, how are you? Thank you very much. We're gonna start the discussions by looking at the first slide which discuss the treatment options. Of course, everyone knows that medication should be tried first for trigeminal neuralgia. And we will focus principally today on the surgical approaches that are, what I prefer to call ablative versus physiologic. Ablative procedures are largely done percutaneously either by radio frequency, injection of glycerol, balloon compression or occasionally radio surgery may be used also. Physiologic procedures where you do not cut the portion of the nerve or destroy a portion of the nerve by some type of physical measure are called physiologic. In my example that we were talking about today, and that of course is microvascular decompression. Choosing the treatment is very important. So, we talked about the physiologic is microvascular decompression. We will focus most of our attention today on percutaneous radio frequency treatment and glycerol or balloon compression with a preference for balloon compression. Radio frequency, as you know, is a selective procedure that uses a heating current it's kind of blank microwave in some one mega cycle current. And it selectively has the capacity to interrupt nerve fibers in various divisions of the nerve root. Glycerol injection does a destructive procedure also, but using alcohol and it unfortunately is not a selective procedure and it requires that one get into the cistern and achieve a flow of CSF. So in many cases where there's been previous treatments, there may not be the possibility of getting CSF flow. Balloon compression is a very good procedure for certain cases and it will be of course be discussed in more detail by Dr. Cohen. It's preferred by some people because it doesn't require the type of testing that is needed or essential and very helpful in using regular frequency. But it does allow you to compress the ganglion and some of the posterior root of the nerve and produce a selected lesion. In my experience, I prefer percutaneous radio frequency for these types of circumstances. Of course, when there's been a failure of medical therapy, when the patient has major medical comorbidities, or failure of previous MVD. I don't think there are many indications to repeat a microvascular decompression because the results are less good on the second occasion and the complication rate is considerably higher. The patients who have pain in the first division alone are not good candidates for radiofrequency because there is some risks to the corneal sensitivity. But unfortunately, that is something that we don't have to deal with very often. There's another example, a high indication in my experience and that's patients with trigeminal neuralgia associated with multiple sclerosis. These patients are very severely affected by the condition and many times they have comorbidities that make more complex operations difficult. So radiofrequency is a very good option for them. And of course, always, patient preference. Patients come to me frequently wanting to have a percutaneous procedure because they've heard about it and don't want to have a craniotomy, but we try to talk them into having the best procedure for their condition. But patient preference is always something to take into consideration. We are gonna talk about the six steps that we go through when doing a percutaneous procedure, whether it's for radiofrequency or for balloon compression. You would do many of these steps for either of these procedures. The first one is of course, to prepare the patient for the procedure. Use a Fluoroscopic C-arm and in balloon compression one would use an anesthesiologist or use a general anesthetic but in radiofrequency, we just use a very short acting or ultra short acting barbiturate called Methohexital and inject half a milligram per kilogram. So that's in general, very effective. We've tried another group of drugs, but find that Methohexital is by far the most effective. So the patient is placed in the radiology suite or attended in a outpatient operative facility and that's where we do most of ours now. And it's very important that they be awake and receive all the preoperative after pain, about four tenths of a milligram, so that they are able to wake up very quickly in between procedures. So you outline the landmarks, which allow you to place the needle exactly into the foramen ovale. One is the medial aspect of the pupil, three centimeters anterior to the external meatus and two and a half centimeters lateral to the commissure. So we place these marks on the patient every time, even though we've done thousands of these operations and the fluoroscopic set up is used, and this is a technique that we developed and discovered that you can use the lateral fluoroscope very effectively to guide your needle in place. So you want to see a good picture that defines the clival line and your trajectory is going to be cited right toward this point. We'll talk more about that as we go along. So you cannulate the foramen ovale by placing your finger along the lateral aspect of the pterygoid and guide the needle along that trajectory. We'll show more about this as we proceed, you angle that cannular toward the intersection of those two lines, one going from the tip of the nose toward the external canal and the other angle toward the medial aspect of the pupil. We'll keep coming back to this point. This shows it on a dry skull, how you guide your needle there with your finger tip. It's important to use a dental prop in the mouth so that it keeps the patient's mouth open and prevents them from inadvertently biting your finger during the course of this operation. So you see how it's guided right to that medial aspect of the foramen ovale. And that's important for a reason that we'll talk about later. So you use the lateral fluoroscopy and you're looking toward this point about five millimeters to 10 millimeters below a plane that intersects with the profile of the clivus and the floor of the cella. So Dr. Cohen, can we see the first video please? So this is another video actually done on a dry skull, and you can see that fluoroscopic image of the needle following the correct trajectory. So if you just make a fluoroscopic image right at this point you can see exactly where it should be going. So let's see the next video, please Dr. Cohen. So here we are actually doing a patient and you see the lock going between the teeth the nurse anaesthetist will inject the barbiturate. And when the patient is adequately anesthetized, which takes less than 30 seconds, a cannula is placed and the surgeon is guiding it in place. And here you see the lateral fluoroscopic image showing the placement and within another 30 seconds or even less, the patient is awake and cooperative again. Just reviewing the tips. The best target is the medial anterior aspect of the foramen a trajectory contacts the malar ridge just anterior to the foramen. So then you take a look with a fluoroscopy and then you slip the needle into the foramen just along that trajectory that you see here on the screen, there you go, okay. Now of course, there are some things to be concerned about. The carotid artery, the inferior orbital fissure and the jugular foramen, three areas that are important to keep in mind. Four is a trajectory way up here that's why the lateral fluoroscopy is so important. And three is the carotid artery all along here is the two is an area, and also one where the carotid canal begins at the foramen lacerum. And five way down here is a jugular foramen. So on this dry skull, and you can see in periorbital fissure there's a foramen ovale, foramen lacerum, jugular foramen and the carotid canal. So you have to keep your needle right here if you want it to slip into the foramen ovale right at that point. And using that lateral fluoroscopy, it is very helpful in getting you to that trajectory. Okay. so this is a simulation using MRI. It might be helpful to you, but it just shows you in three dimensions. First, the axial, then the sagittal and coronal how it progresses. So if you will run the video now, you can actually see what needle passes through at the simulation in three dimensions. So it's going along this trajectory toward foramen ovale. You see it passing through right here. It may be helpful for those of you who are watching to repeat this a few times, that you can see your stand point, your trajectory is the foramen ovale, and the trigeminal cistern right here. And of course the posterior root of the trigeminal nerve, we'll show that again in other slides that will help you understand that situation. And coming back to the slides, this is your trajectory right here in the lateral view. So you can see exactly how it outlines 5 to 10 millimeters below this point along the profile of the clivus. And in most circumstances you will get CSF. If you don't it still can be a very successful procedure. You don't have to have CSF, but it usually indicates that you've reached the cistern, deep to the ganglion and the fibers of the posterior root are organized densely third division, second division, first division. So we'll show how by use of the curved electrode, you can selectively stimulate and cannulate each of those fiber groups. It requires frequently an advancing of the electrode to reach the first division, but because we wanna spare the first division in most patients and not create a lesion there, we don't go into that area. So these are guidelines as this is an artist procedure, but this is generally how it works. So you see the ability to manipulate that electrode by pulling it back in and tilting the electrode upward, downward, medial or lateral. So the patient is awake when you use the stimulation and we start with a low current to titrate the current up, and you have very good patient interaction in order to get good communication and collaboration. So you should get a stimulation, usually around 0.1 volts. If it requires a large stimulation as much as a volt, that means that it's not gonna be successful because the electrode is not in the exact relationship with the trigeminal roots. That's why we enter the foramen ovale on the medial anterior aspect. So you see here, the electrode is placed inside the cannula. And again, by stimulating as the fluoroscopic view showing exactly where the electrode is located. Now, the patient will hear us asking questions about where they feel the electrical shock. So this patient says on the video that she feels it exactly in the mid portion of the base. So that's exactly where we want it in our case. And you can see that she's having a little bit of pain, it indicates that we're reproducing the pain with the electrical stimulus. So that's how we know that we're in the correct division and that we are getting a very good localization. So once we get that response, we put the patient back to sleep and make a therapeutic lesion. When patients are having severe trigeminal neuralgia, the stimulation may actually bring on an attack. So you have to be very careful about using a low voltage stimulation during this part of the procedure. And of course that's a concern with having the patient awake. This slide shows how we equate the intensity of the stimulation with the probe temperature that we would use to make a lesion more stimulus required as the voltage increases. It means that more temperature, to recording the temperature while you're making the lesion is appropriate. So we never take the temperature above 80 degrees centigrade that's just under boiling or under the point where you would make a irreversible lesion and actually coagulate the tip of the electrode. So these are the primary areas you want to work in around 70 degrees centigrade. So to produce a lesion, of course, put the patient back to sleep, measure the temperature and then after awaking monitor the sensory findings. And we do that by awaking the patient again, comparing the opposite side, the right to the left, sharp to dull and crossing over the midline and the patient being awake and carefully and very effectively identify the degree of the sensory loss. When it's hyperalgesia, analgesia or anesthesia, of course, you're seeking to get just a hyperalgesia or mark hyperalgesia. And we'll see in a moment how that is done. So let's look at the video now, please Dr. Cohen. So using a sharp, you watch how the patient reacts when you reach the mid line. You can see that. So she is identifying in a sharp in the forehand and much less sharp in both the second and the third division. And you also get the visual hit by watching the patient, and then the patient can compare the two sides. So what we've learned here that we need to make a little more lesion because the patient is sharper than I would like to see her in the second division. What she's doing now is actually quantifying the lesion, telling you it's 50% sharp in the second division, about 80% sharp in the third division, and 100% sharp in the first division. She is a very cooperative patient who helps us a lot with the procedure. So tips on lesioning, you reposition the electrode. If you need to stimulate again, and your testing should always be done in the autonomous zones. If you get into zones where you may be getting some innervation from other areas as is true over the nose or right in here. So the autonomous zone for one is right above the eyebrow to four underneath the eye. And for three is the lower, slightly away from the midline. So let's look at the lesion testing one more time. So this is the type of, she's telling us that it's normal in the first division and markedly hypalgesic in the second division. Okay, let's go back to the slides, please. Now, this is just a final testing to confirm that the patient has normal motor response in the trigeminal, normal visual tracking. So no cranial nerve deficits of 3, 4, 6 normal motor, and she's discussing the procedure and she actually says, if you can hear her it was not painful and she doesn't remember most of the procedure. And the nice things about the Methohexital is it creates an amnesia. So, there are some complications, temporary jaw weakness, and these are temporary signs, absent corneal reflex in about 3% of patients, temporary diplopia 1%, inflammation of the cornea and as in all procedures that are destructive, you may get patients who have anesthesia dolorosa but partial facial numbness is not a complication it's a high traded endpoint. It's an expected outcome necessary for pain relief. Patients have a tolerance for facial numbness. Most of them do not find it disturbing. There are rare mild disturbances and occasionally patients are troubled a lot by facial numbness. So you have to be very careful not to produce too much sensory loss. And that's one of the advantages of course, of less destructive procedures, but a principle advantage of this technique well done as shown in this case is you can calculate the degree of numbness. And as you see here, the degree of numbness is directly related to the long term effect on the rate of pain. Recurrence is much higher if you have mild sensory deficit and it is if you have major sensory getters, but it's still a very reasonable procedure to do, particularly in patients who don't wanna have any significant numbness. So the observations that I would say for treatment with all patients with trigeminal neuralgia, first is, you need to be absolutely sure about the diagnosis. That you're dealing with trigeminal neuralgia, that is not the typical facial pain. And of course the characteristics associated with a diagnosis are well known to most patients because they become very familiar with it. But with the passage of time and long uses of medication, hence sometimes even with other treatment, they forget what it was like in the beginning. So it's very important to go back and take the original history. And in order to be successful with the care of any patient, it's important to be optimistic and obviously a good listener. Perhaps one of the most important things we can learn is that there is no cure or trigeminal neuralgia. Every procedure that we use has some failure rates, and you wanna use the best procedure for each patient to be individualized. And Dr. Cohen will speak to that in detail when he discusses the technique for doing compression technique with the balloon. And unfortunately dysesthesia occurs with all ablative procedures and the more numbness you create with any procedure the more likely the areas for development of unpleasant sensation called dysethesia. Unfortunately, this dysesthesia is not responsive to additional ablative procedures. So that's important to remember. And it's essential to know, I think that the outcome of treatment worsens with chronicity. The longer the patient suffers the longer they take medication, the more likely they're to have a less effective result. And in my experience, some may disagree with this repeat MVD surgery certainly has a higher risk and less opportunity for success. That's one of the reasons percutaneous procedures are important to have as a part of your curriculum and in your program. And I know at the university of Indiana, Dr. Cohen does a lot of different procedures and can offer the patient virtually any type of technique, whatever is best needed for their type of pain and condition. So maybe we should talk a little bit about that Dr. Cohen, I appreciate your thoughts on that topic or others.

- Dr. Tew, thank you again for really a great nuances in terms of both selection and the technique. If you don't mind, I would like to echo some of the important points that you very eloquently mentioned. Number one is, trigeminal neuralgia has no cure and the patient should understand that from the beginning. Also, patient selection is the most important factor in the ultimate outcome. Patients should have good cutaneous triggers. Having some constant pain does not exclude them based on virtual classification, which I recommend to our viewers to review. And the character of the pain can change with medications and previous percutaneous procedures. So initial history taking, or really reflecting back how the pain was at the beginning is very important. Most importantly, very young patients younger than 40 years of age, when they have to have trigeminal neuralgia, you really have to have a request to complete workup tool, add multiple sclerosis or other reasons for their pain. As we know, it's really unusual to be very young and have typical trigeminal neuralgia. Let's say those are the pearls for diagnosis. When we come to selection, I think both you and me agree that microvascular decompression is the best way to go for most patients if they can tolerate surgery and they have typical trigeminal neuralgia. Again, going back to the diagnosis, if they have burning pain, if the pain does not have cutaneous triggers, and if the pain is in atypical locations in the face, that brings up very red flags that the patient may not do well with any procedure you choose. But let's say the patient is young enough to have typical trigeminal neuralgia to a younger than 70 or 75 years age. I would say both you and me agree that microvascular decompression is the best approach. Do you agree with that?

- Well, let me ask you one question about that. So we're very blessed today we're having excellent imaging techniques. So, if you do a specialized imaging like the FIESTA protocol and you don't see any evidence in a very good high resolution, MRI vascular contact, so the SCA or other arterial loops are nowhere near the nerve. Would you recommend an MVD for that patient or would you consider a destructive procedure like balloon compression or radiofrequency?

- Yeah, that's an extremely good question. You know, I would say if the patient is really healthy and are relatively on the younger side of the age factor general neuralgia, I still would go ahead and explore the posterior fossa because I have had patients that even on FIESTA, they may have had no vessels and we did find the vessels in tropadry. However, this will be another factor in the big picture that would lower my threshold for offering them an MVD if they're older. If there's any question about their pain, that is not typical trigeminal neuralgia. Again, decision making is not based on one factor it's many factors, which would lead us to believe what's the right choice for the right patient. And as you very well mentioned, is that's just one factor in the pool. You can't just define that, well, this is how every patient should be treated. There's an art to the practice of treating trigeminal neuralgia. But I would say if a patient is on the younger side for the ages of trigeminal neuralgia, which is, let's say 55 to 80 years old, I still would consider MVD. May ask what your thoughts are in that situation.

- My opinion is that, virtually anyone who is not anti-coagulated or he doesn't have to be maintained on anticoagulants can have an MVD. In fact, older patients who have some relaxation of the cisterns or have more cerebellar atrophy are actually easier to do and they do extremely well. So physiologic age is very important. I wouldn't rely any significant consideration to chronologic age because procedures are well done by experts and certainly you are one of those,

- Thank you.

- Operate on virtually anyone with a good anesthesia team and get a good result with the caveat that there is some evidence of compression. On the other hand, if the older patient has no evidence of compression on the image, I would use a ablative procedure.

- Let's say we decide that the patient should go under microvascular decompression and they do well. That's obviously a separate category. Let's now focus on patients who are a good candidate for an percutaneous procedure, either because they're not a good fit to undergo major surgery, like, you know, not a major surgery but MVD let's say, or because they're older or they prefer to do a percutaneous procedure or they have multiple sclerosis, which as we know, they're not necessarily a good candidate for microvascular decompression. I know you have been a pioneer in radiofrequency rhizotomy. I do the technique exactly like you described it and it works beautifully. There is no doubt it had made a huge difference in the lives of many trigeminal neuralgia patients. The way I have looked at it, if a patient is a candidate for a percutaneous procedure, I either do radiofrequency rhizotomy or balloon compression. I'm going to review at the end, the advantages and disadvantages of each, or maybe this is a good time before we go to the video, we can review those. I like radiofrequency rhizotomy because it's very selective. It definitely targets either B2 or B3 and you can immediately get a feedback that you did the job. In other words, the patient has numbness, very mild one, where you need it to be. It's somewhat milder than balloon because the balloon is a little bit non selective. So I would say radiofrequency is a very effective procedure. What I'd argue against the radiofrequency rhizotomy, is that number one, sometimes patient comfort can be important. And even though most patients have amnesia, if they are somewhat demented, if they can't tolerate pain of any capacity, if they're not co-operative for other reasons, they may not be a good candidate for radiofrequency rhizotomy. Number two is what about a patient who has a V1 trigeminal neuralgia? I think balloon is an excellent procedure or a glycerol rhizotomy. Number three, which I would like to ask your opinion. What about if the patient who has trigeminal neuralgia in all three divisions, how would you argue about those points that are disadvantages of radiofrequency rhizotomy?

- I think your points are very well taken. If you have isolated pain in V1 that's one or 2% of all patients, one thing you can do is just a peripheral neurectomy. And many of those patients do extremely well with that simple procedure. If there are three division pain, I think a percutaneous balloon procedure is a very reasonable option because you get all coined divisions and you spare technically the sensitivity of the cornea. So in my understanding, I would certainly agree with you. It's a very reasonable option. I think another example would be patients with multiple sclerosis. So balloon compression is a very reasonable option if all three divisions were involved, but you wanna be sure in those patients that you don't create too much sensitivity loss, because they may have pain develop on their opposite side. So I certainly agree with you that every center, everybody who has an expertise in trigeminal neuralgia should know how to do one or both of these ablative percutaneous procedures.

- Now that we talked about the decision making process for microvascular decompression or a percutaneous procedure, I think there are a group of patients who are a reasonable candidate for radiosurgery rhizotomy. And although I personally, I have had a less effective response for radiosurgery rhizotomy, I'll do all three procedures. I feel that the efficacy of radiosurgery is about 60 or 70% of the patients and it's definitely less than microvascular decompression and in a percutaneous procedure, especially if the patient wants to come off of their pain medications. Therefore unless they have significant medical comorbidities that prevents them from undergoing an invasive procedure, I have gone either the route of MVD or a percutaneous procedure. Has that been your experience or it's been otherwise?

- I think about the only real indication for there are two indications for radio surgery. One is the patient in the opinion of their trading position cannot come off anti-coagulants or even for a reasonable period of time 48 hours or whatever, to allow them to undergo a percutaneous ablative procedure. And the second is patient preference. And then there are some people who just don't want to have any type of invasive procedure. And of course, either the procedures are done with needles are invasive and there are some individuals who don't wanna have it. So, there's definitely a place for radiation. I think it's very small. My criticism is that too many patients get radio surgery, even for conditions that it should never have it for, like shingles, post herpetic neuralgia and all kinds of things that I fear because it's too easy, it's just doesn't require the type of technical skills it takes to do a balloon compression, for example.

- Have you been using radiofrequency rhizotomy for post herpetic neuralgia since you brought it up? That's a very complex topic of its own.

- No. No I would definitely not recommend or ever consider doing a percutaneous ablative procedure of any sort for post herpetic neuralgia.

- I agree with you completely. If you don't mind, I'm just gonna review a few nuances that has worked for us, probably it's gonna really echo what you very well mentioned and then we're gonna review a video of a balloon compression rhizotomy and get your opinion about that technique, in general. Remember the advantage of the balloon compression rhizotomy potentially over radiofrequency is that patient comfort could be more because the patient is done in the anesthetic. It is a much, at least in our hands is a faster procedure. It takes us less than five minutes from the moment we penetrate the skin and we have had very good outcomes without necessarily too much numbness or other complications from significant ablative techniques on the nerve. So I'm gonna review some of those with you, and again, get your expert opinion. I think the setup for the room is very clear and you reviewed them very eloquently. I would like to take a moment and just emphasize the importance of a fluoroscopy. You mentioned that the lateral fluoroscopy is critical. No doubt. Nobody should do this procedure without fluoroscopy. What we have used is by extending, besides using laparoscopies also using the fluoroscopy through the or parallel to the angle or access of the needle. In other words, you have the fluoroscopy arm turn, you extend the neck of the patient and the head and you turn the head contra laterally. And this gives you a bird's eye view through the needle for us to be able to see where we are compared to the foramen and has really been very very effective in giving us another, let's say, confidence factor to make sure we're close to the foramen, because even though natal for us could be gives you an AP and lateral correction. The accurate lateral to medial trajectory can be somewhat confusing, especially in patients with a very small foramen or those patients who have a sort of a ridge a bony ridge in the foramen. So, and I'll show you the video what the picture looks like. And I wanna emphasize this technique for our readers, especially for those who are novice neurosurgeons at this technique that using another localization technique can be quite effective in getting the needle in there. So the two and a half centimeter rule was very well mentioned by you. Obviously this is a radio frequency needle described by yourself and invented by yourself. And then as you can see, the needle is along the medial edge of the foramen flint with contact to the nerves of the trigeminal nerve or the roots of the trigeminal nerve. You can see, obviously, the degree of angulation and the distance from the cella, those were all mentioned by you. I think the angulation of the needle dorsal are reviewed. And so after this is done, obviously the patients go home same day. There's no need for inpatient hospitalization. And one of the details about a glycerol rhizotomy, which I have personally not used is the need for a sitting position. I think glycerol rhizotomy may have potentially slightly high risk of pain recurrence. Although when you read a lot of different studies, there has never been a randomized trial. There's never been a clean study to compare percutaneous radiofrequency rhizotomy to a balloon compression, to a glycerol rhizotomy. So, we don't have ultimately the clean data that could tell us which procedure is better, but overall, what has been my practice is I start with a balloon compression rhizotomy. Sometimes patient don't get relief in that could be that their gasserian system is very large and the balloon just cannot sit in the right position to compress the gasserian ganglion or the fact that it's so tight that it cannot even inflate the balloon in the cistern. Therefore I'll bring those patients back with a radiofrequency rhizotomy and we have had a very good results. And again, you have to gauge what works for you and stick with it. Do you have any comments before we go to the video Dr. Tew?

- No. I agree with your approach. I only use the lateral philosophy and using those techniques that I described, it's very easy to get into the foramen and in also in this medial anterior part. But obviously I have a lot of experience. So if the individual feels more confident using an oblique view with the fluoroscopy, I think it's perfectly okay. I certainly don't think you need to use a stereotactic system or an MRI, like some people recommended.

- Yeah, I agree. So let's go ahead and review this video. I wanna make a differentiation that the balloon compresses the gasserian ganglion. So it's at the level of the ganglion or radiofrequency rhizotomy is at the level of the roots of the trigeminal neuralgia. There is a big difference between the two. So if you put your needle over radio frequency and you're not exactly a double over the roots, and you're more, you may actually get an exaggerated pain response and it tells you that your needle is not that the right position. So let's talk about percutaneous trigeminal ganglion, balloon compression rhizotomy. In a case of a 72 year old male with V2 and V3 trigeminal neuralgia. The setup for the room is very classic. Again, we emphasize the importance of fluoroscopy. And you can see in this video, we use a ruler to measure the distance about two and a half centimeter with stabbed incision to create a nice entry for the needle of the balloon, which is larger, and then we obviously make sure the needle does not perfoliate the mucosa meatus. And now we go ahead and as you can see here, I just hit the angle of the mandible to make sure I'm on the right trajectory. And then I angle the needle more medially. And that gives me another view of how things are in relationship to the foramen. You're going to see momentarily. We're gonna have an overlay view on the skull, which will just give us an idea where things are here, again, passing the pterygoid. And here's the view of the surgeon, if you have a skull, we wish every patient had this sort of view and with their skull sort of overlaid on their head. And you can see for a surgeon how the angle is it's again, medial comphis, just like you mentioned, and it's three centimeter anterior to the ear, and that's the view. So you want to have that in mind as you're advancing your needle. Obviously you don't want to hit the carotid artery or the jugular vein to avoid any complications in that area. So we'll go ahead and again feel the angle, we'll go ahead and place in the needle and we'll go ahead and do a lateral fluoroscopy. And in this situation, you can see that again, I pointed at where the clivus and a petrous bone, meet each other. It's really where we want it to be. And after I get that lateral view and gives me an ideal, more anterior and posterior trajectory is satisfactory I'll go ahead and do the oblique view through the fluoroscopy that you very well mentioned, which would give me an idea as you can see here is the fluoroscope moving in a new position, the patient's head is turned Contra laterally and extended. And here is the view of how the fluoroscope should look parallel to the needle. And here you can see the foramen clearly there's no way you can miss it, especially in this case. And it tells me that I have the right anterior to posterior trajectory. I'm sorry, lateral to medial trajectory, but on a little bit posterior to the foraamen. So I just have to advance my needle just anteriorly and maybe slightly medially. And I'll be right in the foramen. And here is after repositioning of the needle. And you can see on the sector view of the fluoroscope in the oblique view, that I'm definitely the foramen. There is no doubt about it. There's no questions. It really is a confidence builder, especially for the beginners that there are definitely in foramen ovale. Here is advancing through the foramen and across the skull base. I usually bring the needle backwards to be as close to the skull base as possible as you can see here, because I don't want my balloon to be insulated over the Pitsa switch, and here you can see CSF. That's always a nice confirmation that again, I'm where I need to be. We pass the stilette to create the pathway for the balloon, which is obviously deflated in this situation. We go ahead and advaance catheter and go ahead and inflate the balloon under live fluoroscopy, or getting multiple images at the same time consecutively. And you can see the balloon gets inflated, and you can also appreciate almost this sort of little indentation or you say elevation that tells you that's a V2. So we're right where we would like to be we're in gassarian cistern. You can see sometimes the balloon can go over the Pistra switch if it's inflated too much, but here is really V2 as it interrupts the foramen. And obviously we're in the B3. So that's a nice placement of the balloon. I have to emphasize that if your balloon is too high, it's going to go over the pistra switch and you will not get a good balloon compression for the gassarian ganglia. And that's really critical,, the shape of the balloon. There has been multiple studies there. You don't want to be too high. That would also potentially can cause double vision by compression of the nerves in the cavernous sinus. You want to be as close as to the skull base, as you can but not too close, that necessarily your balloon would not inflate. And we usually inflate the balloon for about a minute, a minute and a half and then it's deflated and x-rays performed to assure that everything is deflated and then the whole apparatus is removed and we're done really five minutes. Patients leave very comfortable and we have had very good luck performing this procedure with minimal complications. So if I may ask you to have the closing statements Dr. Tew again, I appreciate your time.

- Okay. Well, I think we have a very nice discussion here about techniques that are available, they are essentially two techniques, ablative and physiologic. And we all know that we want a physiologic procedure if we can achieve that. And if it is the best in the interest of the patient and choosing an ablative procedure, I think we have lots of options, but we agree that a needle procedure is preferred and there are two extremely good options, either radiofrequency or baloon. I personally prefer to use the radiofrequency first, rather than the balloon, because I think it's a more, I would say, a little more selective procedure that allows you to get a single division or two divisions, which is the circumstance in most patients, the majority of patients, 65 to 85% have pain in either the second or third division or both. So it's a very nice technique. It does have the disadvantage of requiring or utilizing patient collaboration. That's an advantage and the disadvantage, whereas the balloon compression procedures is not selective it allows attention via sleep. So there may be some patient preference for that. In terms of timing. I think I can do a percutaneous radiofrequency in 15 minutes. In fact, I can do seven in afternoon with the turnover. So the timing or the amount of time required to do it is not an issue, but certainly there's no question that it does take more, I'd say experience and more study to do it well than a balloon compression. But obviously as you pointed out, you've got a lot of experience and, you know, exactly what to do. I wonder if there is any concern about hitting the carotid or corneous sinus. So are there any serious complications that might occur with this procedure? Of course, some of our colleagues have had some major problems with the placement of needles for radiofrequency which is carotid injuries, aneurisms omissions and even carotid artery ablations. There are some serious complications with all of these procedures as you have outlined it, and we have discussed the careful procedural techniques, I think that has very very low complication rate and a high level of patient satisfaction with both of these procedures.

- I agree with you. I've done about 300 of these percutaneous procedures so far, and I can tell you that I have hit the carotid artery once. And it's very dramatic, there is no question. The flow of the blood would shock you because especially we've never seen it before. And we just withdraw the needle and woke up the patient. The patient was intact. We did a CT angiogram to exclude a fistula or a pseudo aneurysm and repeat another scan in two weeks. And the patient did well and miraculously, her pain went away as well. And that probably was because just entering the foramen you injure the nerve. And that was just good enough. So as I've always said, and Dr. Roberto Harris once told me that the best quality of the surgeon and the most important thing, number one, is to be lucky. And I'll tell you, I have been lucky personally and that was a pretty dramatic case of hitting carotid artery with a needle, but that's a risk with any percutaneous procedure. I don't think you can rationalize that, you know, balloon has more than radiofrequency or radiofrequency more than balloon. But you have to understand if you do enough of these, you will surely have complications.

- Okay, great, Dr. Cohen, this has been a lot of fun. I think anybody who studies and works on this video and this study that you've put together here, will appreciate the opportunity to learn. One of the reasons I like to do this with you is it creates a procedural opportunity for people to learn how to do these techniques and obviously put it together very nicely. And so, individuals have no excuse now not to learn how to do these techniques and to incorporate them into their practice. So thank you very much.

- Dr. Tew, thank you for being a great mentor for so many of us and truly thank you for what you have done for neurosurgery. Thank you again.

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