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Grand Rounds with Dr. Jannetta: MVD for Trigeminal Neuralgia

Peter Jannetta

February 19, 2011

Transcript

- Hello, ladies and gentlemen, my name is Aaron Cohen. I would like to thank you for joining us for another session of AANS Operative Grand Rounds, which we'll discuss technical nuances for Microvascular Decompression Surgery for Trigeminal Neuralgia. We have Dr. Peter Jannetta as our discussant who will review our presentation and my surgical videos. Thank you. Well, Peter, thank you again for joining us. We really do appreciate your thoughts about MVD and your experience in terms of enriching the presentation today. This is the disclosures for our participants, none of which interferes with the presentation content today. So general neuralgia affects the patients in many ways, causing a very disabling pain. And as you can see in this picture, which is very well illustrating, the amount of expectations that patients have and how they sorta always worry about when the next pain would occur. This is the first picture that we could find at Yale university that Harvey Cushing took from one of his patients who was suffering from Tic Douloureux. Again, illustrating the intense pain that the patient is suffering.

- That's in your book. And I think it's the only trigeminal neuralgia patient in your book, if I read it correctly.

- It is correct, thank you, Peter. This is a hand-drawn sketch from Harvey Cushing himself, again, showing a right-sided avulsion, ganglion avulsion for trigeminal neuralgia.

- And that was found of course, to be not necessary.

- Yes, thank you. Trigeminal neuralgia is a relatively easy pain to diagnose. MVD has been one of the most satisfying operations I have performed, and the anatomy is really so pleasing to the surgeon and it's a relatively short and efficient procedure. The microsurgical environment is very much bloodless and most important, the patients do very well and they're thankful. As for general neuralgia, it's one of the worst pains humans have been afflicted with. Really relieving the pain is really one of the most satisfying parts of neurosurgery and the procedure in experienced hand is associated with minimal side effects.

- Our patients usually in one night, sometimes two, morning patients go home the next afternoon, the afternoon patients, the following morning.

- Thank you.

- They feel better, if you get rid of their pain, they feel wonderful.

- I agree. Trigeminal neuralgia, as we all know, isolated to the three divisions of the nerve. It's convulsive usually, it has its cutaneous triggers, including oral and skin triggers. And it responds to Tegretol and antiepileptic medications, and this is actually a good prognostic factor, both the surgery, for surgery to be effective as well as to diagnose the typical trigeminal neuralgia, if the patient responds to Tegretol and Neurontin favorably. One neurolysis that the character of the pain may change with time, especially used on neuropathic pain medications, epicutaneous procedures, and therefore a detailed history taking is important to realize what was the character of the pain at the initial stage of the pain and where the pain initially started.

- May I comment on that? The nerve, clinically gets stretched by arteries, especially that may give you constant pain. If you have constant burning pain, you've cut off the mountain peaks, you increase the drug, it will often get rid of that pain.

- Thank you.

- But then they can't tolerate it, which is one of our common indications for needing an operation.

- Thank you, and patients will have very much predominantly facial numbness and have burning pain and neuropathic pain. All these are not good candidates for surgical intervention.

- Many of these patients have a nerve that's been injured, and we depend with microvascular decompression on the nerve to heal itself.

- Yes

- And the others are a large number of patients who are put in the wastebasket, who are so called atypical facial pains, who are truly nervous intermedius neuralgia. We're seeing, we're understanding more about that all the time.

- This is a consultation that was recorded by Dr. Burchiel. Again, showing the two features that are called typical trigeminal neuralgia. And sometimes they may have, the patients may have a good portion of the pain being constant. However, they have to have a predominant feature of their pain to be episodic and convulsive.

- We have simplified this a bit. There are people who are concerned. The Trigeminal Neuralgia Face Pain Association about being dumped in the wastebasket of being of psychological origin. And a lot of this means we just don't understand those who are called atypical or atypical face pain, or atypical facial neuralgia. I think that we're, we're broadening the Gaussian curve by understanding more about what happens to the trigeminal system and what happens to the sensory facial nerve, in these patients.

- Thank you, Medication and the first mainstay of therapy, surgical therapy involves physiologic and ablative methods. Microvascular decompression is the only method that does not injure the nerve necessarily and provides a more durable response. A percutaneous procedure, glycerol injection, balloon or ready surgery may be other options. No matter what the responsibility etiology, MVD is the most effective and durable palliative option. Percutaneous procedures are less invasive. However posterior fossa exploratory surgery offers the only chance for a non-destructive procedure and more durable result. And as you very well have mentioned, Peter, in the past, in your talks, is everyone who can afford medically to undergo surgery should have a look at their nerves.

- I think that's almost the first line after medication and they do better.

- Thank you. Brain MRI and CT scan is necessary before a patient undergoes MVD, just because meningioma, acoustic neuroma, an epidermoid in the CP angle may have trigeminal neuralgia as their own presenting symptom. And therefore you don't want to do a craniotomy and find out without preparation that you have to deal with such tumors. If a high resolution MRI, and we're talking about thin cut CISS sequences from MRI, still shows no vessel, I do believe that posterior fossa exploration, is reasonable, because we have found vessels among patients who had a very clean or MRI evident, clean root entry zone, but harbored vascular loops during exploratory surgery.

- Arteries often medical or veins or both. So that your scans are screening other things, your perspective is the right perspective.

- Thank you. This is an MRI again, showing the vascular loop against the trigeminal nerve on the right side. This is one of the typical findings you find in trigeminal neuralgia patients. Thank you Peter. What are the indications for MVD failure of medical percutaneous therapy if the location of the pain is V1 where we really want to avoid any injury to V1, to protect the cornea. MVD may be a more reasonable option as a first mode of therapy after medication. And there's no perfect procedure for trigeminal neuralgia. It is important to realize that every patient's treatment has to be individualized, and there's no cure. What is most important is that the surgeon and the clinician has to be caring, has to listen carefully and has to stay optimistic. There is an art in dealing with patients with trigeminal neuralgia that have suffered pain for many years, horrible pain. And what we should keep in mind is the famous saying that "We cure a few while we comfort all our patients."

- All right, that's all they could do till 1915.

- Okay, Peter, if you'd be so kind to go through your slides and tell us about your nuances.

- Here's the lateral position, and you will change the angle of the next agency in the upper or the lower cerebellopontine angle. There are different ways of applying the head holder, but what suits you best is what you do. And what you want to do is to be able to have room, to see that this is for a hip nerve or a severed nerve, be able to see around the other nerves by looking down or up. Next. The incision to be a figure wrapped behind the hairline, to be more posterior in a large, long head, to keep the soft tissue out of the way and help you with your angle, looking in, it has to be, it can be more anterior in the small round head, but the deal is that you're going to go through the parameters here that we all go through to for good exposure. And if I could have the next slide, we'll go on onto that, the angle of incision will help. The self-retaining retractor. Aaron has often made the point that you must place your incision, and he uses a curvilinear, and he will show us that, to keep this tissue, not at a mass, but out of the way. Sometimes fish hooks will help you here. Here's the 80% situation. artery, often with the bifurcation distal, and you can have just a matter of branch. And if you don't see that nerve with the brainstem, you can miss this branch, put us in real trouble, Next. The root entry zone of the fifth nerve goes out to at or near Meckel's cave, recent studies had a dozen go to Meckel's cave. I think there may have been, these are pickled cadavers, but I realized that that we don't have a two dimensional cause if we have something this distal, they're three-dimensional. So even though it's at Meckel's cave, it can be coming in over this area. There are 100 fascicles here. There's 65 of them. about here, Davidson Haven, 1923. And every one of those junctions with this central myelin is a root entry zone and anything there or proximal poses hyperactive symptoms, next. This is a Mark McLaughlin paper from our cases of Tic showing a long loop and you go all the way down to AF, I've seen it down to nine and 10. And with careful rolling of an implant from proximal distal, this will pop the artery out into a horizontal position. It looks impossible, you have to be patient. If they have had a destructive procedure, the artery may be inherent to the nerve if they've had it for a long time, maybe inherent just be careful, take your time, and you'll get it in the horizontal position. Next. Instruments with a handle, large enough for a normal size hand, you don't need to have a micro handle for microsurgical instruments, next slide. And we don't use 90-degree hooks. You don't need it back there. I think they're dangerous. You already went with a 45, next, Shredded Teflon felt Ours is shredded. We're trying to get it made commercially because they hate to do it. Some people will use a block of Teflon felt, which is hard and gets harder and can act as a secondary missile. But you've got to shred it with a hemostat or a Kelly and make the different size, or submarines or cigars that you need, next.

- Thank you, Peter, for those thoughtful nuances. We're going to go over a animation just to show the approach. This is the right side at MVD where the bony removal in the suboccipital area and part of the mastoid bone, the sinuses are exposed. We go around the cerebellum, gentle retraction, the nerves are exposed, the vascular loop over the fifth nerve has been identified. The vascular is mobilized and a piece of shredded Teflon is placed between the artery and the nerve. This is again the set up of the operating room that we have come to use. again, patient remains in the lateral position and the assistant or the surgical technician is against the surgeon across from the operating table, handling the instruments. This allows easy transfer of the instruments that is unimpeded and the fellow or the residents is on top of the head of the patient. And then the ultra microscope comes over the head of the assistant. We have come to realize, using lumbar puncture has been very useful in decreasing the tension in the posterior fossa, as you go around the cerebellum, therefore, as we're placing the patient in the clamp, we asked the resident to place a Lombard drain needle and drain about 30 or 40 CC, we just attach the container with a tape. And by the time we go wash your hands and come back to drape, we ask one of the assistants in the room to remove the lumbar puncture needle. And we have not had any complications with this and have really enjoyed the amount of decompression it provides.

- Those the actuary role of protecting the downside Exelon in that drawing.

- Yes, it's right here, Peter, thank you. The head of the patient is placed in a clamp. There is various ways one can put the head in a clamp. I think Dr. Janetta has used the pin pinned right above the ear and the two other pins above the contralateral ear. We have come to use this method where the pin is frontal. The other two are more acceptable and posterior temporal and had this create a nice working distance for the surgeon. The head does turn a little bit contralaterally, and that helps you with going around the cerebellum. Positioning is very important in posterior fossa surgery, and you want the shoulder to be full, pushed forward and rolled forward, so it is out of the working zone and the arms of the surgeon.

- We use now more APs than even this drawing.

- Okay, thank you.

- Sure

- Let's talk about the positioning video. This video shows the clamp as the way it's traditionally placed and described by Dr. Janetta. The two pins are both above the ear and a single pin on the AC lateral side surgery. And as you can see, the pin stays above the ear, it provides a working distance and the other two are above the ear and outside the temporalis muscle. The patient is placed in a lateral position, the shoulders pushed forward. And that's the, working, distant... This is the pins placed on the frontal area and the two pins in the occipital and posterior temporal area. The clamp is angled across the long axis of the head. And this method really prevents this single pin to be even further away from your working distance in the suboccipital area. Let's go through some of our illustrations to further depict the nuance of technique. This is the position of the patient. We have come to use more of the curvilinear incision for two reasons, Number one, it may avoid some of the vascular tear that may be cut with the linear incision, as some of the nerves may be spared. And therefore the chance of neuralgia could potentially be less, although the linear incision works just fine. As you can see the relationship of the curvilinear incision to the tip of the mastoid. And we draw a line from the inner ear to the root of zygoma, and that defines the transverse sinus approximately, and the curvature and the sort of summit of the marking comes just above to that presumed transverse sinus location. We then, these two illustrations, as you can see, illustrates the advantages and disadvantages of each linear versus curvilinear incision. In a linear incision that you can see here, in a cross section this is a bones sinus, a little bit of bone has been moved over it. When you retract with a cerebellum, some of the tissue may be bunched up here and that can create a longer working distance for your retractor. And you may require a longer incision to get that far medial. However, it's a linear incision, it's easier to open and close. However, when you do a curvilinear incision, it pushes your scalp muscutaneous flap inferiorly and therefore the retractor may come over the scalp and there will be a smaller working distance to work through. The next slide, you can see the corridors we used, the superomedial for the trigeminal neuralgia and more of a inferomedial for hemifacial spasm. As you can see, the Burr hole is placed right along a point with this, which the point is defined by a line or the cross section of a line. The first line is the line that connects the inner ear to the root of the zygoma. And the second line is parallel to the mastoid group. Where they join each other, that's really the area where we placed the initial Burr hole to expose the transverse-sigmoid junction. Where a Burr hole was placed, and we usually turn a craniotomy if the dura is not attached. And as you can define the transverse-sigmoid junction very well, you'll be able to know where both sigmoid and transverse sinus are, and that would really provide you with a good localization and a small craniotomy just where you need it to perform the operation. Peter, may I ask, do you prefer a craniotomy or a craniectomy?

- Craniectomy cause I've seen some grief with laceration of the sinuses, with the craniotomy. and also with an open space, unless you fill in the holes. A problem with chronic headaches, which we don't have at all, if you cover the opening entirely.

- Thank you. Again, a Burr hole, the drill mate used to burn more of the mastoid bone in order to expose the edge of the sigmoid sinus. It's really important, especially on the outer cortical bone of the master to drill the bone as much as possible. So when you reflect the edge of the dura, superiorly and laterally or laterally, you are not getting hung up on the edge of the bone to maximize your exposure. Kerosenes may be used to carefully remove small pieces of bone over sigmoid sinus. For older patients, especially, the sigmoid sinus may be very much attached to the wall of the sinus and the sinus may be embedded into the bone and much care has to be exercised. Also, if there is a small laceration of sinus, a piece of bone wax may be placed along the hinge between the mastoid bone and the sinus to carefully cover the laceration. I think just pushing a lot of gel foam in there may thrombose the sinus, and that will not be a, a reasonable option. Again, the mastoid air cells well are well waxed as mentioned by Dr. Janetta, when a mastoid, I'm sorry, bone wax is used, as you can see, the mastoid air cells may extend superiorly and inferiorly, well said proverb by Dr. Janetta is "wax in wax out" So wax in as you're on the way in, opening the dura. And also re-wax the mastoid air cells on the way out. We opened the door along the edges of the dural sinuses, small sliver of dura is left to protect the sinus, number one, and also to be able to tack up the edges of the sinuses. As you can see in this illustration, this is lifting the edge of the sigmoid sinus with this attached dura. This is at the level of the junction, and this is at the level of transverse sinus. Entering the posterior fossa is the most important part of the operation, and the most difficult one and the most dangerous one, in my opinion. And as you can see, the surgeon has to orient himself, identify the tentorium, which is soft, the petrous bone, which is obviously bony, and at their junction, transfer at the juncture, tentorial petrous junction, follow and keep that junction in mind, stay on the petrous side. If you continue to junction medially, you're going to run into this superior petrosal vein, and you don't want to tug on it and cause an avulsion injury. Orienting yourself and going around the cerebellum is critical. What is also very important in terms of the nuance that Dr. Janetta has described is using this rubber dam. A piece of glove that is used underneath of a proper sized cotton rod, and as you go around the cerebellum, you can use a gliding action over the glove and rubber dam to prevent any injury to the cerebellum.

- That's important. I think rubber doesn't stick to tissue. I started doing this 'cause I had a plastic surgery rotation as a general surgery resident, and they use plastic surgery all the time. We put a stitch through it, we cut it shorter so it's not in the way. And it works very nicely because you don't have to take the cotton rod out to move it, you just slide it.

- Thank you. The arachnoid membranes are opened and the tic scissors are always kept in mind. We try to preserve the veins and the superior petrosal vein as much as possible, although it is reported that taking this vein is, is without any consequences. I do believe it's surgeon's responsibility at all times to keep normal vasculatures intact, if possible. The sectors are used to dissect the arachnoid before the micro scissors are used to cut the vessel, cut the arachnoid, because you really want to avoid cutting any vessel that could be entangled in the arachnoid membranes and often in this small working space, If you don't have an appropriate angle, curved micro scissors, cutting the arachnoid blindly could catch one of the vessels in the tip of the micro scissors and cause vascular injury. Any thoughts, Peter, on that topic in terms of nuances or arachnoids?

- Do not, as you say, do not cut what you cannot see. And I like to use curved scissors for most work back here as a point and you'll show us this later, is a very nice dissecting instrument, and you can see what you're cutting, much more favorably than straight scissors.

- Thank you, and you can see these are variations of vessels versus the nerve or what we call the neurovascular conflict. The most common one is the superior cerebellar artery curving along the axilla of the nerve. Peter, can you share your thoughts on these variations with us?

- Yes, those 80% of the patients with superior cerebellar artery, they may have an associated thing. Young women with isolated V2 pain are prone to have a distal vein crossing a nerve, could be the aberrant dandy's vein. aberrant inferior petrosal vein. This is B123, or B2. Veins on the surface should not be taken because they recollateralize. That's our most important cause of recurrence and arteries can be mobilized into a different position. And that's what you got to do, see everything, preserve what you can and take what you have to take.

- And you also mentioned that if there is a vein that's sitting on the surface of the brain stem, you do not sacrifice that.

- They collateralize, this is something we should learn about. Maybe we can grow the legs and arms on people because there's something that makes those veins go back right where they were.

- Okay

- And one month to six months, 4 times a year

- Thank you. And a shredded piece of 10 pieces of Teflon in small pieces are rolled across the artery and the nerve all the way to the Meckel's cave. Using the smaller pieces of shredded Teflon is important for two reasons. Number one, it allows us to place it in small spaces and decompress the nerve thoroughly, and secondly, because the small pieces mold to the area where they may be sitting into it may delay, or it may prevent their delay displacement. So we do use, as you mentioned, Peter, the small pieces of Teflon are shredded and rolled them across the nerve, piece by piece between the artery and the nerve.

- That's important, the people using a cut brick of Teflon felt are not doing a patient a favor by frequent...

- Thank you. This last piece of Teflon is placed just in the axilla and sort of lodges right there. And we'll make sure that is not displaced by lodging the dividing of axilla between the arteries in there and the axilla region of the nerve. And this is where the final results showing the complete, the compression of the nerve all the way from the root injury zone to the Meckel's cave.

- Outside of the loop was pressing on the nerves with every pulsation, now the arterial loop is just lying on top of itself, there's no compression.

- Thank you. This is an intraoperative video of one of my cases again, showing the nerve, the artery, the vein and left sided, retromastoid exposure. And the Teflon has been placed between the vein, and the nerve, the nerve and the artery, all the way to the Meckel's cave to assure no compression is present.

- That's very clear.

- And then this is really what, Peter, you described as venous compression along the nerve entry zone. And for those that are really covering the brainstem, it's better to preserve, and for this one, for example, we're just sitting on the surface of the brainstem. We tried to microsurgically dissect it and then put a Teflon patch and decompress rather than coagulate and cultivate.

- I think that's important, if a vein is more than half the diameter of the trigeminal nerve, I decompress it, in every case. On the surface, I do everything I can to keep from taking it.

- Thank you. This is a rare finding of hypertrophic bone of Petrous region, petrous bone region that overhangs the nerve. This is again a right-sided retromastoid approach. And it prevents the surgeon from seeing everything along the nerve. And after we remove the bone using a drill, you can see a compressive vessel was identified. And therefore it's important that if a surgeon cannot visualize the entire length of the nerve to remove a little bit of bone, especially in these cases to increase visualization.

- Kama Kali, one of my residents first really showed this and I call it Camel's hump, but you can see under there with a mirror, we're not taking the bone and somebody's going to be coming in and going out. The other point that I think is important is that this part of the nerve with distal compression, especially caudally can be very soft and you can injure the nerve if you're not careful about decompressing it.

- Thank you. This is an MRI of a challenging MVD case. You can see this is an older patient, a very ectatic basilar artery compressing the nerve, really impressive case of neurovascular compression. He underwent multiple percutaneous procedures. He was about 75 years old, and ultimately underwent an MVD procedure. We're going to show the video momentarily and you can see the nerve very much pushed superiorly. And these patients with such minor compression, medication and often percutaneous procedures provide limited, if not short lasting relief and mobilizing such a vessel can be a big challenge. And we'll go over the video and I will be interested in Dr. Janetta's expertise regarding the findings in these patients. So let's go ahead and review our surgical videos. Well, this is a left-sided craniotomy for microvascular decompression. You can see the mastoid bone, the ridge and the suboccipital bone, the curvilinear incision, the Burr hole has been placed right at the juncture of the groove to the presumed, connecting line on the inner ear and the root of the zygoma. Kerosenes have been used, this is under high magnification microscopes, so the viewers can see everything better. You can see the edge of the sinus. You can see how it curves around the transverse sinus curving into sigmoid sinus. What happens if somebody gets into bleeding there and they have injury, Peter, what would you recommend?

- Something on the surface, I know you used bone wax. I'll use a piece of Surgicel with bone wax over it and just push it under there, may add some hydrogen peroxide, and then just let it go, it would be, it will stop by the time you're working on the way out.

- Okay, thank you. Here we're trying to dissect as thoroughly as possible, both the transverse sabina sinuses, as well as the dura. If one places the Burr hole and injures the sinus, Peter, what's your recommendation at that point?

- I'd put the bone wax on it and do another Burr hole.

- And for the put Burr hole, I guess more inferiorly and medially...

- ...posteriorly, yes

- ...and just, just bite the bone little by little.

- And you know, it'll leave an island of bone around the opening and usually by the time you get back to it, it's stopped.

- Okay. Here we're doing a craniotomy. Doodle was relatively easy to dissect away. Two bony cuts, one sort of coming around and stopping at the sigmoid, the lateral wall of the sigmoid sinus. And then we place it, place the drill again through the bone, back it out again, and then place it through the Burr hole for the second.

- Did you wire that back in place?

- We used a cranial fix, that has been very helpful and it's easy to use. We can wire it, obviously, you don't want to do anything on the area of the mastoid region, Peter,

- Yeah to make sure you don't violate mastoid air cells. How do you determine what is your extent of bony removal? Do you use less bony removal than what you see here, Peter? I use less, and once you get used to it, you get, you need the interoperative distance of 2.2 to see in the opening, so we'd like to have an opening that's a little over two centimeters. But the incision doesn't have to be quite so large. They do heal from side to side, not from end to end. And the important thing is to get that superolateral exposure as you, you're doing very nicely for five anterolateral for seven, and then in the middle for eight there. And, and then anterolateral, of course, for decompression nine, 10.

- How do you replace, do you do mosaic-like cranioplasty? How do you replace the defect?

- I used a titanium mesh and screw it in. It takes a couple of minutes.

- Okay.

- Unless the opening is too big, it works beautifully. But it will sink a little bit if the opening too big.

- Okay.

- And we also use this other, faster material that we've had a tendency to crack, that generally works very well.

- Thank you.

- Sure, this is the dural opening, Peter We used a nerve groove, I'll say groove director, and a 15-blade knife. You leave a sliver of dura between the sinus, and then this really keeps the dura over the cerebellum underneath the cotton rod. And therefore you will be able to, really protect it from the heat of the microscope. If you really reflect it like it's over the edge of the bone here, you're gonna sort of cook the dura and shrink it. Also, it's important to drill the superior cortex of the mastoid bone, to be able to have this stitch sort of lie around it nicely. If the edge is not drilled away, often, it just hangs over it and may impede the view of the surgeon. Only three stitches, one over sigmoid, one over the junction and one over the transverse sinus...

- Let's be very careful not to leave a little cup by the sinus, that's really important because you want to sew it back up. You put a piece of a strip of gel foam under it, with a suture beyond each end a running lock and suture that meet each other, then let a gel foam over it generally.

- Thank you. So that's the exposure sorta, we try to reach, and then, here is your nuance, so important. Use a rubber dam, a piece of glove, that's cut to the size of the cotton rod.

- Go ahead, Peter

- Usually shorten it then we put a picture in it to hold it. You can slide this on tissue, it doesn't stick. And it really makes a lot of difference as far as, may give you a rhythm when you're operating and not hurting the cerebellum. Sometimes we'll fold it back and push it over on a gel to get it to the corner there.

- Yes.

- works very nicely

- Now you can see sometimes in a retracting cerebellum, there could be a small venous attachment between the venous, I'm sorry, between the petrous bone and the cerebellum. And the surgeon has to be sort of taking his time or her time and making sure that the cerebellum is not retracted and too strongly... This is again, retracting the cerebellums gliding the cotton rod over the rubber dam, identifying the tentorium, petrous bone, their junction, and then staying on the petrous side, keeping this junction in view, and then identifying the cerebellopontine angle and the cisterns. And again, you can see the lumbar puncture that was performed at the initial part of the operation provides this very relaxed environment. Again, a relaxed surgeon, a relaxed brain leads to a relaxed surgeon, and we find that very useful.

- All right, yeah, older people, I think that that's necessary, it's helpful, I think in the young ones, 'cause you have a full...

- Okay, so you don't routinely do the lumbar puncture.

- No we don't.

- You may never do it at all. Only if you feel very strongly, that the tension could be very high.

- Exactly.

- Again, at this juncture, we try to slide the cotton rod over the rubber dam. Look first, use the tip of the micro scissors as a dissector Do not cut blindly, especially if the lighting is not perfect. You may cut some arterial branch that's embedded in the vascular tear. The sector may be very useful. Again, the tip of the scissors, going back and forth, dissecting the strands of the arachnoid, as you will see in a second, before cutting them would keep the deeper structures out of harm's way. You can see a touch of the seven and eight that will be left intact, we do not open the arachnoid over them.

- Sometimes we've found that retracting over five can tug on what was intact the arachnoid down there tug on seven, eight a little bit interfering with the brainstem auditory, but potentially, so sometimes we do have to open that arachnoid.

- Okay, Yes...

- But usually you're right.

- So one of the main reasons, if you have a change in your intraoperative monitoring and here, you can see that retractor coming in and exposing the roots... So if you have a change in your intraoperative monitoring in your eight, monitoring, you go ahead you're there, you go ahead and sort of look, make sure there's no tugging by the arachnoid

- What if there's an artery being pulled into it or pulled over the nerves

- Okay, so compression on a artery which would compromise the vascular tear to those nerves.

- Exactly

- Thank you. This is a left sided, retromastoid approach, Peter, and you can see the left sided trigeminal nerve. And initially we thought only the vein was compressive, but as you can see, we mobilized the root, the motor roots. And there is an artery right hiding underneath all of that in the axilla.

- Very good point, and that those motor branches can be inadvertently pushed up against the vessel rather than moved away from them. So you're looking around very carefully, very important, then you get constant burning pain, even the tic-like pain will be gone.

- Thank you, so as you can see, it is just way underneath. There's usually a vein here, the rootlets are covering it. And unless you push the nerve elevating inferiorly, you dissect these rootlets, it's really going to be difficult to find it. An inexperienced surgeon may just look and say, "Well, this, maybe this is a nerve, this is the artery, I'm all done." But really actually, getting between these nerves, the portio minor, the motor roots and portio major, the sensory root. And as you can see here, I'm trying to dissect it too as micro surgically as I can. And ultimately you can see pons more medially, and that assures that the decompression and mobilization has been adequate.

- That's important

- In the other nuances, Peter, at this juncture, in terms of improving and finding overlooking vessels, how can we...

- ...Bronchial arterior compression, you have the crushing vein laterally. and I can't tell, with 2D, whether that the caudal distal artery, it looks like ica has anything to do with the nerve there.

- Sure Yeah, you can see, I'm trying to push the Teflon in this tiny working space between the motor and sensory root.

- And you've got all the motor roots down.

- Yes.

- And you've got the artery going into a horizontal position and you will move the felt out to Meckel's cave to make sure you don't have distal compression.

- Thank you. And as you can see that actually, the motor roots were moved up here in this position and we make sure this is mobilized more immediately, so the nerve is not under much deviation and sort of traction. This is a second case where this is a left, I'm sorry, this is the same case, We're looking under the nerve to assure and make sure these two are also decompressed. Additional pieces of Teflon is placed to assure the inferior vasculature, including that vein and artery are not causing a conflict.

- It is critical

- As you can see how that shredded Teflon, Peter, just, as you very well mentioned, assures that you just do what you need. This is a left sided MVD, another case showing how the vessels can be impressive, a left trigeminal nerve, petrous bone, the lower vein, and as you will see in a second, when we mobilize this vein, you're going to see an impressive discoloration on the nerve by the vein. More immediately, the pause, I'm showing there's no compression more superiorly. And then as we lift up the vein, you can see this discoloration on the nerve, and then again, pawns, an ample amount of Teflon is going to be placed between the veins and the artery. Again, this is a classic example of venous compression. You agree, Peter?

- Yes, that's very good. That's very good. And you never know how much the gray is, is actually abnormality in myelin or what have you, and how much is in the shadows. If you bring it up, you can tell for sure. I think you have enough light there, but it's really gray.

- Thank you. And then you can see the amount of Teflon we put between the superior vein and the nerve, that has been sandwiched between the inferior and superior Teflon pieces. Again, the vein in the middle is superior Teflon and inferior Teflon, and showing...

- ...does the decompression with a lot of felt, but he's got the veins open.

- Yes, thank you. This is a left side of retromastoid Again, showing that there was really no compression. This is not in a 3D view so viewers and yourself may not be able to see, but this vein had no contact to the nerve. And since there was no contact, I proceeded with a rhizotomy using bipolars. And this was B2 and B3 and therefore, as you will see in a second, use bi-polar electrocoagulation to just gently coagulate the lower end of the nerve to complete a rhizotomy. This is that case Peter of the MRI, where giant ectatic basilar artery, you can see it has pushed the seven and eight in the location of the fifth nerve. Again, this is a right-sided MVD. Let me make sure you're oriented. And this is tentorium right there and the trigeminal nerve is almost at the level of the tentorium, very much pushed forward and the surgeon could be easily disoriented. And I think this is fifth nerve, actually it's seven and eight and if you're cutting the arachnoid, mobilizing this artery is really a daunting task and the surgeon should not persist as it could cause significant vascular injuries, this is highly vascular and atherosclerotic. What are your thoughts on these tough cases with large vessels, Peter?

- They are, they can be easier than you think, if you start by decompressing a weight from the point of maximum compression. Make sure you don't hurt perforators, go down here and decompress. Here are the hypoglossals, stretched over...

- ...I see seven and eight, yes

- I think it's the pike that's here, watch out for that. And the vessels, the big vessel can push a nerve into a vein or artery, so even though you move that, you got to be sure that you look at the other side of the nerve. Sometimes you can just sort of roll the nerve, nerve, which is badly stretched off that apex of the loop in a normal configuration map.

- Thank you, and as you can see here, my suction is pushing the artery as much as possible, again, the feel is the feel and practicing caution here is so important, pushing the artery and then lifting the nerve that is so thinned out and then using the dissector to perform a gentle rhizotomy, as you can see, and then placing as much as Teflon as you can. Again, you will see my suction is pulsating with the vessel here. I'm showing you how large and powerful the vessel is.

- I think there's a vessel on the rostral side of that nerve.

- Yes, and you will see in a second, we're gonna put Teflon all the way. Peter, very well mentioned by you from the all the way that we can see. And again, another piece, just like you mentioned, Peter, we gotta push things piece by piece and roll it toward the meckel's cave.

- That's a frightening artery, isn't it, with all that chalk in it.

- I know, it's sorta.

- It's going well, though, if you're gentle, slow and careful...

- And you can feel the pulsation in my, I can feel the pulsation in my right hand right now or at the time, so as they said, the pulse of the patient is in your hands.

- Right.

- So, I think that patient did very well and was very satisfied with the results.

- That's nice.

- Let's go ahead and review some of the pearls and pitfalls. And I would appreciate your thoughts, Peter, in this regard that controlling the bleeding with this, from the dural sinuses and sigmoid sinus with a little bit of bone wax to recreate the wall and sort of push in the hinge on the mastoid air cells to keep it in place may be more helpful than packing them and thrombosing the dural sinus. If you have a valve superior petrosal vein, and you have a lot of bleeding, first find the end of it on the cerebellum, coagulate it, and then use a little bit of gel foam over the small cotton rod and push the cotton rod against the opening. Using aggressive bipolaring only makes the opening of the superior petrosal vein over the petrous junction, bigger and more bleeding.

- Usually it usually bleeds at the junction of the vein and the dura. If you divide the vein, or if you don't divide the vein, you've got to cover the opening, and it's usually better. You may have to raise the head a bit to do this cause it...

- head of the bed, thank you, to prevent air embolism,

- Right The neurovascular conflict can be anywhere along the root entry zone and can extend into the nerve itself, so you have to see the entire root entry zone and the nerve 360 degrees, and gentle rhizotomies sometimes may help for the acute phase when we manipulate the nerve as an artery is decompressed until the nerve recovers from the chronic injury that has been caused to it by the vascular loop.

- That's sort of a philosophical difference because I don't like to manipulate the nerve, better that they're pain free, I got the vessel and if I have manipulated the nerve, I worry that I have missed a vessel.

- Sure, thank you. What would you say the most common overlooked sites for the young surgeons? Would you say it's the medial axilla of the root entry zone?

- I think it is, and the underside of the is probably second. Distal vein we've seen in our list of patients that we've operated upon, were done by other surgeons. A distal vein is often missed

- Thank you.

- The lateral rash of the at the root entry zone rostrally, you've got to see that, look under the because you have lifted it up. And if you go back under the nerve and then look the whole nerve and look distal.

- Okay The most, you know, often reasons for missing an arterial loop is the fact that the loop is covered by a motor rootlet or a vein along the axilla of the nerve more superiorly and discovering the discoloration along the nerve can be very satisfying and often confirmed that the surgeon has found what he or she needs to find. Again, this is an interoperative picture showing how the artery can be very much lying in the axilla the nerves purely underneath the motor rootlets that has to be dissected open, and the artery found and mobilized.

- Very good

- As you very well mentioned, Peter, the possibility of multiple offending vessels should be excluded with careful inspection. If you find one, it doesn't mean that you're done. Let's just get out of there, after, you know, you placed the implant. You've got to find secondary causes and also do not give up too early, and at the same time do not persevere two late, manipulating vessels too much, manipulating perforators can place the vascular to a significant risk.

- Very good points

- For a large artery embedded in the axilla, which is the most challenging sort of aspect of this operation, you may work superiorly and inferiorly and place the Teflon patch in order from above and below, and sort of meet, have them meet in the middle, or have a small piece of shredded Teflon, inserted from inferior aspect and then pushed superiorly in a semi-blinded fashion, again, not a completely blinded fashion and to be able to see and mobilize the artery and endoscopic techniques may be of great help in these situations.

- I used my antescope, that I really like, it's a little mirror, very small mirror I'm able to handle, and I can see around every corner I need to, I can't get pictures with it, but I can see what I need. I don't, I think the antescope is wonderful, except frontally, I don't think it matters very much in the cerebellopontine angle, but there are those who differ, that's fine.

- Thank you.

- And this is a picture you can see from a left vertical mastoid showing that artery that comes from here goes all the way up, really mobilizing, it's really difficult because it's not a vascular loop that goes like this. It's just straight in the depth of axilla. And this is a situation where you can place a Teflon, medially mobilize the artery and from the above, do the same, and it does cause that, you know, deviation of the nerve, but I really don't have any good solution. Do you have any thoughts in these situations, Peter?

- You got to have enough felt because you still got the outside of the loop there, the artery, one wonders whether it's a persistent trigeminal artery, you want to review your angiogram and this might be an indication for the old selective section, that Dandy Stripe published in about 1925, having some portio major on the plane of the pons, not getting the middle vessel, the intermediate vessel.

- Okay, so are you saying, What's that?

- It's hard to want to do that.

- I know, it is very hard, Peter. So would you say if you have an artery that it's almost impossible to mobilize, you think about, you know, a partial sectioning rather than mobilizing the artery?

- I do, well if you put the felt under the artery first, rostrally and caudally,

- Yes.

- Sometimes it will change its configuration enough, such that you can then get the pressure off the nerve and place more felt in between the two prior.

- Okay, I see.

- This is the way I would have handled this.

- Thank you And again, pitfalls of MVD, avoid cerebellar retraction - drain CSF, try to prevent sacrificing any veins. Remember the arteries are within arachnoid membranes, it's really tempting to just use the micro scissors without knowing where their tips are, where the tips are, exactly. And if you open the posterior fossa and the anatomy just doesn't look right, I think it's best to stop and revisit bone removal. Make sure you have the transverse sigmoid junction exposed. Find the petrous tentorial junction and keep that in mind. If you end up too superiorly as you're retracting the cerebellum, you will be over the cerebellum you're going to be retracting against the bridging veins to the tentorium, and you're going to have bleeding from the veins. And if you're too inferior, you're going to retract the cerebellum too much laterally and cause deafness. Therefore it is important to orient yourself carefully. The most, the first cause of inadequate decompression is inadequate exposure.

- Yes

- Do you agree, placing the retractors wisely, it is so important. It's just a couple of millimeters up and down could make a big difference in terms of your exposure, if your retractor is not right.

- I might comment on the vein situation, the veins we don't want to take, are those that are compressing a nerve, on the surface they're subpial of the pons. They've recollateralized, they have some growth factor we should be studying And it's early, it can be as early as a month after the procedure. The larger bridging veins, if they're not, if they're more than half the size of the trigeminal nerve just I tried to preserve this. As long as you preserve the don't injure, the transcortical relation to the cerebellum, you can take veins.

- Thank you. And one thing that many people have advised is that, I'm not sure how much I agree if a surgeon finishes the operation, doesn't do the compression and believes that, "well, I didn't want to retract the brainstem or cerebellum, it was too tight and because I want it to be safe, I didn't decompress the nerve adequately." I just have never had a problem. If you open up widely, the arachnoids, you place the retractor wisely, you should be able to expose a root entry zone at 360 degree of the nerve, pretty much in most cases. Do you agree with that, Peter?

- I agree, I agree.

- If there is a venous compression that is not very convincing and you may not find a compression lesion, I guess you can do a rhizotomy and that's using squeezing with the forceps, gentle bipolar coagulation at the root entry zone inferiorly, depends B2 and B3. We're just trying to partial section the nerve as much as possible to avoid disabling anesthesia De La Rosa the fashion, may be an approach, So if you, in a very rare case, Peter, you don't find any vessel, around the nerve?

- I look again.

- You look again?

- I want to make sure those common things, I took a bridging vein on the way in, that was causing the trouble. As a physician I've demonstrated this a number of times now. If we're operating upon the patient is to one way there, they are least likely to have pain. These vessels can move differentially off, off the nerves. So I think in the region might be an immediate push arterior loop back into the nerve, especially if it's the right type of pathological correlation, and veins are very frequent, especially in young women. And you must remember that, veins pulsate, they are intact.

- Thank you. Overzealous use of Teflon should also be avoided as Teflon granuloma has been rarely reported as the cause of pain recurrence. The compression of the wrong nerve has been also reported and obviously not acceptable.

- I've seen a number of these, it's a shame.

- Yes, and irrigate after you have placed your Teflon irrigate, make sure the Teflon does not get displaced by the flow of fluid. And again, wax in, wax out. This is a video, again, a picture of a big Teflon granuloma that I did recently, was previously operated on and in an outside institution, had recurrence of pain. And we identified this huge piece of Teflon and again, showing the nerve and the monitored decompression and deviation of the nerve. And after the Teflon was removed micro surgically, you can see the nerve looking much healthier in a more anatomical location. Let's talk about some controversial issues. Do you recommend intraop monitoring for every case?

- I do, a couple reasons. One is I'm training residents

- Yes

- and they have to start somewhere and they've got to know what they can do that will and will not hurt people, keep them gentle. Secondly, every once in a while I have a little change that I don't expect, I like to have it there. And if the people aren't monitoring this all the time, they're not as, as...

- How about perioperative steroids, Peter?

- I don't knowingly use them, although they slipped a few in occasionally because we had delayed headaches, Don Marion did that paper a long time ago.

- So you don't routinely advise using steroids?

- That's right.

- Even for that decreased risk of a septic meningitis with steroids, that doesn't really necessarily convince you that you have to use steroids in everything.

- What it does is delay it, and our delayed headache situation has gone way down and we don't know why, something's different. So maybe the small opening, we were operating more rapidly, losing less sleep perhaps, but we don't have the headaches that we used to have in the first two days a week.

- Sure, and how do you taper your pain medications for the patients if they're pain free the day after surgery?

- If they are on Tegretol, that's the one I worry about most and related drugs. Cut the dose in half, and then taper that over a 10 day period, we had this girl that was really, they were frantic, agitated, out of it. And if you do this, you don't have withdrawal.

- Okay, so you really taper it slowly after a few days that they're pain free?

- Yes.

- And how about if they have a CSF leak, unfortunately, either from the wound or rhinorrhea, two or three days after surgery, do you go explore immediately or do you do lumbar drain?

- We'll do a lumbar drain for 48 hours. If that doesn't work, then rarely we'll go explore it.

- Explore it again?

- Yeah

- And most commonly obviously is from the mastoid air cells,

- Yes.

- How about if the patient has a recurrence of pain or the pain doesn't go away after surgery?

- It means I missed a blood vessel.

- So you go, if they have typical trigeminal neuralgia and they wake up with a pain or they have a pain recurrence?

- I'll give them overnight. They sometimes will have a storm of severe pain and then it goes away. If they're still that way, the next afternoon, the following day, they should be operated on and we'll find the vessel that we missed.

- Okay, and you do feel that redo operation a few years after the pain, after the first operation and the recurrence of the pain happens, what are your thoughts on that?

- It's almost always much easier on the patient. And since we've learned how to expose it and stay away from things, it's easier on us, it doesn't take long. They have a lot less post-op malaise. The only risk with trigeminal neuralgia is increased numbness after these, after, you know, straightforward procedure.

- Okay, Well, Peter, I want to thank you again. Apparently there is a new book that's coming out on your behalf, Trigeminal Neuralgia really summarizing your amazing experience. So we are very much looking forward to it. I personally am myself, but I want to really, again, your experience meant so much to our presentation and I appreciate again your time.

- Thank you. I want to congratulate you because you understand what's going on in this. If the next generation can do this well, then I've done my job, it's not a gimmick.

- I think you surely have, and we all do appreciate it.

- Thank you, thank you.

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