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Grand Rounds: Microvascular Decompression Surgery for Hemifacial Spasm

John Tew

March 15, 2011

Transcript

- Hello, ladies and gentlemen. My name is Aaron Cohen. Welcome to another session of the AANS Operative Grand Rounds which will discuss nuances of technique for microvascular decompression surgery for hemifacial spasm. Today, we are pleased to have with us Dr. John Tew from Mayfield Clinic who'll be our discussion. Thank you for joining us. John, thank you again for joining us today. I'm gonna go ahead and jump in and review some of the basic concepts regarding management of hemifacial spasm. Please feel free to jump in any time as you feel necessary and give us your thoughts as you see fit.

- Okay. Thanks, Aaron. Please go ahead.

- Thank you. This is the disclosures for the presenters today. None of which interferes with the contents of the presentation. This is the first picture of the patient with hemifacial spasm that we could find in the Harvey Cushing Brain Tumor Registry at Yale, and it really depicts the spasms on the right side of the face. Harvey Cushing was pinching the face of the patient to see if he can trigger some of the spasms. Hemifacial spasm is another cranial nerve hyperactivity disorder. Other ones that we have discussed previously are trigeminal neuralgia, geniculate neuralgia. It involves intermittent involuntary twitching of the ipsilateral muscles of the face. It's important to know that the spasms typically originate above the eye and then spread to the other muscles of the ipsilateral face, and these spasms may lead to tonic contractions. This is important for the diagnosis and differentiation of hemifacial spasms from other disorders that we're gonna mention momentarily. Rarely, the spasms may start in the buccal muscles and progress to the rest of the face. And extremely rarely, the disorder may be bilateral. As like any other neurological disorder, the exam is important. Ipsilateral facial weakness is the only finding and typically due to either Botox injection which is the first mode of therapy or the neuropathy of the nerve related to neurovascular conflict or muscle weakness related to continued spasms.

- Aaron, I find that many patients, particularly as the disease progresses, have spasms during the sleeping hours that awakened them and become increasingly more severe. One other indication of severity is the degree of involvement that becomes so retracted that it interferes with vision. People may even run into objects or have great deal of difficulty driving. So, everyone has a problem dealing with the social aspects of spasms because their colleagues and people who don't know them are frequently totally perplexed about what they mean and frequently, people who don't know them think that they're being flirted with 'cause they got a little twitch in the eye and think they are getting a wink.

- Yes, yes.

- So, they might get into trouble that way.

- Yeah, I can hear you. Any other pearls that you use for the diagnosis of this disorder?

- Well, I noticed that you said it may be bilateral but it's certainly rare. So you wanna be certain that you don't get involved in a person who has a psychological disorder or so-called blepharospasm that has been said by psychologists that you can tell degree of anxiety that a person has by how many times they blink per minute.

- Okay.

- So, it can be a psychological disorder. And of course, real hemifacial spasm is greatly exaggerated by social contact and conditions that cause anxiety.

- Thank you. Let's go ahead and see a patient with hemifacial spasm. This video has been obtained with the permission of the patient. You can see the left-sided spasms that's the leading to tonic contractions as you can see at this moment. Nuances of diagnosis involves really not mixing up the typical hemifacial spasm with other disorders that mimic neurovascular conflict related to hemifacial spasm as you just very well mentioned. Hemifacial spasm may be caused by Bell's palsy or trauma to the nerves such as history of acoustic neuroma surgery. And in that case, it's called postparalytic hemifacial spasm. Obviously, that disorder is not amenable to microvascular decompression. And as John, you just mentioned, is it should not be confused with essential blepharospasm, facial myokymia, certain tic disorders, and facial motor seizures. The pathogenesis is very complex and not very well known. However, at least two phenomena may be involved. One is the ephaptic transmission related to neurovascular conflict and at least some sort of neuronal reorganization in the motonucleus of the nerve that causes and generates hemifacial spasm.

- Is that what you mean by injury to the nerve or if it is in the nucleus, it may be seen in stroke or previous injuries to the nerve, synkinesis?

- I think so. However, this is sort of a process that also involves neurovascular conflict as at least either a primary reason or secondary way where the spasm start.

- What do you mean by ephaptic transmission?

- You know, my understanding has been is that the vessel changes the myelination of the nerves and the axons in a way that different axons that were previously not in contact are now in contact with each other. And that process leads into some form of hyperactivity of the nucleus, leading to the generation of spasms.

- So, it's a crosstalk or kind of like a local electrical discharge, somewhat like a mini seizure, if you will, in the nerve. So, there's a lot of analogy with an actual seizure disorder.

- Okay, thank you. So, what are the treatment options? Often, patients started with Botox injections. Peripheral rhizotomy is really not standard of practice anymore. However, the Botox injections cause cosmetic deformity. Their fix may go away and the spasms start every three months as the patient reaches the end of his or her cycle. And often, patients opt for a more definitive therapy, which is microvascular decompression using infra-floccular approach which we'll be discussing today.

- Don't Botox injections actually become less effective because many patients may become...

- Resistant.

- Develop antibodies to the Botox and also, it's kind of a paralyzing drug. Isn't it somewhat like doing a peripheral neurectomy or partially paralyzing the nerve?

- Yes.

- So, they work in the muscle?

- Correct, and then nerve endings.

- What about the question that's been asked, do repetitive Botox injections make the disease worse or make the surgical therapy more difficult and less effective? Do you have a feeling about that issue?

- No, I would like to know your opinion. I don't think the Botox necessarily affects recovery after microvascular decompression, except the fact that the face itself may take much longer and the Botox may injure the root endings of the nerve to the point that the facial muscle recovery may not be as adequate after microvascular decompression surgery.

- I think that's certainly true and also, the longer the disease is present, the more severe it becomes, the less effective an operation for decompression is likely to be and also the more likely you are to get a delayed response to effective decompression.

- Thank you. As you just discussed it, the cosmetic deformity, the need for injections, and really posterior fossa exploratory surgery remains the most definitive therapy. MRI and CT scan should be performed beforehand to rule out a vast and a structural abnormality. I have seen patients present solely with hemifacial spasm who had an epidermoid evidence on their MRI. So, we wanna make sure we rule those out, at least be prepared for it if we wanted to remove the tumor rather than just explore and find the tumor as a surprise. I would like to know your opinion. Even if patients have no evidence of a vascular loop on a detailed high resolution MRI, we still offer them an exploratory surgery because we have found some very large vessels. Not large, but there's some vessels at the root end position of the nerve that were not evident at all on detailed MRI evaluation. What are your thoughts, John?

- Well, we always... If you just have a routine MRI, I'd ask the patient to have a FIESTA protocol, which is very effective at showing up the blood vessels and refocus it around the posterior fossa. And I'd say 90 plus percent of the time you'll see a contact point with either a major artery or certainly a major tributary.

- Okay.

- I'm hesitant to operate it if there is absolutely nothing, but patients may want to proceed anyway. I think the more common situation is the person who doesn't have the problem quite bad enough or maybe it's relatively minor and you wanna wait a while before deciding to do it.

- Okay.

- In that circumstance you wanna be absolutely sure that you're not overlooking a significant problem and need to do early surgery.

- Right. Obviously, you don't wanna do surgery on patients who suffer acutely from hemifacial spasm. At least a certain period of time is required to make sure the patient is suffering from a neurovascular conflict. And how young that the patient can present with primary or neurovascular hemifacial spasm?

- I think the youngest patient I've seen is in their early 20s.

- And you were able to find the vessel during exploration?

- Yes.

- Okay, thank you.

- The disease is certainly much more common in certain nationalities. I'm not quite sure why, but that's... Our colleagues in Asia have a much higher operative experience than we do because it's much more common in the asian population.

- Thank you. This is an MRI of axial MRI T2 showing the vessel compressing the root exit zone of the right facial nerve. That tends to be the typical findings. This is another MRI, a more compressive or a more impressive branch of the vertebral artery. Thank you, John. These are some of the SPACE/FIESTA sequences showing the artery compressing at the root exit zone of the nerve. This is a sagittal image showing the vessel as was the nerve exit zone from the brainstem. What are the indications? Patient preference, failure of Botox injections, as John mentioned, interference with binocular vision. And obviously, the patient has to be young and can tolerate surgery and the patient should be warned about the risk of hearing loss after surgery as that's one of the serious risks of microvascular decompression surgery for hemifacial spasm. What are your indications if I may please ask?

- As you said, the patient should be young but you have on there physiologic young. Would you do one of these operations on me or you mean somebody who's 30 years old? What is physiologic young? What do you mean by that?

- Physiologically young. I have done this procedure on 78 year old man who's been healthy and physically fit as you are. And so, I think physiologically young can be up to 80 years old. What are your thoughts on that topic?

- I don't know if I'd put a chronologic age on it. I think you and I were talking about this recently. I saw a 78 year old patient this past week who had a spasm. He wanted to have it repaired and I tried to convince him I didn't think it was severe enough because he had some other vasculopathy that I thought his risk would be too high to justify it. So, he went home to think about it for a while. So, being physiologically young excludes vasculopathy in my view because that's probably one of the highest risk.

- Okay. But you would offer it to a 78 year old man who is medically fit for surgery if they are suffering from significant amount of spasms?

- Well, I wouldn't withhold it. I wouldn't withhold it from that person.

- Thank you. Intraoperative monitoring is a controversial issue and there's really no class one data. However, especially for the novice surgeon, monitoring the BAERS and the eighth cranial nerve is important to monitor amount of retraction and injury that could be placing the eighth nerve at risk. The lateral spread reflex, LSR, is a very useful tool. And what is really LSR? It's a measure of hyperactivity of the facial nucleus. We stimulate two branches of the facial nerve and record from a muscle of the face that is innervated by another branch. And that's called the lateral spread reflex and, this again, a measure of hyperactivity of the nucleus and often when you mobilized the artery in this surgery and that goes away, it really gives you a good feeling that you have found the pathology and you have handled it a proper cu- Although, patients who have their LSR disappear with mobilization of the artery may not at all times be free of the spasms when they wake up. So, the sensitivity and specificity is not very high. However, it's a very useful tool. Do you use LSR and BAERS during surgery, John?

- Well, we do them. I'm not sure that I use it. I think it's important to as you spoke about that. Sergendo is doing this in his early career or experience just to be sure that he is operating on the facial nerve, and you do that of course by stimulating it. Many circumstances, you'll see hyperactivity without stimulation. The patient will have spontaneous firing of the motor neurons just on exploration. It is a seizure-like disorder and you're always comforted when you see that disappear when you take away the compressing element. Of course, I do use it for one other reason. As we have mentioned before, if you're operating on a person who's extremely nervous and you don't wanna let them wake up with continued spasm, it might be wise to struck the nerve a little bit or even compress it with delicate forceps before terminating the procedure even after you've done an effective, careful decompression particularly if the nerve is still hyperactive at the conclusion of the decompression.

- So if I can hear you correctly, you use number one, for identification of the nerve if it's not very clear and number two, for a very gentle rhizotomy of the nerve if you don't find a vessel and if the patient is very nervous and definitely would like to have some sort of relief even if it means a little bit extra weakness in the face.

- Well, I wouldn't use the term rhizotomy. I would use the term neuro practice. Short term period of neuro practice.

- Sure.

- In that, many patients will have... After you to do an effective decompression, for a few days or sometimes even a week or two, they'll have continued periodic spasms, maybe even at night. So, you don't wanna have that particularly in a person with whom you wanna have excellent rapport immediately after surgery. So, better to just cause a little mild neuro practice in the nerve for a few days by quiet, careful compression of the nerve with a pair of forceps.

- Thank you. Let's review on animation just to briefly see what the surgery involves. This is a right-sided retromastoid approach. Again, going around the cerebellum. These are the basic concepts. Gently retracting the cerebellum, finding the seven and eight. Again, retracting more superior medially rather than purely laterally as you can see in this video. And placing a Teflon patch between the nerve and the vascular complex.

- I may make a suggestion, that point. Can you bring that one back just a moment?

- Sure.

- Is that possible?

- I'm happy to. Let me know when you would like it to be stopped.

- Rather than-

- I'm sorry, let me go back.

- If you said superior medial placement of your retractor, I might put the retractor a little bit lower down here to elevate the flocculus, then retracting the flocculus medially.

- Okay.

- With the retractor about here, just in that space, just infra or below the flocculus and just at the upper edge of the ninth nerve.

- Okay.

- So that you're not retracting the flocculus medially and not putting any pressure on seven and eight.

- Okay. So, essentially you're gonna follow the ninth nerve and move the retractor parallel to the ninth nerve and inferior to the flocculus in order to see the root exit zone of the nerve.

- Right.

- Yeah, that's a very important nuance that has worked very well. I appreciate it. So, this is a basic operating room set-up. I think that, John, you have the anesthesiologist placed at the foot the table and that may improve the space for the surgeon and the assistants to work on the head. And what we have found useful is to place the surgeon across the table from the assistant to make the transfer of instruments relatively seamless.

- Yeah, I get along a lot better with the anesthesiologists at the foot of the table. So, if he goes to sleep it doesn't bother me.

- Thank you. We have come to like the lateral position and we do a lumbar puncture before proceeding with the craniotomy just because it relaxes the posterior fossa, the dura. It may even decrease venous bleeding, and going around the cerebellum is a lot simpler as we'll see in a minute. We just sort of placed the needle as we go wash our hands. And as they're draping the patient, we moved the needle the last minute. We collect about 30 CC. And we obviously arrange the pressure points. In this illustration, I think we should remember not to put too much pressure on the head of fibula for the risk of neuropathy. John, do you do lumbar puncture or anything different for the positioning please?

- I did. But first, I'd say rather than a lateral position, I'd call it an oblique position because I put the patient into a more... Some people call it a park bench but I go with a lateral oblique. So, the patient is actually leaning forward. Yeah, that's right. It's an oblique position. So, with the padding underneath the axilla. And then we change the position of the patient quite a bit during the procedure, particularly to allow you to explore the nerve as you come around the edge of the cerebellum. Yes, I did do caps lumbar puncture early in my career 'cause I thought particularly in young patients who had a very full cerebellum that it helped. I don't do it anymore and we can talk about the tactic that we use today that helps to get the CSF out.

- Okay, thank you. One thing that you mentioned very well is this sort of oblique position allows the shoulder to fall away. Especially in large patients, that makes a very, very big difference because it opens the angle... Not opens the angle, it moves the shoulder to the front and that provides an increased space to work on this area without having this shoulder right here sort of being the working zone on the surgeon.

- Also, you could put a piece of tape on the shoulder and pull it down so it's... You do in a large patient like the one seen here on the right. It helps to get that shoulder out of the position of your approach.

- Thank you. We have come to like the curvilinear incision as was advised by you. I remember you talked to me about this during one of the meetings and it's really has worked beautifully. It has advantages and please let me know if I miss any of those advantages. Number one, it avoids the neurovascular bundles. Number two, it keeps the flap inferiorly as we'll see in the next illustration. But before we go on let me- The position of this flap is just along the transfer sinus. The transfer sinus is defined by a line from the inion to the roots of the zygoma, and the sigmoid sinus is anterior just to the mastoid groove. And we try to knowing that those landmarks and the fact that the line of the mastoid groove which crosses this inion root of zygoma line is where the junction is located. That would be in the summit of this incision. And here is, in the real patient image, the tip of the mastoid, the location of the incision, and the location of the transfer sinus by the dotted lines and the mastoid groove by the other dotted lines. In the cross section, this is a linear incision. This is the cerebellum obviously and this is sigmoid sinus. As you retract the muscle and scalp flap, this often bunches up. Again, this is a linear incision. And under the retractor, it increases the working distance as evidenced by the length of the retractor all the way to the brainstem. However, if you look at a cross section for a curvilinear incision, the flap reflects inferiorly and that really prevents that bunching up under the retractor and the working distance is much less. Any other advantages, John, to this curvilinear incision?

- Well, I did the curvilinear incision change probably 15 years ago for two reasons. One is that Sonny Danny did it which is pretty hard to improve on many of the things that he did as a great surgeon. Secondly, patients complain about pain if you go into the muscle of the midline. And frequently, at least maybe one or two times out of a hundred, you get into the nerve, particularly the nerve bundle, and the patient gets a postoperative neuralgia or neuropathy. And they don't like that. It's one of the common complaints of the so-called retromastoid approach if you look at several hundred patients who had acoustic neuroma. So, we're trying to avoid the pain by staying out of the muscle, secondly by staying out of the neurovascular bundle, and thirdly, as you point out, to get the muscle flap out of the way so it reduces your distance to the operative trajectory.

- Thank you. This is the quarters we use, again, along the ninth nerve inferomedial, just beneath the flocculus. It is quite different than more of a superior approach that used for trigeminal neuralgia.

- We call it, on the left side, seven.

- Uh-hmm.

- Three.

- Yes.

- Four and five and eleven.

- Okay.

- You position your retractor depending on your trajectory as you go around the edge of the cerebellum.

- Thank you. This is a short video of really showing some of the disadvantages that I have faced in terms of using the linear incision. As you can see, this bunching of the material, John, underneath the retractor using a linear incision increases this working distance going through the cerebellum and that's really led us to completely convert for acoustics or any retromastoid approach. We have liked this skin incision and has had major advantages.

- Well, you have to make a much longer incision unless you know exactly where your craniectomy or your craniotomy is going to be with a linear incision because you have to get that material out of the way. You have to so that you could get your retractor away from the edge of the flap. Whereas here, you see it's taken down and it's completely out of your way.

- Right, you can see the craniotomy space or the bone unhindered by any of the scalp flap. Again, to place the initial burr hole, we try to identify or assume where the junction is using inion and root of zygoma and the mastoid groove. Junction for the inion-root of zygoma line as well as another line which is vertical from the mastoid groove. The intersection would be the transfer sigmoid junction. We placed the burr hole just a little bit inferior to that. And for novice surgeon, you may wanna identify the junction just inferior edge and then extend your craniotomy or craniectomy inferiorly. We have come to use craniotomy after we have found the inferior edge of the junction. And again, the bone removal is more inferior than the usual trigeminal neuralgia. John, may I ask? Do you do craniotomy-craniectomy, or how do you start your bone removal?

- Well, I'll just point out a couple of things here. You're using a retractor. I don't use retractors anymore. I use a... It's like a fish hook but they are made commercially. I think you call them Lone Stars or Alamo or Texas or whatever, but it's just a big fish hook. It goes in here and you attach it to the drape and so it moves all of this bulk of a retractor out of the field and it gives you a lot more space. To answer your second question is I just put a burr hole and it's covered by a 25 millimeter burr hole cover. So, I don't save the bone. I don't save the bone dust. And one of the reasons for that, you see the sinus here?

- Uh-huh.

- See the sinus?

- Yes, uh-huh. Yes.

- You don't know exactly where that sinus is. You may damage it with the drill while you're turning a flap. So, we just use the burr and make a small craniectomy, 25 millimeters in size. And of course, this is a craniotomy here for the trigeminal exposure. Below this point, it would begin at the lower end of this craniotomy. That is for exploration of the seventh.

- Okay. So, where would you put your burr hole in this illustration? If you could please show me.

- Right here where the red dot is.

- Okay, so you start very medial almost and then you extend your boney removal until you identify the sigmoid sinus?

- Edge of the sinus.

- Okay, I see what you're saying.

- And here, we wouldn't be looking to expose the transverse edge but just the medial edge of the sigmoid.

- Okay, so your initial burr hole essentially is just a little bit more medial than the sigmoid notch and then extended until you see the very small edge of the sigmoid sinus.

- And then you've come medial enough to give you the exposure which you would need, about 25 millimeters.

- Thank you. That was very useful. Again, the bony removal-

- I'm just saying one more point. I don't think the early experience should be confined to 25 millimeters because it's of course, more difficult to operate through a very small cranial opening and they don't give you any prizes for doing that. You don't get any special ribbons for operating through an extremely small hole.

- Sure, thank you. Again, the boney removal as you mentioned, is extended to the edge of the sinus using a drill. The mastoid, you may you use a Kerrison with the mouth of Kerrison pointing upward in order to avoid any injury to the sinus. The mastoid air cells should be very well waxed. The dural opening starts along the sinus and then extends more along the floor. The trigeminal opening is onto the other sort of end of the curvature. It starts sigmoid and goes along the transfer sinus. This starts along the sigmoid and goes along the floor of the posterior fossa. This is what, John, you were mentioning about the fact that just the edge of the sinus is exposed, is reflected superiorly. And then, we go ahead and find the petrous bone. As you can see here, as it curves around to become the floor and lift up the cerebellum superiorly and medially in order to identify the lower cranial nerves.

- Let me make a couple of points here. I've spent more time watching people trying to close the dura watertight for the reason that you get too close to the bone edge or too close to the sinus. It's okay to leave five or six millimeters of dura here, beginning to reflect it up as you've done so beautifully here, and it makes a lot of difference when you're trying to close. So, you have an adequate dural edge to suture to. And we'll say something else when we get talking about closure but in the opening, don't cut too close to the bone or too close to the sinus because one, you don't wanna open the sinus and two, you wanna have enough dura to close easily.

- Thank you. The arachnid over and the lower cranial is open. As you can see that a vector of retraction, John, is parallel to the ninth nerve as was very well mentioned by the nuance you thought about previously. And the tip of the scissors has to be always in view because some of the vessels may be entangled. The arachnoid over the lower end of the seven and eighth cranial nerve has to be opened in order to prevent any traction on the eighth nerve causing potentially changing the BAERS, and you can see in the cross section using micro scissors and sharp dissection. You lift up on the flocculus as you can see right here. The exposure is right parallel to the ninth nerve, lifting up on the flocculus. We're not retracting parallel to the seven and eighth nerve, and right here you will see the exit zone of the nerve. You may elevate, I guess, the eighth nerve and see even better where the root exit zone leads to the trunk of the nerve and how the artery can be mobilized. And this is the discoloration at the root exit zone of the nerve. Go ahead John, please.

- Well, this is a very good point that you're making here now about your trajectory of exposure is inferior to the facial nerve and in order to get that exposure, we have to lyse the arachnoid over nine and over the inferior aspect of seven. I can remember just like yesterday, 43 years ago when I did the first one of these operations, I looked in and I looked down on top of the facial nerve and top of the eighth nerve retracting the flocculus and I didn't see any arteries. I'd never been taught how to do this procedure so I was teaching myself, and I was almost ready to close up and I said, "I think I better look underneath there" because I remember Dr. Janetta saying something about it being anterior to the nerve, and there it was. So, you're doing it just perfectly. You have very nice exposure and that's the major lesson to learn. Look underneath. Look at the root entry zone, anterior to the nerve.

- All right. The root exit zone of the nerve is really inferior to the whole seven and eighth complex.

- Right.

- And that key is so important that many people know. But I think for some reason, it just doesn't go through as you're exposing the surgical area. That even though the seven and eight is here, the root exit zone of the nerve is at the brainstem, almost half a centimeter more inferiorly where the discoloration and compression by this artery has occurred. Thank you, John. Again, the Teflon pads, even shredded or not shred. We shred a Teflon. John, I know you don't shred the Teflon. You cut it into small piece and sort of lodge it between the artery and the brainstem and the root exit zone of the nerve. I think those nuances is relatively surgeon dependent. And after the Teflon is padded, the shredded Teflon for us has worked because it lets us mold it a little bit better in small pieces. But again, that's just one way to do it. It's not the only way. And again, as you can see, this artery was well padded by the Teflon patch away from the seven and eight cranial nerve complex. This view again shows the intense amount of discoloration caused by the arterial loop against the nerve and finding this as the LSR disappears really gives you such a good feeling that you handled the pathology well and you are ready to be happy with how the case has gone. Let's go ahead and review some of the surgical videos and I appreciate your nuances in terms of how the procedure should be conducted. This is, John, a left-sided retromastoid craniotomy. Please feel free to use your blue arrow. As you can see, the dura, the edge of the dura, has been tacked up the petrous bone and the floor of the posterior fossa refracting the cerebellum parallel to the lower cranial nerves rather than parallel to the seven and eight complex. Go ahead, please.

- Well, you're asking me for suggestions here. I like the the exposure. One of the things that I would do early on and you probably have done it here, rather than removing CSF with a spinal needle, I just slip down here with a Penfield 3 and put it in with the concave side up, push the cerebellum down, and use an arachnoid knife and nick the arachnoid of the cisterna magna. So, that immediately lets the CSF out. You've done that by your needle in the back and then lyse this arachnoid with the same knife. The other little nuance I do is I don't use this padding 'cause it takes up room. So as soon as I take out the Penfield 3, which is placed right down here to kind of depress the cerebellum a little bit. I actually do that before I bring the microscope in.

- Yes.

- And then bring a microscope in and put the one quarter inch retractor right here. That way you have your suction. I just let that rest there to kinda protect the cerebellum. I noticed you have a rubber dam covering the cerebellum, but that's really all you need. You just strip your retractor. I use a self-retaining retractor that attaches to the head holder or head frame and it fits just perfectly right in there. It said, "Retractor, if I may say so, I designed specifically for this purpose," and it works beautifully. But you're doing it just ideally here. I think if you don't use this cottonoid, you need a little bit less room and it will look just perfect just as you're doing it.

- Thank you. And as you can see, this is a right retromastoid approach. Let me correct myself. Just like what you mentioned, parallel to the ninth nerve, opening up the arachnoid membranes, not pushing pressure and retracting parallel to the seven and eight complex, and the pad is taking some space. I think that's a good nuance I should personally follow. And again, the ninth cranial nerve is being followed, lysing the arachnoid membranes parallel to the nerve. You can see again a radial loop, but the compression is not along the nerve. It's on the brain stem where it becomes the seventh cranial nerve. And therefore, the surgeon has to be patient. Open these arachnoid membranes and make sure adequate exposure of the brain stem and its confluence with the seventh nerve is evident. Thank you. Go ahead, please.

- So, identifying the flocculus here and you could see when the flocculus has to come upward.

- Yes, as I'm doing here-

- And your retractor just exactly in the right place. Now, you're seeing this probable branch or major branch of the ICA right up underneath the facial nerve.

- Right, and that's the facial nerve sort of moved. And as you can see, you need a good view of the brainstem. Go ahead, please. This is the discoloration you're showing at the tip of your arrow. Really impressive. You can see I elevated the eighth nerve without much difficulty and changing the BAERS which was very clearly showing the discoloration. Here, I believe I'm focusing more just showing the area of discoloration. It's just such a pretty anatomy, finding this discoloration along the nerve, and you can see how far the exit zone of the nerve is going and the coloring is so different here versus more anteriorly.

- It is white in the vestibular nuclear nerve and more gray-tan appearance in the facial nerve.

- I know you use a small piece of Teflon. I have come to use this. I'm not sure one has a great advantage over the other, as long as the nerve is very well petted away and there's no contact and the padding goes all the way more distally, not just in a small portion of the artery, to make sure there's no chance that the contact would reappear. Go ahead, please.

- I use a Teflon. I don't shred anything except the end that tucks up underneath the flocculus. I'll make a spear, kind of like a dental spear, if you know those things that the dentist use to clean your teeth with.

- Sure.

- You hold it with your retractor and you slip it down in front of the brainstem and the distal end of it is slightly spread apart so that it tucks right up underneath the flocculus.

- Okay.

- So in this case that you just showed, it would go right in here and then the distal end would feed right underneath the flocculus.

- So this is another case, John. A left side retromastoid approach. Let me make sure I orient you. And this is a nuance you talked to me about a while ago that the labyrinthine artery or the vessel that goes between the seventh and eighth complex is not typically the pathological entity and should not be manipulated. Again, this is a left-sided approach. This is the seven and eight. And as you can see, I'm trying to look around to see what's going on. And there is a vessel there deep on the brainstem, which obviously is not causing anything, and I'm just trying fishing for some compressive vessel. Don't see much up there. You can see this vessel there. And here when you lift up, this is not the artery between the seven and eight. Rather, this loop way tucked in underneath where the seventh nerve joins the brainstem. Again, you see this vessel between the seventh and eighth complex which is not the compressive lesion or rather the artery that was tucked in inferior to it. Go ahead, please.

- What is this artery here?

- You know, that artery was very superior and had no contact with-

- Here's the contact artery right here that you're separating away with your cushion.

- Correct But you see, we did not touch the artery that went between the seven and eight right there that is superior right now to my Teflon patch. So, I think that nuance I'm trying to point out here, and I appreciate your thought, is if there is an artery between seven and eight, it is not necessarily the pathological entity. You can see better here right now right between the seven and eight complex.

- I think if that's the only thing you find, you should put your pad out here but don't place a pad between the seven and eight.

- Okay.

- That may interfere or cause spasm of labyrinthine artery and cause permanent or major hearing loss.

- Okay, this is another case, John, that I have faced personally and I don't know what the right answer is. This is an older gentleman who saw the MRI earlier in our session that had this large dialoctatic vessel. You can see here. This is the eighth nerve. The seventh nerve is pushed up superiorly over the artery and the anatomy is very confusing. And as you can see in this video, mobilizing this artery, unless we use the sling method and put a sling in a suture with a fiber around the artery and suture that to the dura, is almost impossible in any other way to mobilize this artery besides putting the patch. However, this vessel as you can see here, it's joining the larger vessel and mobilizing this with a fiber and a suture was not possible for us and I ended up padding it. What would you do in this situation?

- Yeah, is this the basilar?

- I think so.

- And this is the left vertebral, right vertebral?

- Correct.

- So, the option here is to put a sling around right here, tied up to the dura over here.

- Yes.

- Or separate this vertebral away from the facial, as you're doing, and put a pad there. This is one of the reasons I like the more solid Teflons. I would slide it in back here, further back adjacent to the brainstem.

- Okay.

- And you get that.

- In this situation-

- I'd try to put it in right about here.

- Okay.

- And if possible, if I didn't think that worked adequately, I'd put a sling around and then suture it up to the dura over here to try to pull it away.

- In this situation, the other vert was against the clivus and it was almost impossible for me to pull this one without causing some... Nothing would move because the other one was already against the clivus and it was holding this one in position. And unless I really start putting a lot of pressure on the suture, it would not do much work and I felt the risk of that was too high. I'm not sure if the video does justice more to showing... Again, you can see the left foot against the clivus, the right vert jammed against the root exit zone of the nerve. We pushed in more shredded Teflon inferiorly to make sure all is decompressed. But you think you would have been more aggressive in terms of mobilizing the artery?

- Well, I can't tell here. But it looks like right here, you might've been able to put a piece of Teflon right about there. It looks like that to me as I look at it here and I certainly understand why it would be hard for you to put a sling around it and pull it over to the side because there's already a big vert in your way.

- Right. Yeah, we tried the sling method and that did not work. As you can see, I eventually put more Teflon where you're talking about. I'm not sure if the piece of video we included mentions that. Here we go. I think that's what you were talking about, John. Is that correct?

- That's right. I would put that Teflon spear right in here and run it up underneath it.

- Right. And as you can see the artery pulsating so much.

- Take this pathway.

- Correct. Get more... In other words, more inferior toward the lower cranial nerves and try to see what you can find there. This is another video of a patient that, again, it's a right-sided retromastoid approach. This is the vessel between the seven and eight that we decided is not gonna be the pathological entity. This is the root exit zone of the facial nerve and there was really no compression. There was a vein on the brainstem and if there is a vein on the pier of the brainstem, we decided not to mess with that vein because that can have consequences of venous infarction. If the vessel is in the subarachnoid space and is compressive, one can coagulate and cut. But in this situation, John, you can see that root exit zone of the nerve is discolored. This vessel goes between the two. There is a vein on the brainstem. What would you do in this case? I'm doing a little bit of a gentle manipulation to cause that neuropraxia you mentioned.

- Cause a neuropraxia there. I would put a Teflon sponge down here into this space and then hook it right underneath there.

- Okay.

- I would not try to put it between seven and eight.

- Right, I think in this... I'm not sure if in 3D that's clear. That vessel was really in contact with more of the nerve distally, so I'd made a decision not to do anything and leave it as sort of a gentle neuropraxia. And the patient had a little bit of weakness, recovered from that. Actually, the weakness may be about the same just slightly impulse than before surgery and recovered from that shortly and has been spasm free. Although, I'm not sure how long that would last. So, let's go ahead and-

- I learned that from experience. You know, good judgment comes from experience and experience comes from bad judgment. So, I've had a lot of bad judgment in the past. So, I know not to manipulate that labyrinthine artery too much.

- I think-

- You may get a very good result from the tactic that you just showed there.

- Thank you. This is a postoperative CT scan. Typically, patient shows the Teflon patch in place. You have reported your series and I really liked that nuance that if the patients are spasm free for the first two years, the chance of recurrence is really small, and that's good for patient counseling. Janetta reports 84% excellent results and 7% partial success at 10 years. So, this is an operation that works. Doesn't work all the time, but it does good work. What are the complications? And again, the deafness is a real concern that has to be discussed. If you're retracting the cerebellum, you have to be careful about that. Severe facial weakness, operative death, and brainstem infarctions are really extremely rare in this operation, especially in experienced hands. What are your comments, John, in terms of complications that we could avoid and any other details relevant?

- Well, by far the most common complication you haven't listed there and that's CSF leak or pseudomeningocele. Infection should be less than 1%. So, some people have a pretty high incidence of CSF leak but that should really not occur and we'll talk when you get to the closure, if you show the closure, how to prevent that.

- Okay, if we may go ahead and talk since we're talking about it, I think you mentioned that you close the dura with a piece of muscle, that you go from inside to outside. In other words, you trough the muscle from inside to outside. You assure a watertight closure. Your mastoid air cells are well waxed. You put a titanium plate. And then before that, you also put some glue on epidural space in order to assure maximum and a watertight closure. Is that correct?

- Yeah, we use a biological glue on top of the dura and the dura is closed by putting a graft inside and then suturing it. So, when the CSF comes up against the graft, it forces it to closure. So, you have a very low risk of leaking. And of course, waxing the mastoid air cells, you're not gonna have a rhinorrhea.

- Okay.

- So, also this closure that you showed, the oblique or curvilinear incision, closes very well with a good muscle cuff.

- Thank you. This is the section of the session I really would like your opinions in terms of what are the perils. I think if you're a novice surgeon, eighth nerve monitoring is good. Lateral spread reflux response monitoring is good. Untether the lower cranial nerves well. Be patient. Don't retract the cerebellum aggressively. Retract parallel to the ninth nerve. That's critical to avoid damage to other structures. Place the retractors judiciously. Address changes in the BAERS by repositioning the retractor. Prevent vascular compromise under the retractor. Release the eighth nerve. And sometimes, just maybe increasing the blood pressure, giving it some time for the brain to adjust before you replace the retractors may work. What are other details and nuances if you have a change in BAERS that you may need to address, John?

- Well, I think the most important thing here is to get good relaxation of the cerebellum before you approach the brainstem or the cranial nerve, and you do it by removing CSF. I do it by removing CSF inside the cranium by opening the cisterna magna. So, retraction is not needed. Really, you're putting the retractor there to protect the cerebellum and just to point your action to the flocculus and to allow you to release the cranial nerves so that you can maintain the cerebellum in its position until you get to the brainstem.

- So in other words, the retractors are all really not retractors. They're holders.

- Yeah, they are kinda holding the position as you do your dissection with two hands. You use your suction as a retractor for the final spot and then either scissors or arachnoid knife for the second part. So, you wanna have two hands used at all times. And I don't rely on the monitoring at all because really if you get problems with the monitoring, something's already happened. You wanna prevent anything from happening by your very careful technique and this exposure that you nicely outlined here.

- Thank you. As you well mentioned, the seventh nerve is usually gray. It's posterolateral and auditory is yellowish-white. I'm sorry, the seventh nerve is anteromedial, it's gray. And the posterolateral auditory nerve is more yellowish. Obviously, you don't wanna decompress the wrong nerve. The conflict is that along the brain stem at the root exit zone of the seventh nerve. It is not on the trunk of the seventh nerve in the cisterns. And the detailed inspection is important. Gentle handling of the seventh nerve is critical and gentle neuropraxia of the nerve may be helpful if you don't find a pathology as you well discussed before, John. Retract along the ninth nerve. Don't retract purely laterally. Overlooked sites are usually the medial axilla of the root exit zone of the nerve. It can be covered by a vein, by arachnoid, embedded in the brainstem underneath the flocculus. That's the most common site where the surgeon does not find the artery. And just to say that I've heard people say, "Well, I didn't wanna place the patient at risk by a lot of retraction. Therefore, I didn't think it was safe to really inspect things. I just closed." I just don't feel that is a reasonable explanation. Do you agree? I think with appropriate microsurgical techniques, we should be able to expose this area relatively safely almost in every case. Is that correct, John?

- Oh, I think most of the problems are failure to position the patient appropriately, failure to get adequate relaxation of the cerebellum.

- Okay, thank you. And again, we talked about not playing with anything that's between the seventh and eighth cranial nerve. Multiple offending vessels should be excluded. Surgeon shouldn't give up too early and obviously, not to persevere too late. The perforators are very important. You don't wanna place the Teflon that would avulse a perforator. And there is atypical cases where the spasm starts more around the buccal muscles. And interestingly, those cases, the compression may be rostral to the nerve. And therefore, if there is an atypical feature to the spasms, a more rostral inspection of the nerve should be advocated. If the artery is large and embedded in the axilla, more and more proximally, as you well mentioned, John, and mobilize the artery. Avoid aggressive mobilization to place the patient at risk. This is a benign disorder. We don't wanna have a stroke that would cause significant morbidity. The sling method has to be used with caution. This is a method that does have significant complications if it is used aggressively to pull or push on arteries that have been in position for many years. And what are your thoughts about endoscopic techniques, John?

- Well, I think endoscopic techniques are something that we need to be exploring more, but you have to learn how to do this operation very well before you start using endoscopic. It's a 2D . Now, you don't have three dimension. You have to have some excellent technique for holding the endoscope, either four-handed technique with an assistant or a very good mechanical device to hold the endoscope. And you have to have very good surgical tools to do an endoscopic-assisted technique, or you do for any of the techniques, so. And you have to get the craniectomy or craniotomy just in the right place in order to get smaller openings. But it takes the same size opening to do an endoscopic technique as you're now doing with microscopic. But I do believe, based on my experience with pituitary surgery and other interior scope based work, that we can do a better job using the endoscope, but it takes a lot of experience and the learning curve is steep.

- Thank you.

- What are the pitfalls? Cerebellar retraction and not draining good amount of CSF. Sacrificing anything that comes on the way. If the anatomy doesn't look right and you may not be well oriented, I think it's best to stop rather than continue retracting and avulsing a bridging vein. And the most reason for inadequate decompression is inadequate exposure. Placing the retractor is wisely very important. A thin retractor, just inferior to the flocculus, one or two millimeters being off often can cause a lot of headaches. Aggressive manipulation of any nerve should be avoided. Intraneural nerves should be left alone. Overzealous use of Teflon should be avoided and irrigate before you close just to make sure the implant doesn't move. And obviously, wax on the way in, wax on the way out. And if the patients wake up and not feeling better, we know there's definitely a phenomena where the spasm gets better in a delayed fashion. How much do you quote the patients usually it takes for them to for sure know if the delayed improvement is because of that phenomena versus the fact that they are not gonna be true?

- Well, I've only re-operated on one of my own patients and that was one similar to what you showed today, where we padded a very large vertebral artery and I was convinced that we didn't get it adequately. It moved, so I went back and put a sling around it.

- And do you use steroids post-operatively?

- Inter-op.

- Inter-op. So, you don't continue it after surgery?

- Pamper them rapidly post-op. It's very important.

- Okay.

- So, you get all of the blood out and all of the air out, so we depress the head, remove the air, get the CSF very clear.

- Okay.

- Don't allow any leakage of blood after and during closing.

- Okay, how about if you have an unfortunate evidence of a CSF leak? Do you put a lumbar drain for a few days and then if they-

- No.

- Go ahead.

- No, I wouldn't do that.

- You just go straight to exploring it again.

- Well, I would... If it's leaking underneath the incision and is contained, I'd watch it. If it's leaking to the outside, I put a couple of sutures in and watch it. If the CSF pressure is high and that's causing the leak, I probably would do a spinal tap for a couple of consecutive days. But I'd never put a drain in for a patient for this procedure or for a trigeminal.

- Okay, or the lumbar drain for rhinorrhea. For the skin, wound and drainage are obviously-

- I feel if you're having rhinorrhea, you might as well go back and close it.

- Okay, so you don't mess around with a lumbar drain?

- Right.

- You said you have done only one re-operation. But you do believe if the spasms don't go away after a few months, depending on what you found in surgery, you may go for a re-exploratory surgery?

- Oh, I've done a lot of re-operations, but I said only on one of my patients. But I re-operated in... I think if you think that you didn't do the job correctly, you should go back quickly because delaying a long period of time is not going to make the second operation any easier.

- Okay. Well, I would really like to thank you for your very expert thoughts in terms of teaching me personally and all viewers. Again, thank you again and we look forward to having another session with you in the future, John. Thank you again.

- Thanks a lot, Aaron. Very good job.

- Thank you.

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