Grand Rounds-Supratentorial Arteriovenous Fistulas: Nuances of Technique for Microsurgical Ligation

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- Hello, ladies and gentlemen, we're honored today to have with us, Dr. Johnny Delashaw, who is the new chairman at University of California, Irvine. Our discussion will be in two parts. The first part will be discussion regarding Microsurgical Management of Supratentorial Arteriovenous Fistulas. The second part which will be a separate session, we'll review the details regarding management of Infratentorial Arteriovenous Fistulas. and more specifically superior petrosal sinus AV fistulas. Johnny, thanks you for joining us. I'm gonna go ahead and briefly review a case just to get excited about our presentation today and show the associate surgical video. First let's go ahead and review the disclosures of the presenters that you can see. This is a 52 year old male with a sudden onset of headache who presented to the ER a few days later. So the presentation of this individual was rather in a delayed fashion and that could potentially affect the distribution of blood along the head CT, as you can see, there is some blood along the Sylvian fissure. However, a cerebral angiogram would reveal this abnormal connection along the olfactory tract potentially, and the ethmoid area from an artery directly to a cortical vein. So this would be consistent with an ethmoidal or two venous fistula. Let's go ahead and review the 3D angiogram for this patient, which could potentially better illustrate the details of the anatomy. As you can see in this 3D presentation, this is the carotid artery and MC ECM. You can see along the crista Galli, there is this abnormal connection, the artery to vein the cortical vein right there, and this 3d anatomy, really, as you can see, further looking forward above the eyes here, the location of the fistula, as you know, the finding of this patient would lead us believe treatment is indicated due to the fact that the fistula does have cortical venous drainage and could potentially place the patient at the future risk of cerebral hemorrhage over further cerebral hemorrhages. Let's go ahead and review the surgical video in this case. So we did this case through an eyebrow incision or a supraciliary incision, Johnny, and placed the patient and made the opinion turn the head about 30 degrees contralaterally, rather than going through the incision behind a hairline because this hairline was very far back anyways, we use a supraciliary incision, as you can see here, and not necessarily in the eyebrow because of the risk of alopecia due to coagulating the skin edges. Do you like this approach for these lesions?

- [Johnny] I think this is a very reasonable approach, particularly for the gentleman's hairline. It's not one I typically use, but for the hairline, I think it's very reasonable.

- [Aaron] I appreciate it. So you would have considered this in this situation because of his hairline.

- [Johnny] Yes.

- [Aaron] As you can see, we go ahead and I use a microscope because we want to preserve the nerves, the supra orbital nerve, as you can see here, which really limits us medially in our incision and use a colorado needle on the bovie, not to bovie materials or the orbicularis oris muscle, and then laterally, we're going to be really going as much as necessary a little bit beyond the eyebrow and under the microscope, you can appreciate the branches of the frontallis nerve and the soft tissue that is over the temporalis muscle. So at this juncture, we want to definitely pay attention to the frontalis nerve. And we're going to focus on it in a second to better define the nerve. It is focusing down. And as you can see in a second those are the branches of the frontalis nerve that obviously have to be preserved to prevent any cosmetic deformity because a frontalis palsy. Any other details you would consider important here, Johnny?

- [Johnny] No, this kind of craniotomy, again, it limits your needle extension by the supraorbital nerve, but again, you want to find the keyhole which you're doing now and then turn a small flap involving the orbital rim so you can get underneath the brain and come down and find that I'm wrongly draining vein.

- [Aaron] Okay. And here you can see this small craniotomy, just you placing a burrow hole in the keyhole and sorta just turning the craniotomy and staying just along the orbital roof. Obviously the frontal sinus can be a limitation and most often the frontal sinus is also medial to the supraorbital nerve. So you're going to stay lateral to it anyways Here is again the 3D CT angiogram, just to situate ourselves where we're gonna go. We remove the craniotomy here and we're going to go just, a very much medial and not necessarily posterior just to find the fistula. And here is after the dura has been opened in it curving your fashion. We lift up the frontal lobe and again, not going posteriorly, but more medially. And I have to mention that we do place a lumbar drain on these patients prior to performing the craniotomy before their positioned. And as we open the dura, we relieve some of the CSF to achieve more frontal lobe relaxation. Here you can see we can immediately appreciate crista galli and the dura along the frontal. And you can see a more normal looking vein and a more arterialized vein coming from ethmoid area to the brain as well as you can see some of the leaflets of the duras that are expanded. And that's what we really define as the fistula and coagulated and cut the connections. Any thoughts here Johnny?

- [Johnny] No, that's exactly what you want to do. You want to include venous outflow and the dural fistula, then go ahead and include itself. That's all that's necessary in these. And it's a nice procedure prevents intercranial hemorrhage.

- {Aaron] Right. And you can see the fistulas connections are actually in the dura and that's what we coagulated as well. And here is just using many plates. We use crany fixed medially because we don't want to place a screw into the frontal sinus and cause a CSF leak. And afterwards the layers are closed in atomic layers, a liberal method on the sacral leg, may be performed just to cause or achieve a good cosmetic results. Obviously the periosteum and the muscle layers are closed in one layer to make sure there is no ptosis. And then three or four microsutures are used along the more superficial layers to make sure the skin heals well. Any other pointers Johnny on this approach please?

- [Johnny] No, I don't think so. I think it's very well covered. It's a nice approach. Quickly gets there. Quickly closes patients should be in the hospital very short length of time. Minimal brain retraction.

- [Aaron] Thank you. I agree, but definitely brings about its own limitation which is a limited space to work with. If you have a ruptured aneurysm that you're doing through this approach, if you have interrupted rupture, there is no space for a third sucker and really there's no lateral trajectory to work through. You're really working through an anterolateral and most of the anterior trajectory. Do you agree?

- [Johnny] Yes. I think if you need extension laterally, it's going to be difficult.

- [Aaron] Okay. And I'm going to briefly mention some general discussions before we proceed to your valuable slides today that do all twin fistulas are abnormal connections between an arterial feeder and a dual venous sinus or leptomeningeal vein with the sinus located within the dural leaflets. That's the definition of a dural AV fistula to compose about 10 to 15% of ASCO malformations, and then the supratentorial space. Most of them are ethmoidal, although the ethmoidal fistulas can be on both sides and that's an important nuance for their management. So you have to realize that before surgery, before you proceed with their disconnection and parasagittal sphenoparietal sinus dural arteriovenous fistulas, or also other classes of supratentorial AV fistula and really the other classes of supratentorial AV fistulas are extremely rare. So with that introduction, let's go ahead and start your presentation today, Johnny, which I'm very excited to listen to.

- Thank you. Well, what I've been asked to do today is talk about dural AV fistulas. And what I like to do is talk a little bit about what exactly it is as Dr. Cohen has, has mentioned. It's an abnormal direct shot between the dural arterial supply and the dural venous system. Its thought to be acquired. Many of these patients have a history of trauma, most common dural fistulas located in the region of the transverse and sigmoid sinus or at the cavernous carotid fistula. Here's a, a angiogram showing a fistula here, complex fistula involving the transverse sinus. So the dural AV fistulas symptoms that are most common are actually headache is the most common followed by a bruit. Many of the patients, when they have a dural fistula complain of a sound, a whooshing sound in their head, they can develop cranial nerve deficits, particularly in the posterior fossa dural AV fistula or they can present with hemorrhage. Here's a patient who actually is a cardiologist who presented to us with subarachnoids and interventricular hemorrhage related to a dural AV fistula. Okay. There are types of dural AV fistulas I'd like to talk about, particularly the trans or sigmoid sinus. Again, one of the most common the one of the dural AV fistulas is a normal antegrade flow through the transverse sinus to the jugular vein so that the arterial supply goes right to the sinus and its normal flow. There's another kind of dural AV fistula where you see normal flow, and then you also see retrograde flow through the transfer sinus. The third type is antegrade or retrograde flow through the sinus with cortical drainage. That becomes a more dangerous dural AV fistula related to development of a subarachnoids hemorrhage or intraparenchymal hemorrhage because of the cortical drainage. And then the one that's very dangerous is the one that flows only into the cortical veins. The normal antegrade flow in the transverse sinus, the risk of hemorrhage or stroke is very low. They primarily complain of a bruit. We only treat those if their symptoms are intolerable, we typically use our arterial embolization for these are, we occasionally include the sigmoid sinus if the patient has excellent flow from the sagittal sinus to the opposite transverse sinus, but this is primarily to treat Ruiz and tolerable sound. It's not meant to reduce risk of hemorrhage or strokes since its so low. For the next type of the transverse sigmoid sinus AV fistula The involved Sigma sentence can be taken with embolization, usually in coils. This is because there's antegrade and retrograde flow. It's very important that the veins of Labbe are not embolized themselves, but we can, embolize just near them. If a dural AV fistula is located near the vein of Labbe, then we may need to consider arterial embolization rather than being a symbolization for those dural AV fistulas that have antegrade and or retrograde flow through the sinus with cortical venous drainage. These are ones we are very concerned about. There's a high risk of stroke or hemorrhage transarterial embolization is done if possible, and we need to consider surgical resection by occlusion of the fistula from the cortical venous drainage. Here's an example, here's a Dural AV fistula where a patient presented to us with an embolic. I'm sorry, with a sound, a wooshing sound in the head. And we were concerned about the development of a stroke or a hemorrhage, because we thought this was high risk. The, as you look here, there is this fistula that has some abnormal cortical venous drainage. This is the dural AV fistula that we had just showed on the angiogram. And what I'd like to show you first is that there's, this is a CTA, and you can see this dural AV fistula here with the CTA. We use that to do frameless characteristic guidance. So we can make a very small craniotomy and come down onto the abnormal cortical vein it's being drained into from this dural AV fistula. And here's that vein right here. All we did was we took an aneurysm clip, placed it over the area. And as you can see by doing that, that once we did that, the vein turns immediately blue, dark red blue, showing that the critical venous drainage has now been separated from the rest of the dural fistula. The remaining dural fistula will clot off on its own. We put another aneurysm clip on and then ligated between the two and got an excellent result. Cortical venous drainage only dural AV fistulas are thought to be very high risk for stroke and may represent progression of sinus thrombosis. And again, just like the diagram and movie I showed you before surgery is a definitive therapy. Now moving on to ones that are more interesting for surgery, the superior petrosal sinus dural AV fistula is typically more on the right side than it is on the left. They frequently present with hemorrhage. When they do present hemorrhage, when you ask the patient, they frequently say: "Hey I also had a bruit sound in my ear" Sometimes they present only with a bruit sign or a cranial nerve deficit, but frequently present with hemorrhage. Here's again, this cardiologist that I was talking about, who presented with a intrapretricolor in subarachnoids hemorrhage. As you can see here on these two CT scans, can we show the, get ready to show the movie? Here's a CTA showing this dural fistula here with this aneurysm, this is of the venous system. You can see it here on the lateral view, and this is where we need to stop the venous outflow. So we want to stop the arterial venous outflow, right at the superior petrosal sinus. And this will result in occlusion of the dural AV fistula. So you see this diagram here, we've actually come down doing a small suboccipital craniectomy and come down and find this large petrosal vein thats part of the fistula. And what you would do is put a clip over this. Then you can see how bloody it is because there's acute subarachnoids hemorrhage. We're going to talk more about the petrosal sinus dural AV fistula in another talk, which you're welcome to look on the internet and see. Let's go ahead and move to the ones above and the supratentorial region. Here's a diagram showing that aneurysm clip we'll move to the ones in the supratentorial region. And that is again, similar to what Dr. Cohen has showed the anterior ethmoid sinus dural Av fistula. Here's a gentleman who presented with a hemorrhage and a large dural AV fistula. You can see the barracks here of related to the dural fistula being fed by the anterior ethmoidal's. Again, this'll be located right near the crista galli, on the anterior fossa floor, you can see this varix section coming over to the opposite side, being fed by, by both the supplies of arterials from the right and left. A super orbital craniotomy was then performed. And by doing that, we can now see this Varix here. And we can see this large FMO vein really coming from the arterial supply. And again, the key here on these dural fistulas is to include venous outflow. So what we did was we put a clip right on the floor of the anterior fossa, right at this vein, right along the dura. And then we can ligate it and cut it, and the dural fistula is now taken care of. You can see actually this varix has now gotten quite soft. And this is the treatment of choice, including the venous outflow. I must admit this was done by my colleague Dr. Ashlynn Dhawan, who works with me in our vascular program here at OHSU. Here's a postoperative view of the angiogram showing that no longer is the dural AV fistula filling. Patient did extremely well. Another type of dural AV fistula is one located around the sagittal sinus. This is not nearly as common superior petrosal dural AV fistula. And the after ethmoidal dural AV fistulas are far more common. The sagittal sinus dural AV fistula do occur though, and they can present again with hemorrhage and headache. Here's a patient who has a complex one located along the fox here being fed by the meningeal artery. And there you have this complex dural AV fistula. So we've done a parietal occipital craniotomy, and we're looking down along the Fox. This is the right brain here. This is the edge of the false we flip the dural over. You can see this abnormal collection of veins, which is part of the dural AV fistula. Now the treatment of this is we want to occlude venous outflow. Remember the drone officials coming from arterial supply within the dura. And as it comes in, it comes out through these cortical veins and actually is flowing the wrong direction, putting the cortical veins at risk. So you want to expose this area and then you can slowly coagulate it until you can define an area where you can put an aneurysm clip on and ligate the area. You can just use coagulation, but I like to use an aneurysm clip it just feels, I just feel more secure about it. If you separate this area from the cortical veins, the, the fistula will go on to occlude itself. And that's a very simple treatment for these more dangerous dural fistulas that can cause stroke or hemorrhage. Now, one of the things about this particular dural fistula is sometimes you get into a little bit of bleeding just to get there. You can have some scalp, scalp feeders that actually feed into the dural fistula through the skull. And so you have to be a little bit careful about your incision. And as you, as you do this surgery, you can just simply take the arterial supply on the scalp, which is actually very, very simple, but it can cause some significant bleeding if you're not aware of it. Turning the bone flap, you want be careful to stay up in the dural plain, to prevent yourself from getting into trouble with these cortical veins that are abnormal right on the surface. Here we have one that's still bleeding. We coagulate it carefully right at the origin of the cortical vein itself. And what we're going to do ultimately is skip this narrow down to be put an aneurysm clip both along the Fox. And along this cortical vein. This was again, this operation here, this particular one, Dr. Dhawan who's again, my colleague is the one bipolaring here and separating the dural fistula. His cut the cortical vein connection, his checking to get a little bit better control with the bipolar. It's now separated. This is Dr. Cohen had done earlier in the other dural fistula were coagulating any small fears within the dura that are easy to coagulate with the bipolar. But there is a complete separation of the fistula from the brain. And just to be extra careful, replacing an aneurysm clip on the cortical vein edge, and we'll place one more aneurysm clip right along the Fox. And you can see in the postoperative angiogram, here is a AP view and here's a lateral view. The fistula is no longer filling. Dr Cohen I think this is an excellent example of what we need to do surgically with these dural fistulas that are surgically operable. These are much easier to take care of with surgery than they are with, with an embolization technique. The reason why that is, is the primary treatment for a dural fistula is to include venous outflow with an anterior ethmoidal fistula It's very hard to get venous access to the fistula. It's also hard to get arterial access because one would have to embolize the ethmoidal arteries up to the vein. And that would require insertion of a catheter into the ophthalmic artery, which would put high risk for blindness. So surgery really the only effective treatment for the anterior ethmoidal dural AV fistulas. For the sagittal sinus fistulas, again it would be very difficult to embolize through the venous structures, which is the way the best treatment is for these dural fistulas and surgery is such as surgery is the primary choice for the transverse sinus fistula. So it can be a complex fistula surgery can be very important if there's cortical drainage primarily and aiding embolization technique through the transverse sinus by an interventional group is the usual way for those more or less dangerous dural fistulas.

- [Aaron] Thank you Johnny. I appreciate your, your very nice presentation and really pros of technique. If you don't mind, I would like to present one or two more cases and please feel free to comment and criticize as you see fit. Again, another case of supratentorial AV fistula, 72 year old male, with a sudden onset of left upper extremity weakness, which resolved over about one month. He had evaluation in an outside hospital. Again, the initial CT revealed evidence of a hemorrhage. And as you can see, an MRI was performed to better analyze the etiology and varix was also suspected and intracranial angiogram, as you can see is completely negative. And this is another important point that often can be a board question that four 80 fistulas. And if someone has an spontaneous intracranial hemorrhage, more importantly, you have to evaluate both internal and external vessels off of the carotid artery. Otherwise, if you look at the internal carotid artery circulation, it looks absolutely normal. And you would say, I didn't find a cause for a hemorrhage. And it's until you do an external injection that you really find this very impressive AV fistula that is coming from the middle meningeal branches, as you can see there, and really forming a very complex varix. The varix itself can be very scary, but you have to realize these have very small two, three, you know fistulas connections through the dural meningeal feeders, and their disconnection really causes an amazing relief of these giants varices.

- The importance for the viewers is that it's not important to take care of the varix. It's important to take care of the connection between the Fox and the sinus and the cortical veins at that edge. If you disconnect there, the varix will become very relaxed, and ultimately will clot off. So it's very important not to worry so much about the varix but all you really want to do is stop venous outflow disconnect the venous outflows to the cortical venous drainage.

- Thank you, Johnny. I think that's a very important point because if you try to really play with the veins, you may cause more injury than anything else. So let's go ahead and review the video in this case, as you can see, this is a right sided parietal craniotomy patient position, your lateral position, and this is the dural over the superior sagittal sinus. You can see a vein here and really the fistula is not very obvious, but you can see the large varix here. Again. This is the edge of the Fox. Johnny what I have found interesting is you can use ICG and see the fistulas connection, which is arterialized before the normal vein. So the ICG can actually provide you with a method of delineating an arterialized vein versus a normal vein by then, timing of their filling with the die. So here, this is a normal vein. This is the fistulas connection because this filled out earlier and also it is connected to the dural over the sinus. So we went ahead here and dissected the brain off of the dural over the super sagittal sinus. And you can see a small fistulas connection here. This was better defined as we mobilize more of the two super sagittal sinus. And you can see the fistulas connection here. Any other thoughts, Johnny?

- [Johnny] No, I think that technique using an angiography or CT angiography is terrific. Sometimes these can be very complex about which is the fistula and which is a normal vein. It may also be helpful in spinal too and I'm not sure I've not tried that.

- [Aaron] Thank you. And as you can see here, there is that fistulas large fistulas connection going into the dural over the sinus. This looks like more of a normal vein. And again, that was the same vein that we excluded using in top of ICG angiogram that you briefly mentioned, and ultimately you may coagulate or cut, or in certain situation, I make my job a little bit easier. I just put a clip across it and I'll do another ICG. And the ICG can define if the whole varix has been deflated and there is no further fresh filling with the dye. Obviously there will be some filling because there was some dye before, as we're trying to differentiate, which one is the fistula, but the fresh dye is pretty obvious and easily recognizable against the older dye in the vessels. And here is really placing that clip across. And you may appreciate that the varix on the cortex of the brain has already been deflated just very well nicely showed in your video.

- [Johnny] No, I would recommend an aneurysm clip. You can clip because it's going to take a little while for the fistula to completely occlude more proximately. And I think it's just a little bit safer to have that clip on.

- [Aaron] Okay. And you can see the vein Johnny was very blue by the end of our placement of a aneurysm clip. And you can see there is no fresh dye in the varix, whatever it is is really the old dye that is stagnant.

- [Johnny] That's true.

- [Aaron] When we felt that this fistula. Thank you. We felt that this fistula was very adequately treated until we did the postoperative angiogram. And this is something that I want to discuss because I think it's easy to feel very victorious and say, well, I think I got it done, but actually when you try to do the post-operative angiogram, you may be surprised. And here it is the postoperative... actually, this was the intraoperative angiogram Johnny showing that there was no fistulas connection. And we were happy that we did the job. And then we did a post-op angiogram a day later. And you can see these again fistulas connections And in these large fistulas. I think if you disconnect one, you may find out that the smaller ones that were not very clear on the initial preoperative angiogram start gaining some attention because their flow has been changed. Is this the way you think why we have a residual fistula, Johnny? What are your thoughts there?

- Well, I think on the sagittal sinus fistulas, it can be a little bit more complex. They don't always have just one venous outflow. Like the anterior ethmoid tends to have one venous outflow and superior petrosal sinus one, which is really the most common tends to have one venous outflow through petrosal vein system. So they can be a little more complicated. You know, it may not be filling very well because it has, most of its flow is through that other area with the varix and you can't see it, but it is probably always there. And I think doing a postoperative angiogram is required for these, to be absolutely sure that you've taken care of the entire fistula.

- Thank you, Johnny. And again, they went ahead and embolized that residual fistula. And as you can see, after some glue was placed on that smaller portion of this fistula, this fistula was cured. So as for most of our vascular cases these days, and multidisciplinary microsurgical and endovascular treatment seems to be the key to success. And let's just briefly review some pearls and pitfalls for these supratentorial fistulas Johnny. That endovascular therapy remains a good option for still some of these lesions. You did mention that for ethmoidal's because their branches are ophthallmic artery. Gluing the ethmoidal feeders to the AV fistula can place their retinal artery off of the ophthallmic artery at risk. And therefore endovascular option is not highly recommended. And therefore surgery remains a very good choice. For the parasagittal ones, I think endovascular does play a good role, but again, the surgery, show no risk. That you have to fashion every treatment based on the individual patient. What are your thoughts about endovascular embolization in expectation of surgery Johnny? Do you think that has a role?

- So here are my thoughts for the three types of the three types of surgical Dural AV fistulas is that surgery is the primary choice. That is the superior petrosal sinus dural fistula again, the posterior fossa, the most common, Anterior ethmoidal clearly a surgical treatment because of the risk of embolization is so high. The sagittal sinus one is not very common, but again, surgery is a direct approach and usually very, very simple. The embolization, what they use now is Onyx and they can embolize the arterial supply. But remember the primary treatment is not embolization of the arterial supply. It's occlusion of venous outflow, and it can be a little bit risky to do that because one could get glue into the sagittal sinus. So again, surgery is still the primary treatment for sagittal sinus dural AV fistulas for the more complex dural fistulas are the cavernous sinus, the CC fistula, or for the transverse sinus fistulas that don't have significant cortical venous drainage, an endovascular approach is the primary approach.

- Thank you. And just to remind our viewers that review of the cases today was primarily those that are amenable to surgical therapy and they're safer using the surgical approach. And there are many other ones supratentorially just like you very well mentioned the cavernous, the CC fistulas that we have super in last therapies at this time and therefore you're no longer surgically tackle at least more often. I guess the other issue is the speed of providal AV fistulas those are in rare and also surgically can be amenable along the middle fossa. And again, the most common AV fistula supratentorial are really ethmoidal's and the parasagittal ones. And I think the other nuances, if you have problems finding the fistula intraoperatively, it's really easy to press a clip of adjacent to the sinus, to the suprasagittal sinus, where you think the fistula could be, and then do an intraopretive angiogram and identify where's the fistulas connection in relationship to your clip. I think that would help tremendously or do an ICG. Just we demonstrated it. and again, the chance of recurrence does exist and these patients have to be followed carefully. Johnny, do you have any other closing statements for this session as we're going to have his next session talking about more specifically posterior fossa AV fistulas?

- Well, the only thing I would say other than what you've very well said today is for the surgical exposure of those parasagittal dural AV fistulas involved in the sagittal sinus and the cortical veins, CT angiography with frameless charecter can really help you in designing an incision, designing a craniotomy that's small and direct right to the fistula. And so I'd highly recommend that that be done as part of your surgical planning. For the anterior ethmoidal one, it's very simple where it is don't need a CT angiogram to provide you with planning. It's right there along the crista galli, very easy to find and for the superior petrosal one which again, we're going to talk about in another session again, you really don't need a frameless detected guidance to find that fistula either, but for the sagittal sinus ones it's can be very, very helpful. Other than that, I don't have really any other thing to say. I think it's been well said, and I hope that the viewer has found some information that they can take back to the practice and treat their patients effectively.

- Thank you very much, Johnny, for your expert opinion.

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